xref: /btstack/src/classic/avrcp.c (revision 6b7adbe5dd4b0af3c7d33d07ce150d2f4a3a18e0)
1 /*
2  * Copyright (C) 2016 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 #define __BTSTACK_FILE__ "avrcp.c"
39 
40 #include <stdint.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 
45 #include "btstack.h"
46 #include "classic/avrcp.h"
47 
48 #define PSM_AVCTP                       BLUETOOTH_PROTOCOL_AVCTP
49 #define PSM_AVCTP_BROWSING              0x001b
50 
51 /*
52 Category 1: Player/Recorder
53 Category 2: Monitor/Amplifier
54 Category 3: Tuner
55 Category 4: Menu
56 */
57 
58 /* controller supported features
59 Bit 0 = Category 1
60 Bit 1 = Category 2
61 Bit 2 = Category 3
62 Bit 3 = Category 4
63 Bit 4-5 = RFA
64 Bit 6 = Supports browsing
65 Bit 7-15 = RFA
66 The bits for supported categories are set to 1. Others are set to 0.
67 */
68 
69 /* target supported features
70 Bit 0 = Category 1
71 Bit 1 = Category 2
72 Bit 2 = Category 3
73 Bit 3 = Category 4
74 Bit 4 = Player Application Settings. Bit 0 should be set for this bit to be set.
75 Bit 5 = Group Navigation. Bit 0 should be set for this bit to be set.
76 Bit 6 = Supports browsing*4
77 Bit 7 = Supports multiple media player applications
78 Bit 8-15 = RFA
79 The bits for supported categories are set to 1. Others are set to 0.
80 */
81 
82 static uint16_t avrcp_cid_counter = 1;
83 
84 // TODO: merge with avdtp_packet_type_t
85 typedef enum {
86     AVRCP_SINGLE_PACKET= 0,
87     AVRCP_START_PACKET    ,
88     AVRCP_CONTINUE_PACKET ,
89     AVRCP_END_PACKET
90 } avrcp_packet_type_t;
91 
92 typedef enum {
93     AVRCP_COMMAND_FRAME = 0,
94     AVRCP_RESPONSE_FRAME
95 } avrcp_frame_type_t;
96 
97 static int record_id = -1;
98 static uint8_t   attribute_value[1000];
99 static const unsigned int attribute_value_buffer_size = sizeof(attribute_value);
100 
101 static const char * default_avrcp_controller_service_name = "BTstack AVRCP Controller Service";
102 static const char * default_avrcp_controller_service_provider_name = "BTstack AVRCP Controller Service Provider";
103 static const char * default_avrcp_target_service_name = "BTstack AVRCP Target Service";
104 static const char * default_avrcp_target_service_provider_name = "BTstack AVRCP Target Service Provider";
105 
106 static btstack_packet_handler_t avrcp_callback;
107 
108 static avrcp_context_t avrcp_controller_context;
109 
110 static const char * avrcp_subunit_type_name[] = {
111     "MONITOR", "AUDIO", "PRINTER", "DISC", "TAPE_RECORDER_PLAYER", "TUNER",
112     "CA", "CAMERA", "RESERVED", "PANEL", "BULLETIN_BOARD", "CAMERA_STORAGE",
113     "VENDOR_UNIQUE", "RESERVED_FOR_ALL_SUBUNIT_TYPES",
114     "EXTENDED_TO_NEXT_BYTE", "UNIT", "ERROR"
115 };
116 const char * avrcp_subunit2str(uint16_t index){
117     if (index <= 11) return avrcp_subunit_type_name[index];
118     if (index >= 0x1C && index <= 0x1F) return avrcp_subunit_type_name[index - 0x10];
119     return avrcp_subunit_type_name[16];
120 }
121 
122 static const char * avrcp_event_name[] = {
123     "ERROR", "PLAYBACK_STATUS_CHANGED",
124     "TRACK_CHANGED", "TRACK_REACHED_END", "TRACK_REACHED_START",
125     "PLAYBACK_POS_CHANGED", "BATT_STATUS_CHANGED", "SYSTEM_STATUS_CHANGED",
126     "PLAYER_APPLICATION_SETTING_CHANGED", "NOW_PLAYING_CONTENT_CHANGED",
127     "AVAILABLE_PLAYERS_CHANGED", "ADDRESSED_PLAYER_CHANGED", "UIDS_CHANGED", "VOLUME_CHANGED"
128 };
129 const char * avrcp_event2str(uint16_t index){
130     if (index <= 0x0d) return avrcp_event_name[index];
131     return avrcp_event_name[0];
132 }
133 
134 static const char * avrcp_operation_name[] = {
135     "NOT SUPPORTED", // 0x3B
136     "SKIP", "NOT SUPPORTED", "NOT SUPPORTED", "NOT SUPPORTED", "NOT SUPPORTED",
137     "VOLUME_UP", "VOLUME_DOWN", "MUTE", "PLAY", "STOP", "PAUSE", "NOT SUPPORTED",
138     "REWIND", "FAST_FORWARD", "NOT SUPPORTED", "FORWARD", "BACKWARD" // 0x4C
139 };
140 const char * avrcp_operation2str(uint8_t index){
141     if (index >= 0x3B && index <= 0x4C) return avrcp_operation_name[index - 0x3B];
142     return avrcp_operation_name[0];
143 }
144 
145 static const char * avrcp_media_attribute_id_name[] = {
146     "NONE", "TITLE", "ARTIST", "ALBUM", "TRACK", "TOTAL TRACKS", "GENRE", "SONG LENGTH"
147 };
148 const char * avrcp_attribute2str(uint8_t index){
149     if (index >= 1 && index <= 7) return avrcp_media_attribute_id_name[index];
150     return avrcp_media_attribute_id_name[0];
151 }
152 
153 static const char * avrcp_play_status_name[] = {
154     "STOPPED", "PLAYING", "PAUSED", "FORWARD SEEK", "REVERSE SEEK",
155     "ERROR" // 0xFF
156 };
157 const char * avrcp_play_status2str(uint8_t index){
158     if (index >= 1 && index <= 4) return avrcp_play_status_name[index];
159     return avrcp_play_status_name[5];
160 }
161 
162 static const char * avrcp_ctype_name[] = {
163     "CONTROL",
164     "STATUS",
165     "SPECIFIC_INQUIRY",
166     "NOTIFY",
167     "GENERAL_INQUIRY",
168     "RESERVED5",
169     "RESERVED6",
170     "RESERVED7",
171     "NOT IMPLEMENTED IN REMOTE",
172     "ACCEPTED BY REMOTE",
173     "REJECTED BY REMOTE",
174     "IN_TRANSITION",
175     "IMPLEMENTED_STABLE",
176     "CHANGED_STABLE",
177     "RESERVED",
178     "INTERIM"
179 };
180 const char * avrcp_ctype2str(uint8_t index){
181     if (index < sizeof(avrcp_ctype_name)){
182         return avrcp_ctype_name[index];
183     }
184     return "NONE";
185 }
186 
187 static const char * avrcp_shuffle_mode_name[] = {
188     "SHUFFLE OFF",
189     "SHUFFLE ALL TRACKS",
190     "SHUFFLE GROUP"
191 };
192 
193 const char * avrcp_shuffle2str(uint8_t index){
194     if (index >= 1 && index <= 3) return avrcp_shuffle_mode_name[index-1];
195     return "NONE";
196 }
197 
198 static const char * avrcp_repeat_mode_name[] = {
199     "REPEAT OFF",
200     "REPEAT SINGLE TRACK",
201     "REPEAT ALL TRACKS",
202     "REPEAT GROUP"
203 };
204 
205 const char * avrcp_repeat2str(uint8_t index){
206     if (index >= 1 && index <= 4) return avrcp_repeat_mode_name[index-1];
207     return "NONE";
208 }
209 static void packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size, avrcp_context_t * context);
210 
211 static avrcp_sdp_query_context_t sdp_query_context;
212 static void avrcp_handle_sdp_client_query_result(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
213 
214 static void avrcp_create_sdp_record(uint8_t controller, uint8_t * service, uint32_t service_record_handle, uint8_t browsing, uint16_t supported_features, const char * service_name, const char * service_provider_name){
215     uint8_t* attribute;
216     de_create_sequence(service);
217 
218     // 0x0000 "Service Record Handle"
219     de_add_number(service, DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_SERVICE_RECORD_HANDLE);
220     de_add_number(service, DE_UINT, DE_SIZE_32, service_record_handle);
221 
222     // 0x0001 "Service Class ID List"
223     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_SERVICE_CLASS_ID_LIST);
224     attribute = de_push_sequence(service);
225     {
226         if (controller){
227             de_add_number(attribute, DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL);
228             de_add_number(attribute, DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_CONTROLLER);
229         } else {
230             de_add_number(attribute, DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_TARGET);
231         }
232     }
233     de_pop_sequence(service, attribute);
234 
235     // 0x0004 "Protocol Descriptor List"
236     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_PROTOCOL_DESCRIPTOR_LIST);
237     attribute = de_push_sequence(service);
238     {
239         uint8_t* l2cpProtocol = de_push_sequence(attribute);
240         {
241             de_add_number(l2cpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_L2CAP);
242             de_add_number(l2cpProtocol,  DE_UINT, DE_SIZE_16, BLUETOOTH_PROTOCOL_AVCTP);
243         }
244         de_pop_sequence(attribute, l2cpProtocol);
245 
246         uint8_t* avctpProtocol = de_push_sequence(attribute);
247         {
248             de_add_number(avctpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_AVCTP);  // avctpProtocol_service
249             de_add_number(avctpProtocol,  DE_UINT, DE_SIZE_16,  0x0103);    // version
250         }
251         de_pop_sequence(attribute, avctpProtocol);
252     }
253     de_pop_sequence(service, attribute);
254 
255     // 0x0005 "Public Browse Group"
256     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_BROWSE_GROUP_LIST); // public browse group
257     attribute = de_push_sequence(service);
258     {
259         de_add_number(attribute,  DE_UUID, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_PUBLIC_BROWSE_ROOT);
260     }
261     de_pop_sequence(service, attribute);
262 
263     // 0x0009 "Bluetooth Profile Descriptor List"
264     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_BLUETOOTH_PROFILE_DESCRIPTOR_LIST);
265     attribute = de_push_sequence(service);
266     {
267         uint8_t *avrcProfile = de_push_sequence(attribute);
268         {
269             de_add_number(avrcProfile,  DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL);
270             de_add_number(avrcProfile,  DE_UINT, DE_SIZE_16, 0x0105);
271         }
272         de_pop_sequence(attribute, avrcProfile);
273     }
274     de_pop_sequence(service, attribute);
275 
276     // 0x000d "Additional Bluetooth Profile Descriptor List"
277     if (browsing){
278         de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_ADDITIONAL_PROTOCOL_DESCRIPTOR_LISTS);
279         attribute = de_push_sequence(service);
280         {
281             uint8_t * des = de_push_sequence(attribute);
282             {
283                 uint8_t* browsing_l2cpProtocol = de_push_sequence(des);
284                 {
285                     de_add_number(browsing_l2cpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_L2CAP);
286                     de_add_number(browsing_l2cpProtocol,  DE_UINT, DE_SIZE_16, PSM_AVCTP_BROWSING);
287                 }
288                 de_pop_sequence(des, browsing_l2cpProtocol);
289 
290                 uint8_t* browsing_avctpProtocol = de_push_sequence(des);
291                 {
292                     de_add_number(browsing_avctpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_AVCTP);  // browsing_avctpProtocol_service
293                     de_add_number(browsing_avctpProtocol,  DE_UINT, DE_SIZE_16,  0x0103);    // version
294                 }
295                 de_pop_sequence(des, browsing_avctpProtocol);
296             }
297             de_pop_sequence(attribute, des);
298         }
299         de_pop_sequence(service, attribute);
300     }
301 
302 
303     // 0x0100 "Service Name"
304     de_add_number(service,  DE_UINT, DE_SIZE_16, 0x0100);
305     if (service_name){
306         de_add_data(service,  DE_STRING, strlen(service_name), (uint8_t *) service_name);
307     } else {
308         if (controller){
309             de_add_data(service,  DE_STRING, strlen(default_avrcp_controller_service_name), (uint8_t *) default_avrcp_controller_service_name);
310         } else {
311             de_add_data(service,  DE_STRING, strlen(default_avrcp_target_service_name), (uint8_t *) default_avrcp_target_service_name);
312         }
313     }
314 
315     // 0x0100 "Provider Name"
316     de_add_number(service,  DE_UINT, DE_SIZE_16, 0x0102);
317     if (service_provider_name){
318         de_add_data(service,  DE_STRING, strlen(service_provider_name), (uint8_t *) service_provider_name);
319     } else {
320         if (controller){
321             de_add_data(service,  DE_STRING, strlen(default_avrcp_controller_service_provider_name), (uint8_t *) default_avrcp_controller_service_provider_name);
322         } else {
323             de_add_data(service,  DE_STRING, strlen(default_avrcp_target_service_provider_name), (uint8_t *) default_avrcp_target_service_provider_name);
324         }
325     }
326 
327     // 0x0311 "Supported Features"
328     de_add_number(service, DE_UINT, DE_SIZE_16, 0x0311);
329     de_add_number(service, DE_UINT, DE_SIZE_16, supported_features);
330 }
331 
332 void avrcp_controller_create_sdp_record(uint8_t * service, uint32_t service_record_handle, uint8_t browsing, uint16_t supported_features, const char * service_name, const char * service_provider_name){
333     avrcp_create_sdp_record(1, service, service_record_handle, browsing, supported_features, service_name, service_provider_name);
334 }
335 
336 void avrcp_target_create_sdp_record(uint8_t * service, uint32_t service_record_handle, uint8_t browsing, uint16_t supported_features, const char * service_name, const char * service_provider_name){
337     avrcp_create_sdp_record(0, service, service_record_handle, browsing, supported_features, service_name, service_provider_name);
338 }
339 
340 static void avrcp_emit_connection_established(btstack_packet_handler_t callback, uint16_t avrcp_cid, bd_addr_t addr, uint8_t status){
341     if (!callback) return;
342     uint8_t event[12];
343     int pos = 0;
344     event[pos++] = HCI_EVENT_AVRCP_META;
345     event[pos++] = sizeof(event) - 2;
346     event[pos++] = AVRCP_SUBEVENT_CONNECTION_ESTABLISHED;
347     event[pos++] = status;
348     reverse_bd_addr(addr,&event[pos]);
349     pos += 6;
350     little_endian_store_16(event, pos, avrcp_cid);
351     pos += 2;
352     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
353 }
354 
355 static void avrcp_emit_repeat_and_shuffle_mode(btstack_packet_handler_t callback, uint16_t avrcp_cid, uint8_t ctype, avrcp_repeat_mode_t repeat_mode, avrcp_shuffle_mode_t shuffle_mode){
356     if (!callback) return;
357     uint8_t event[8];
358     int pos = 0;
359     event[pos++] = HCI_EVENT_AVRCP_META;
360     event[pos++] = sizeof(event) - 2;
361     event[pos++] = AVRCP_SUBEVENT_SHUFFLE_AND_REPEAT_MODE;
362     little_endian_store_16(event, pos, avrcp_cid);
363     pos += 2;
364     event[pos++] = ctype;
365     event[pos++] = repeat_mode;
366     event[pos++] = shuffle_mode;
367     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
368 }
369 
370 static void avrcp_emit_operation_status(btstack_packet_handler_t callback, uint8_t subevent, uint16_t avrcp_cid, uint8_t ctype, uint8_t operation_id){
371     if (!callback) return;
372     uint8_t event[7];
373     int pos = 0;
374     event[pos++] = HCI_EVENT_AVRCP_META;
375     event[pos++] = sizeof(event) - 2;
376     event[pos++] = subevent;
377     little_endian_store_16(event, pos, avrcp_cid);
378     pos += 2;
379     event[pos++] = ctype;
380     event[pos++] = operation_id;
381     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
382 }
383 
384 static void avrcp_emit_connection_closed(btstack_packet_handler_t callback, uint16_t avrcp_cid){
385     if (!callback) return;
386     uint8_t event[5];
387     int pos = 0;
388     event[pos++] = HCI_EVENT_AVRCP_META;
389     event[pos++] = sizeof(event) - 2;
390     event[pos++] = AVRCP_SUBEVENT_CONNECTION_RELEASED;
391     little_endian_store_16(event, pos, avrcp_cid);
392     pos += 2;
393     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
394 }
395 
396 static avrcp_connection_t * get_avrcp_connection_for_bd_addr(bd_addr_t addr, avrcp_context_t * context){
397     btstack_linked_list_iterator_t it;
398     btstack_linked_list_iterator_init(&it, (btstack_linked_list_t *) &context->connections);
399     while (btstack_linked_list_iterator_has_next(&it)){
400         avrcp_connection_t * connection = (avrcp_connection_t *)btstack_linked_list_iterator_next(&it);
401         if (memcmp(addr, connection->remote_addr, 6) != 0) continue;
402         return connection;
403     }
404     return NULL;
405 }
406 
407 static avrcp_connection_t * get_avrcp_connection_for_l2cap_signaling_cid(uint16_t l2cap_cid, avrcp_context_t * context){
408     btstack_linked_list_iterator_t it;
409     btstack_linked_list_iterator_init(&it, (btstack_linked_list_t *)  &context->connections);
410     while (btstack_linked_list_iterator_has_next(&it)){
411         avrcp_connection_t * connection = (avrcp_connection_t *)btstack_linked_list_iterator_next(&it);
412         if (connection->l2cap_signaling_cid != l2cap_cid) continue;
413         return connection;
414     }
415     return NULL;
416 }
417 
418 static avrcp_connection_t * get_avrcp_connection_for_avrcp_cid(uint16_t l2cap_cid, avrcp_context_t * context){
419     btstack_linked_list_iterator_t it;
420     btstack_linked_list_iterator_init(&it, (btstack_linked_list_t *)  &context->connections);
421     while (btstack_linked_list_iterator_has_next(&it)){
422         avrcp_connection_t * connection = (avrcp_connection_t *)btstack_linked_list_iterator_next(&it);
423         if (connection->avrcp_cid != l2cap_cid) continue;
424         return connection;
425     }
426     return NULL;
427 }
428 
429 static void avrcp_request_can_send_now(avrcp_connection_t * connection, uint16_t l2cap_cid){
430     connection->wait_to_send = 1;
431     l2cap_request_can_send_now_event(l2cap_cid);
432 }
433 
434 static void avrcp_press_and_hold_timeout_handler(btstack_timer_source_t * timer){
435     UNUSED(timer);
436     avrcp_connection_t * connection = btstack_run_loop_get_timer_context(timer);
437     btstack_run_loop_set_timer(&connection->press_and_hold_cmd_timer, 2000); // 2 seconds timeout
438     btstack_run_loop_add_timer(&connection->press_and_hold_cmd_timer);
439     connection->state = AVCTP_W2_SEND_PRESS_COMMAND;
440     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
441 }
442 
443 static void avrcp_press_and_hold_timer_start(avrcp_connection_t * connection){
444     btstack_run_loop_remove_timer(&connection->press_and_hold_cmd_timer);
445     btstack_run_loop_set_timer_handler(&connection->press_and_hold_cmd_timer, avrcp_press_and_hold_timeout_handler);
446     btstack_run_loop_set_timer_context(&connection->press_and_hold_cmd_timer, connection);
447     btstack_run_loop_set_timer(&connection->press_and_hold_cmd_timer, 2000); // 2 seconds timeout
448     btstack_run_loop_add_timer(&connection->press_and_hold_cmd_timer);
449 }
450 
451 static void avrcp_press_and_hold_timer_stop(avrcp_connection_t * connection){
452     connection->continuous_fast_forward_cmd = 0;
453     btstack_run_loop_remove_timer(&connection->press_and_hold_cmd_timer);
454 }
455 
456 static uint8_t request_pass_through_release_control_cmd(avrcp_connection_t * connection){
457     connection->state = AVCTP_W2_SEND_RELEASE_COMMAND;
458     if (connection->continuous_fast_forward_cmd){
459         avrcp_press_and_hold_timer_stop(connection);
460     }
461     connection->cmd_operands[0] = 0x80 | connection->cmd_operands[0];
462     connection->transaction_label++;
463     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
464     return ERROR_CODE_SUCCESS;
465 }
466 
467 static inline uint8_t request_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed, uint8_t continuous_fast_forward_cmd, avrcp_context_t * context){
468     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, context);
469     if (!connection){
470         log_error("avrcp: could not find a connection.");
471         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
472     }
473     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
474     connection->state = AVCTP_W2_SEND_PRESS_COMMAND;
475     connection->command_opcode =  AVRCP_CMD_OPCODE_PASS_THROUGH;
476     connection->command_type = AVRCP_CTYPE_CONTROL;
477     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
478     connection->subunit_id =   AVRCP_SUBUNIT_ID;
479     connection->cmd_operands_length = 0;
480 
481     connection->continuous_fast_forward_cmd = continuous_fast_forward_cmd;
482     connection->cmd_operands_length = 2;
483     connection->cmd_operands[0] = opid;
484     if (playback_speed > 0){
485         connection->cmd_operands[2] = playback_speed;
486         connection->cmd_operands_length++;
487     }
488     connection->cmd_operands[1] = connection->cmd_operands_length - 2;
489 
490     if (connection->continuous_fast_forward_cmd){
491         avrcp_press_and_hold_timer_start(connection);
492     }
493 
494     connection->transaction_label++;
495     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
496     return ERROR_CODE_SUCCESS;
497 }
498 
499 static uint8_t request_single_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed){
500     return request_pass_through_press_control_cmd(avrcp_cid, opid, playback_speed, 0, &avrcp_controller_context);
501 }
502 
503 static uint8_t request_continuous_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed){
504     return request_pass_through_press_control_cmd(avrcp_cid, opid, playback_speed, 1, &avrcp_controller_context);
505 }
506 
507 static int avrcp_send_cmd(uint16_t cid, avrcp_connection_t * connection){
508     uint8_t command[30];
509     int pos = 0;
510     // transport header
511     // Transaction label | Packet_type | C/R | IPID (1 == invalid profile identifier)
512     command[pos++] = (connection->transaction_label << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_COMMAND_FRAME << 1) | 0;
513     // Profile IDentifier (PID)
514     command[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
515     command[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
516 
517     // command_type
518     command[pos++] = connection->command_type;
519     // subunit_type | subunit ID
520     command[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
521     // opcode
522     command[pos++] = (uint8_t)connection->command_opcode;
523     // operands
524     memcpy(command+pos, connection->cmd_operands, connection->cmd_operands_length);
525     pos += connection->cmd_operands_length;
526 
527     return l2cap_send(cid, command, pos);
528 }
529 
530 static int avrcp_register_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t event_id){
531     if (connection->notifications_to_deregister & (1 << event_id)) return 0;
532     if (connection->notifications_enabled & (1 << event_id)) return 0;
533     if (connection->notifications_to_register & (1 << event_id)) return 0;
534     connection->notifications_to_register |= (1 << event_id);
535     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
536     return 1;
537 }
538 
539 static void avrcp_prepare_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t event_id){
540     connection->transaction_label++;
541     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
542     connection->command_type = AVRCP_CTYPE_NOTIFY;
543     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
544     connection->subunit_id = AVRCP_SUBUNIT_ID;
545     int pos = 0;
546     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
547     pos += 3;
548     connection->cmd_operands[pos++] = AVRCP_PDU_ID_REGISTER_NOTIFICATION;
549     connection->cmd_operands[pos++] = 0;                     // reserved(upper 6) | packet_type -> 0
550     big_endian_store_16(connection->cmd_operands, pos, 5);     // parameter length
551     pos += 2;
552     connection->cmd_operands[pos++] = event_id;
553     big_endian_store_32(connection->cmd_operands, pos, 0);
554     pos += 4;
555     connection->cmd_operands_length = pos;
556     // AVRCP_SPEC_V14.pdf 166
557     // answer page 61
558 }
559 
560 static uint8_t avrcp_cmd_opcode(uint8_t *packet, uint16_t size){
561     uint8_t cmd_opcode_index = 5;
562     if (cmd_opcode_index > size) return AVRCP_CMD_OPCODE_UNDEFINED;
563     return packet[cmd_opcode_index];
564 }
565 
566 static void avrcp_handle_sdp_client_query_result(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
567     if (!sdp_query_context.connection) return;
568     if (sdp_query_context.connection->state != AVCTP_SIGNALING_W4_SDP_QUERY_COMPLETE) return;
569     UNUSED(packet_type);
570     UNUSED(channel);
571     UNUSED(size);
572 
573     des_iterator_t des_list_it;
574     des_iterator_t prot_it;
575     // uint32_t avdtp_remote_uuid    = 0;
576 
577     switch (hci_event_packet_get_type(packet)){
578         case SDP_EVENT_QUERY_ATTRIBUTE_VALUE:
579             // Handle new SDP record
580             if (sdp_event_query_attribute_byte_get_record_id(packet) != record_id) {
581                 record_id = sdp_event_query_attribute_byte_get_record_id(packet);
582                 // log_info("SDP Record: Nr: %d", record_id);
583             }
584 
585             if (sdp_event_query_attribute_byte_get_attribute_length(packet) <= attribute_value_buffer_size) {
586                 attribute_value[sdp_event_query_attribute_byte_get_data_offset(packet)] = sdp_event_query_attribute_byte_get_data(packet);
587 
588                 if ((uint16_t)(sdp_event_query_attribute_byte_get_data_offset(packet)+1) == sdp_event_query_attribute_byte_get_attribute_length(packet)) {
589                     switch(sdp_event_query_attribute_byte_get_attribute_id(packet)) {
590                         case BLUETOOTH_ATTRIBUTE_SERVICE_CLASS_ID_LIST:
591                             if (de_get_element_type(attribute_value) != DE_DES) break;
592                             for (des_iterator_init(&des_list_it, attribute_value); des_iterator_has_more(&des_list_it); des_iterator_next(&des_list_it)) {
593                                 uint8_t * element = des_iterator_get_element(&des_list_it);
594                                 if (de_get_element_type(element) != DE_UUID) continue;
595                                 uint32_t uuid = de_get_uuid32(element);
596                                 switch (uuid){
597                                     case BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_TARGET:
598                                         if (sdp_query_context.avrcp_context->role == AVRCP_TARGET) {
599                                             sdp_query_context.role_supported = 1;
600                                             break;
601                                         }
602                                         break;
603                                     case BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL:
604                                     case BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_CONTROLLER:
605                                         if (sdp_query_context.avrcp_context->role == AVRCP_CONTROLLER) {
606                                             sdp_query_context.role_supported = 1;
607                                             break;
608                                         }
609                                         break;
610                                     default:
611                                         break;
612                                 }
613                             }
614                             break;
615 
616                         case BLUETOOTH_ATTRIBUTE_PROTOCOL_DESCRIPTOR_LIST: {
617                                 // log_info("SDP Attribute: 0x%04x", sdp_event_query_attribute_byte_get_attribute_id(packet));
618                                 for (des_iterator_init(&des_list_it, attribute_value); des_iterator_has_more(&des_list_it); des_iterator_next(&des_list_it)) {
619                                     uint8_t       *des_element;
620                                     uint8_t       *element;
621                                     uint32_t       uuid;
622 
623                                     if (des_iterator_get_type(&des_list_it) != DE_DES) continue;
624 
625                                     des_element = des_iterator_get_element(&des_list_it);
626                                     des_iterator_init(&prot_it, des_element);
627                                     element = des_iterator_get_element(&prot_it);
628 
629                                     if (de_get_element_type(element) != DE_UUID) continue;
630 
631                                     uuid = de_get_uuid32(element);
632                                     switch (uuid){
633                                         case BLUETOOTH_PROTOCOL_L2CAP:
634                                             if (!des_iterator_has_more(&prot_it)) continue;
635                                             des_iterator_next(&prot_it);
636                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_l2cap_psm);
637                                             break;
638                                         case BLUETOOTH_PROTOCOL_AVCTP:
639                                             if (!des_iterator_has_more(&prot_it)) continue;
640                                             des_iterator_next(&prot_it);
641                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_version);
642                                             break;
643                                         default:
644                                             break;
645                                     }
646                                 }
647                             }
648                             break;
649                         case BLUETOOTH_ATTRIBUTE_ADDITIONAL_PROTOCOL_DESCRIPTOR_LISTS: {
650                                 // log_info("SDP Attribute: 0x%04x", sdp_event_query_attribute_byte_get_attribute_id(packet));
651                                 if (de_get_element_type(attribute_value) != DE_DES) break;
652 
653                                 des_iterator_t des_list_0_it;
654                                 uint8_t       *element_0;
655 
656                                 des_iterator_init(&des_list_0_it, attribute_value);
657                                 element_0 = des_iterator_get_element(&des_list_0_it);
658 
659                                 for (des_iterator_init(&des_list_it, element_0); des_iterator_has_more(&des_list_it); des_iterator_next(&des_list_it)) {
660                                     uint8_t       *des_element;
661                                     uint8_t       *element;
662                                     uint32_t       uuid;
663 
664                                     if (des_iterator_get_type(&des_list_it) != DE_DES) continue;
665 
666                                     des_element = des_iterator_get_element(&des_list_it);
667                                     des_iterator_init(&prot_it, des_element);
668                                     element = des_iterator_get_element(&prot_it);
669 
670                                     if (de_get_element_type(element) != DE_UUID) continue;
671 
672                                     uuid = de_get_uuid32(element);
673                                     switch (uuid){
674                                         case BLUETOOTH_PROTOCOL_L2CAP:
675                                             if (!des_iterator_has_more(&prot_it)) continue;
676                                             des_iterator_next(&prot_it);
677                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_browsing_l2cap_psm);
678                                             break;
679                                         case BLUETOOTH_PROTOCOL_AVCTP:
680                                             if (!des_iterator_has_more(&prot_it)) continue;
681                                             des_iterator_next(&prot_it);
682                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_browsing_version);
683                                             break;
684                                         default:
685                                             break;
686                                     }
687                                 }
688                             }
689                             break;
690                         default:
691                             break;
692                     }
693                 }
694             } else {
695                 log_error("SDP attribute value buffer size exceeded: available %d, required %d", attribute_value_buffer_size, sdp_event_query_attribute_byte_get_attribute_length(packet));
696             }
697             break;
698 
699         case SDP_EVENT_QUERY_COMPLETE:
700             log_info("General query done with status %d.", sdp_event_query_complete_get_status(packet));
701             if (!sdp_query_context.role_supported || !sdp_query_context.avrcp_l2cap_psm){
702                 sdp_query_context.connection->state = AVCTP_CONNECTION_IDLE;
703                 avrcp_emit_connection_established(sdp_query_context.avrcp_context->avrcp_callback, sdp_query_context.connection->avrcp_cid, sdp_query_context.connection->remote_addr, SDP_SERVICE_NOT_FOUND);
704                 break;
705             }
706             log_info("AVRCP Control PSM 0x%02x, Browsing PSM 0x%02x", sdp_query_context.avrcp_l2cap_psm, sdp_query_context.avrcp_browsing_l2cap_psm);
707 
708             sdp_query_context.connection->state = AVCTP_CONNECTION_W4_L2CAP_CONNECTED;
709             l2cap_create_channel(sdp_query_context.avrcp_context->packet_handler, sdp_query_context.connection->remote_addr, sdp_query_context.avrcp_l2cap_psm, l2cap_max_mtu(), NULL);
710             break;
711     }
712 }
713 
714 static void avrcp_handle_l2cap_data_packet_for_signaling_connection(avrcp_connection_t * connection, uint8_t *packet, uint16_t size){
715     uint8_t operands[20];
716     uint8_t opcode;
717     int     pos = 3;
718     // uint8_t transport_header = packet[0];
719     // uint8_t transaction_label = transport_header >> 4;
720     // uint8_t packet_type = (transport_header & 0x0F) >> 2;
721     // uint8_t frame_type = (transport_header & 0x03) >> 1;
722     // uint8_t ipid = transport_header & 0x01;
723     // uint8_t byte_value = packet[2];
724     // uint16_t pid = (byte_value << 8) | packet[2];
725 
726     avrcp_command_type_t ctype = (avrcp_command_type_t) packet[pos++];
727     uint8_t byte_value = packet[pos++];
728     avrcp_subunit_type_t subunit_type = (avrcp_subunit_type_t) (byte_value >> 3);
729     avrcp_subunit_type_t subunit_id = (avrcp_subunit_type_t)   (byte_value & 0x07);
730     opcode = packet[pos++];
731 
732     // printf("    Transport header 0x%02x (transaction_label %d, packet_type %d, frame_type %d, ipid %d), pid 0x%4x\n",
733     //     transport_header, transaction_label, packet_type, frame_type, ipid, pid);
734     // // printf_hexdump(packet+pos, size-pos);
735 
736     uint8_t pdu_id;
737     uint16_t param_length;
738     switch (avrcp_cmd_opcode(packet,size)){
739         case AVRCP_CMD_OPCODE_UNIT_INFO:{
740             if (connection->state != AVCTP_W2_RECEIVE_RESPONSE) return;
741             connection->state = AVCTP_CONNECTION_OPENED;
742 
743             // operands:
744             memcpy(operands, packet+pos, 5);
745             uint8_t unit_type = operands[1] >> 3;
746             uint8_t unit = operands[1] & 0x07;
747             uint32_t company_id = operands[2] << 16 | operands[3] << 8 | operands[4];
748             log_info("    UNIT INFO response: ctype 0x%02x (0C), subunit_type 0x%02x (1F), subunit_id 0x%02x (07), opcode 0x%02x (30), unit_type 0x%02x, unit %d, company_id 0x%06x",
749                 ctype, subunit_type, subunit_id, opcode, unit_type, unit, company_id );
750             break;
751         }
752         case AVRCP_CMD_OPCODE_VENDOR_DEPENDENT:
753             if (size - pos < 7) {
754                 log_error("avrcp: wrong packet size");
755                 return;
756             };
757             // operands:
758             memcpy(operands, packet+pos, 7);
759             pos += 7;
760             // uint32_t company_id = operands[0] << 16 | operands[1] << 8 | operands[2];
761             pdu_id = operands[3];
762 
763             if (connection->state != AVCTP_W2_RECEIVE_RESPONSE && pdu_id != AVRCP_PDU_ID_REGISTER_NOTIFICATION){
764                 log_info("AVRCP_CMD_OPCODE_VENDOR_DEPENDENT state %d", connection->state);
765                 return;
766             }
767             connection->state = AVCTP_CONNECTION_OPENED;
768 
769 
770             // uint8_t unit_type = operands[4] >> 3;
771             // uint8_t unit = operands[4] & 0x07;
772             param_length = big_endian_read_16(operands, 5);
773 
774             // printf("    VENDOR DEPENDENT response: ctype 0x%02x (0C), subunit_type 0x%02x (1F), subunit_id 0x%02x (07), opcode 0x%02x (30), unit_type 0x%02x, unit %d, company_id 0x%06x\n",
775             //     ctype, subunit_type, subunit_id, opcode, unit_type, unit, company_id );
776 
777             // if (ctype == AVRCP_CTYPE_RESPONSE_INTERIM) return;
778             log_info("        VENDOR DEPENDENT response: pdu id 0x%02x, param_length %d, status %s", pdu_id, param_length, avrcp_ctype2str(ctype));
779             switch (pdu_id){
780                 case AVRCP_PDU_ID_GetCurrentPlayerApplicationSettingValue:{
781                     uint8_t num_attributes = packet[pos++];
782                     int i;
783                     avrcp_repeat_mode_t  repeat_mode =  AVRCP_REPEAT_MODE_INVALID;
784                     avrcp_shuffle_mode_t shuffle_mode = AVRCP_SHUFFLE_MODE_INVALID;
785                     for (i = 0; i < num_attributes; i++){
786                         uint8_t attribute_id    = packet[pos++];
787                         uint8_t value = packet[pos++];
788                         switch (attribute_id){
789                             case 0x02:
790                                 repeat_mode = (avrcp_repeat_mode_t) value;
791                                 break;
792                             case 0x03:
793                                 shuffle_mode = (avrcp_shuffle_mode_t) value;
794                                 break;
795                             default:
796                                 break;
797                         }
798                     }
799                     avrcp_emit_repeat_and_shuffle_mode(avrcp_callback, connection->avrcp_cid, ctype, repeat_mode, shuffle_mode);
800                     break;
801                 }
802                 case AVRCP_PDU_ID_SetPlayerApplicationSettingValue:{
803                     uint8_t event[6];
804                     int offset = 0;
805                     event[offset++] = HCI_EVENT_AVRCP_META;
806                     event[offset++] = sizeof(event) - 2;
807                     event[offset++] = AVRCP_SUBEVENT_PLAYER_APPLICATION_VALUE_RESPONSE;
808                     little_endian_store_16(event, offset, connection->avrcp_cid);
809                     offset += 2;
810                     event[offset++] = ctype;
811                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
812                     break;
813                 }
814                 case AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME:{
815                     uint8_t event[7];
816                     int offset = 0;
817                     event[offset++] = HCI_EVENT_AVRCP_META;
818                     event[offset++] = sizeof(event) - 2;
819                     event[offset++] = AVRCP_SUBEVENT_SET_ABSOLUTE_VOLUME_RESPONSE;
820                     little_endian_store_16(event, offset, connection->avrcp_cid);
821                     offset += 2;
822                     event[offset++] = ctype;
823                     event[offset++] = packet[pos++];
824                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
825                     break;
826                 }
827                 case AVRCP_PDU_ID_GET_CAPABILITIES:{
828                     avrcp_capability_id_t capability_id = (avrcp_capability_id_t) packet[pos++];
829                     uint8_t capability_count = packet[pos++];
830                     int i;
831                     switch (capability_id){
832                         case AVRCP_CAPABILITY_ID_COMPANY:
833                             // log_info("Supported companies %d: ", capability_count);
834                             for (i = 0; i < capability_count; i++){
835                                 uint32_t company_id = big_endian_read_24(packet, pos);
836                                 pos += 3;
837                                 log_info("  0x%06x, ", company_id);
838                             }
839                             break;
840                         case AVRCP_CAPABILITY_ID_EVENT:
841                             // log_info("Supported events %d: ", capability_count);
842                             for (i = 0; i < capability_count; i++){
843                                 uint8_t event_id = packet[pos++];
844                                 log_info("  0x%02x %s", event_id, avrcp_event2str(event_id));
845                             }
846                             break;
847                     }
848                     break;
849                 }
850                 case AVRCP_PDU_ID_GET_PLAY_STATUS:{
851                     uint32_t song_length = big_endian_read_32(packet, pos);
852                     pos += 4;
853                     uint32_t song_position = big_endian_read_32(packet, pos);
854                     pos += 4;
855                     uint8_t play_status = packet[pos];
856                     // log_info("        GET_PLAY_STATUS length 0x%04X, position 0x%04X, status %s", song_length, song_position, avrcp_play_status2str(play_status));
857 
858                     uint8_t event[15];
859                     int offset = 0;
860                     event[offset++] = HCI_EVENT_AVRCP_META;
861                     event[offset++] = sizeof(event) - 2;
862                     event[offset++] = AVRCP_SUBEVENT_PLAY_STATUS;
863                     little_endian_store_16(event, offset, connection->avrcp_cid);
864                     offset += 2;
865                     event[offset++] = ctype;
866                     little_endian_store_32(event, offset, song_length);
867                     offset += 4;
868                     little_endian_store_32(event, offset, song_position);
869                     offset += 4;
870                     event[offset++] = play_status;
871                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
872                     break;
873                 }
874                 case AVRCP_PDU_ID_REGISTER_NOTIFICATION:{
875                     avrcp_notification_event_id_t  event_id = (avrcp_notification_event_id_t) packet[pos++];
876                     uint16_t event_mask = (1 << event_id);
877                     uint16_t reset_event_mask = ~event_mask;
878                     switch (ctype){
879                         case AVRCP_CTYPE_RESPONSE_INTERIM:
880                             // register as enabled
881                             connection->notifications_enabled |= event_mask;
882                             // printf("INTERIM notifications_enabled 0x%2x, notifications_to_register 0x%2x\n", connection->notifications_enabled,  connection->notifications_to_register);
883                             break;
884                         case AVRCP_CTYPE_RESPONSE_CHANGED_STABLE:
885                             // received change, event is considered deregistered
886                             // we are re-enabling it automatically, if it is not
887                             // explicitly disabled
888                             connection->notifications_enabled &= reset_event_mask;
889                             if (! (connection->notifications_to_deregister & event_mask)){
890                                 avrcp_register_notification(connection, event_id);
891                                 // printf("CHANGED_STABLE notifications_enabled 0x%2x, notifications_to_register 0x%2x\n", connection->notifications_enabled,  connection->notifications_to_register);
892                             } else {
893                                 connection->notifications_to_deregister &= reset_event_mask;
894                             }
895                             break;
896                         default:
897                             connection->notifications_to_register &= reset_event_mask;
898                             connection->notifications_enabled &= reset_event_mask;
899                             connection->notifications_to_deregister &= reset_event_mask;
900                             break;
901                     }
902 
903                     switch (event_id){
904                         case AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED:{
905                             uint8_t event[7];
906                             int offset = 0;
907                             event[offset++] = HCI_EVENT_AVRCP_META;
908                             event[offset++] = sizeof(event) - 2;
909                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_PLAYBACK_STATUS_CHANGED;
910                             little_endian_store_16(event, offset, connection->avrcp_cid);
911                             offset += 2;
912                             event[offset++] = ctype;
913                             event[offset++] = packet[pos];
914                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
915                             break;
916                         }
917                         case AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED:{
918                             uint8_t event[6];
919                             int offset = 0;
920                             event[offset++] = HCI_EVENT_AVRCP_META;
921                             event[offset++] = sizeof(event) - 2;
922                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_TRACK_CHANGED;
923                             little_endian_store_16(event, offset, connection->avrcp_cid);
924                             offset += 2;
925                             event[offset++] = ctype;
926                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
927                             break;
928                         }
929                         case AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED:{
930                             uint8_t event[6];
931                             int offset = 0;
932                             event[offset++] = HCI_EVENT_AVRCP_META;
933                             event[offset++] = sizeof(event) - 2;
934                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_NOW_PLAYING_CONTENT_CHANGED;
935                             little_endian_store_16(event, offset, connection->avrcp_cid);
936                             offset += 2;
937                             event[offset++] = ctype;
938                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
939                             break;
940                         }
941                         case AVRCP_NOTIFICATION_EVENT_AVAILABLE_PLAYERS_CHANGED:{
942                             uint8_t event[6];
943                             int offset = 0;
944                             event[offset++] = HCI_EVENT_AVRCP_META;
945                             event[offset++] = sizeof(event) - 2;
946                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_AVAILABLE_PLAYERS_CHANGED;
947                             little_endian_store_16(event, offset, connection->avrcp_cid);
948                             offset += 2;
949                             event[offset++] = ctype;
950                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
951                             break;
952                         }
953                         case AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED:{
954                             uint8_t event[7];
955                             int offset = 0;
956                             event[offset++] = HCI_EVENT_AVRCP_META;
957                             event[offset++] = sizeof(event) - 2;
958                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_VOLUME_CHANGED;
959                             little_endian_store_16(event, offset, connection->avrcp_cid);
960                             offset += 2;
961                             event[offset++] = ctype;
962                             event[offset++] = packet[pos++] & 0x7F;
963                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
964                             break;
965                         }
966                         // case AVRCP_NOTIFICATION_EVENT_PLAYER_APPLICATION_SETTING_CHANGED:{
967                         //     uint8_t num_PlayerApplicationSettingAttributes = packet[pos++];
968                         //     int i;
969                         //     for (i = 0; i < num_PlayerApplicationSettingAttributes; i++){
970                         //         uint8_t PlayerApplicationSetting_AttributeID = packet[pos++];
971                         //         uint8_t PlayerApplicationSettingValueID = packet[pos++];
972                         //     }
973                         //     break;
974                         // }
975                         // case AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED:
976                         //     uint16_t player_id = big_endian_read_16(packet, pos);
977                         //     pos += 2;
978                         //     uint16_t uid_counter = big_endian_read_16(packet, pos);
979                         //     pos += 2;
980                         //     break;
981                         // case AVRCP_NOTIFICATION_EVENT_UIDS_CHANGED:
982                         //     uint16_t uid_counter = big_endian_read_16(packet, pos);
983                         //     pos += 2;
984                         //     break;
985                         default:
986                             log_info("avrcp: not implemented");
987                             break;
988                     }
989                     if (connection->notifications_to_register != 0){
990                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
991                     }
992                     break;
993                 }
994 
995                 case AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES:{
996                     uint8_t num_attributes = packet[pos++];
997                     int i;
998                     struct item {
999                         uint16_t len;
1000                         uint8_t  * value;
1001                     } items[AVRCP_MEDIA_ATTR_COUNT];
1002                     memset(items, 0, sizeof(items));
1003 
1004                     uint16_t string_attributes_len = 0;
1005                     uint8_t  num_string_attributes = 0;
1006                     uint16_t total_event_payload_for_string_attributes = HCI_EVENT_PAYLOAD_SIZE-2;
1007                     uint16_t max_string_attribute_value_len = 0;
1008                     if (ctype == AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE || ctype == AVRCP_CTYPE_RESPONSE_CHANGED_STABLE){
1009                         for (i = 0; i < num_attributes; i++){
1010                             avrcp_media_attribute_id_t attr_id = (avrcp_media_attribute_id_t) big_endian_read_32(packet, pos);
1011                             pos += 4;
1012                             // uint16_t character_set = big_endian_read_16(packet, pos);
1013                             pos += 2;
1014                             uint16_t attr_value_length = big_endian_read_16(packet, pos);
1015                             pos += 2;
1016 
1017                             // debug - to remove later
1018                             uint8_t  value[100];
1019                             uint16_t value_len = sizeof(value) <= attr_value_length? sizeof(value) - 1 : attr_value_length;
1020                             memcpy(value, packet+pos, value_len);
1021                             value[value_len] = 0;
1022                             // printf("Now Playing Info %s: %s \n", attribute2str(attr_id), value);
1023                             // end debug
1024 
1025                             if ((attr_id >= 1) || (attr_id <= AVRCP_MEDIA_ATTR_COUNT)) {
1026                                 items[attr_id-1].len = attr_value_length;
1027                                 items[attr_id-1].value = &packet[pos];
1028                                 switch (attr_id){
1029                                     case AVRCP_MEDIA_ATTR_TITLE:
1030                                     case AVRCP_MEDIA_ATTR_ARTIST:
1031                                     case AVRCP_MEDIA_ATTR_ALBUM:
1032                                     case AVRCP_MEDIA_ATTR_GENRE:
1033                                         num_string_attributes++;
1034                                         string_attributes_len += attr_value_length;
1035                                         if (max_string_attribute_value_len < attr_value_length){
1036                                             max_string_attribute_value_len = attr_value_length;
1037                                         }
1038                                         break;
1039                                     default:
1040                                         break;
1041                                 }
1042                             }
1043                             pos += attr_value_length;
1044                         }
1045                     }
1046 
1047                     // subtract space for fixed fields
1048                     total_event_payload_for_string_attributes -= 14 + 4;    // 4 for '\0'
1049 
1050                     // @TODO optimize space by repeatedly decreasing max_string_attribute_value_len until it fits into buffer instead of crude divion
1051                     uint16_t max_value_len = total_event_payload_for_string_attributes > string_attributes_len? max_string_attribute_value_len : total_event_payload_for_string_attributes/(string_attributes_len+1) - 1;
1052                     // printf("num_string_attributes %d, string_attributes_len %d, total_event_payload_for_string_attributes %d, max_value_len %d \n", num_string_attributes, string_attributes_len, total_event_payload_for_string_attributes, max_value_len);
1053 
1054                     const uint8_t attribute_order[] = {
1055                         AVRCP_MEDIA_ATTR_TRACK,
1056                         AVRCP_MEDIA_ATTR_TOTAL_TRACKS,
1057                         AVRCP_MEDIA_ATTR_SONG_LENGTH,
1058                         AVRCP_MEDIA_ATTR_TITLE,
1059                         AVRCP_MEDIA_ATTR_ARTIST,
1060                         AVRCP_MEDIA_ATTR_ALBUM,
1061                         AVRCP_MEDIA_ATTR_GENRE
1062                     };
1063 
1064                     uint8_t event[HCI_EVENT_BUFFER_SIZE];
1065                     event[0] = HCI_EVENT_AVRCP_META;
1066                     pos = 2;
1067                     event[pos++] = AVRCP_SUBEVENT_NOW_PLAYING_INFO;
1068                     little_endian_store_16(event, pos, connection->avrcp_cid);
1069                     pos += 2;
1070                     event[pos++] = ctype;
1071                     for (i = 0; i < sizeof(attribute_order); i++){
1072                         avrcp_media_attribute_id_t attr_id = (avrcp_media_attribute_id_t) attribute_order[i];
1073                         uint16_t value_len = 0;
1074                         switch (attr_id){
1075                             case AVRCP_MEDIA_ATTR_TITLE:
1076                             case AVRCP_MEDIA_ATTR_ARTIST:
1077                             case AVRCP_MEDIA_ATTR_ALBUM:
1078                             case AVRCP_MEDIA_ATTR_GENRE:
1079                                 if (items[attr_id-1].value){
1080                                     value_len = items[attr_id-1].len <= max_value_len ? items[attr_id-1].len : max_value_len;
1081                                 }
1082                                 event[pos++] = value_len + 1;
1083                                 if (value_len){
1084                                     memcpy(event+pos, items[attr_id-1].value, value_len);
1085                                     pos += value_len;
1086                                 }
1087                                 event[pos++] = 0;
1088                                 break;
1089                             case AVRCP_MEDIA_ATTR_SONG_LENGTH:
1090                                 if (items[attr_id-1].value){
1091                                     little_endian_store_32(event, pos, btstack_atoi((char *)items[attr_id-1].value));
1092                                 } else {
1093                                     little_endian_store_32(event, pos, 0);
1094                                 }
1095                                 pos += 4;
1096                                 break;
1097                             case AVRCP_MEDIA_ATTR_TRACK:
1098                             case AVRCP_MEDIA_ATTR_TOTAL_TRACKS:
1099                                 if (items[attr_id-1].value){
1100                                     event[pos++] = btstack_atoi((char *)items[attr_id-1].value);
1101                                 } else {
1102                                     event[pos++] = 0;
1103                                 }
1104                                 break;
1105                         }
1106                     }
1107                     event[1] = pos - 2;
1108                     // printf_hexdump(event, pos);
1109                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, pos);
1110                     break;
1111                 }
1112                 default:
1113                     break;
1114             }
1115             break;
1116         case AVRCP_CMD_OPCODE_PASS_THROUGH:{
1117             // 0x80 | connection->cmd_operands[0]
1118             uint8_t operation_id = packet[pos++];
1119             switch (connection->state){
1120                 case AVCTP_W2_RECEIVE_PRESS_RESPONSE:
1121                     if (connection->continuous_fast_forward_cmd){
1122                         connection->state = AVCTP_W4_STOP;
1123                     } else {
1124                         connection->state = AVCTP_W2_SEND_RELEASE_COMMAND;
1125                     }
1126                     break;
1127                 case AVCTP_W2_RECEIVE_RESPONSE:
1128                     connection->state = AVCTP_CONNECTION_OPENED;
1129                     break;
1130                 default:
1131                     // check for notifications? move state transition down
1132                     // log_info("AVRCP_CMD_OPCODE_PASS_THROUGH state %d\n", connection->state);
1133                     break;
1134             }
1135             if (connection->state == AVCTP_W4_STOP){
1136                 avrcp_emit_operation_status(avrcp_callback, AVRCP_SUBEVENT_OPERATION_START, connection->avrcp_cid, ctype, operation_id);
1137             }
1138             if (connection->state == AVCTP_CONNECTION_OPENED) {
1139                 // RELEASE response
1140                 operation_id = operation_id & 0x7F;
1141                 avrcp_emit_operation_status(avrcp_callback, AVRCP_SUBEVENT_OPERATION_COMPLETE, connection->avrcp_cid, ctype, operation_id);
1142             }
1143             if (connection->state == AVCTP_W2_SEND_RELEASE_COMMAND){
1144                 // PRESS response
1145                 request_pass_through_release_control_cmd(connection);
1146             }
1147             break;
1148         }
1149         default:
1150             break;
1151     }
1152 }
1153 
1154 static void avrcp_handle_can_send_now(avrcp_connection_t * connection){
1155     int i;
1156     switch (connection->state){
1157         case AVCTP_W2_SEND_PRESS_COMMAND:
1158             connection->state = AVCTP_W2_RECEIVE_PRESS_RESPONSE;
1159             avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
1160             break;
1161         case AVCTP_W2_SEND_COMMAND:
1162         case AVCTP_W2_SEND_RELEASE_COMMAND:
1163             connection->state = AVCTP_W2_RECEIVE_RESPONSE;
1164             avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
1165             break;
1166         case AVCTP_CONNECTION_OPENED:
1167             if (connection->notifications_to_register != 0){
1168                 for (i = 1; i <= AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED; i++){
1169                     if (connection->notifications_to_register & (1<<i)){
1170                         connection->notifications_to_register &= ~ (1 << i);
1171                         avrcp_prepare_notification(connection, (avrcp_notification_event_id_t) i);
1172                         connection->state = AVCTP_W2_RECEIVE_RESPONSE;
1173                         avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
1174                         return;
1175                     }
1176                 }
1177             }
1178             return;
1179         default:
1180             return;
1181     }
1182 }
1183 
1184 static avrcp_connection_t * avrcp_create_connection(bd_addr_t remote_addr, avrcp_context_t * context){
1185     avrcp_connection_t * connection = btstack_memory_avrcp_connection_get();
1186     memset(connection, 0, sizeof(avrcp_connection_t));
1187     connection->state = AVCTP_CONNECTION_IDLE;
1188     connection->transaction_label = 0xFF;
1189     memcpy(connection->remote_addr, remote_addr, 6);
1190     btstack_linked_list_add(&context->connections, (btstack_linked_item_t *) connection);
1191     return connection;
1192 }
1193 
1194 static void packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size, avrcp_context_t * context){
1195     bd_addr_t event_addr;
1196     uint16_t local_cid;
1197     avrcp_connection_t * connection = NULL;
1198 
1199     switch (packet_type) {
1200         case L2CAP_DATA_PACKET:
1201             connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, context);
1202             if (!connection) break;
1203             avrcp_handle_l2cap_data_packet_for_signaling_connection(connection, packet, size);
1204             break;
1205 
1206         case HCI_EVENT_PACKET:
1207             switch (hci_event_packet_get_type(packet)) {
1208                 case L2CAP_EVENT_INCOMING_CONNECTION:
1209                     l2cap_event_incoming_connection_get_address(packet, event_addr);
1210                     local_cid = l2cap_event_incoming_connection_get_local_cid(packet);
1211                     connection = avrcp_create_connection(event_addr, context);
1212                     if (!connection) {
1213                         log_error("Failed to alloc connection structure");
1214                         l2cap_decline_connection(local_cid);
1215                         break;
1216                     }
1217                     connection->state = AVCTP_CONNECTION_W4_L2CAP_CONNECTED;
1218                     connection->l2cap_signaling_cid = local_cid;
1219                     l2cap_accept_connection(local_cid);
1220                     break;
1221 
1222                 case L2CAP_EVENT_CHANNEL_OPENED:
1223                     l2cap_event_channel_opened_get_address(packet, event_addr);
1224 
1225                     connection = get_avrcp_connection_for_bd_addr(event_addr, context);
1226                     local_cid  = l2cap_event_channel_opened_get_local_cid(packet);
1227 
1228                     if (!connection){
1229                         // incoming connection
1230                         connection = avrcp_create_connection(event_addr, context);
1231                         if (!connection) {
1232                             log_error("Failed to alloc connection structure");
1233                             l2cap_disconnect(local_cid, 0); // reason isn't used
1234                             break;
1235                         }
1236                         connection->l2cap_signaling_cid = local_cid;
1237                         connection->avrcp_cid = avrcp_cid_counter++;
1238                     }
1239 
1240                     if (l2cap_event_channel_opened_get_status(packet)){
1241                         log_info("L2CAP connection to connection %s failed. status code 0x%02x",
1242                             bd_addr_to_str(event_addr), l2cap_event_channel_opened_get_status(packet));
1243                         if (connection->state == AVCTP_CONNECTION_W4_L2CAP_CONNECTED && connection->l2cap_signaling_cid == local_cid){
1244                             avrcp_emit_connection_established(avrcp_callback, connection->avrcp_cid, event_addr, l2cap_event_channel_opened_get_status(packet));
1245                         }
1246                         // free connection
1247                         btstack_linked_list_remove(&context->connections, (btstack_linked_item_t*) connection);
1248                         btstack_memory_avrcp_connection_free(connection);
1249                         break;
1250                     }
1251                     connection->l2cap_signaling_cid = local_cid;
1252                     log_info("L2CAP_EVENT_CHANNEL_OPENED avrcp_cid 0x%02x, l2cap_signaling_cid 0x%02x",connection->avrcp_cid, connection->l2cap_signaling_cid);
1253                     connection->state = AVCTP_CONNECTION_OPENED;
1254                     avrcp_emit_connection_established(avrcp_callback, connection->avrcp_cid, event_addr, ERROR_CODE_SUCCESS);
1255 
1256                     // hack
1257                     // l2cap_create_channel(avrcp_controller_context.packet_handler, connection->remote_addr, 0x001b, l2cap_max_mtu(), NULL);
1258                     break;
1259 
1260                 case L2CAP_EVENT_CAN_SEND_NOW:
1261                     connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, context);
1262                     if (!connection) break;
1263                     avrcp_handle_can_send_now(connection);
1264                     break;
1265 
1266                 case L2CAP_EVENT_CHANNEL_CLOSED:
1267                     // data: event (8), len(8), channel (16)
1268                     local_cid = l2cap_event_channel_closed_get_local_cid(packet);
1269                     connection = get_avrcp_connection_for_l2cap_signaling_cid(local_cid, context);
1270                     if (connection){
1271                         avrcp_emit_connection_closed(avrcp_callback, connection->avrcp_cid);
1272                         // free connection
1273                         btstack_linked_list_remove(&context->connections, (btstack_linked_item_t*) connection);
1274                         btstack_memory_avrcp_connection_free(connection);
1275                         break;
1276                     }
1277                     break;
1278                 default:
1279                     break;
1280             }
1281             break;
1282         default:
1283             break;
1284     }
1285 }
1286 
1287 static void avrcp_controller_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
1288     packet_handler(packet_type, channel, packet, size, &avrcp_controller_context);
1289 }
1290 
1291 void avrcp_controller_init(void){
1292     avrcp_controller_context.role = AVRCP_CONTROLLER;
1293     avrcp_controller_context.connections = NULL;
1294     avrcp_controller_context.avrcp_callback = avrcp_callback;
1295     avrcp_controller_context.packet_handler = avrcp_controller_packet_handler;
1296     l2cap_register_service(&avrcp_controller_packet_handler, BLUETOOTH_PROTOCOL_AVCTP, 0xffff, LEVEL_0);
1297 }
1298 
1299 void avrcp_register_packet_handler(btstack_packet_handler_t callback){
1300     if (callback == NULL){
1301         log_error("avrcp_register_packet_handler called with NULL callback");
1302         return;
1303     }
1304     avrcp_callback = callback;
1305     avrcp_controller_context.avrcp_callback = avrcp_callback;
1306 }
1307 
1308 uint8_t avrcp_connect(bd_addr_t bd_addr, avrcp_context_t * context, uint16_t * avrcp_cid){
1309     avrcp_connection_t * connection = get_avrcp_connection_for_bd_addr(bd_addr, context);
1310     if (connection){
1311         return ERROR_CODE_COMMAND_DISALLOWED;
1312     }
1313 
1314     connection = avrcp_create_connection(bd_addr, context);
1315     if (!connection){
1316         log_error("avrcp: could not allocate connection struct.");
1317         return BTSTACK_MEMORY_ALLOC_FAILED;
1318     }
1319 
1320     if (!avrcp_cid) return L2CAP_LOCAL_CID_DOES_NOT_EXIST;
1321 
1322     *avrcp_cid = avrcp_cid_counter++;
1323     connection->avrcp_cid = *avrcp_cid;
1324 
1325     connection->state = AVCTP_SIGNALING_W4_SDP_QUERY_COMPLETE;
1326     sdp_query_context.avrcp_context = context;
1327     sdp_query_context.avrcp_l2cap_psm = 0;
1328     sdp_query_context.avrcp_version = 0;
1329     sdp_query_context.connection = connection;
1330 
1331     sdp_client_query_uuid16(&avrcp_handle_sdp_client_query_result, bd_addr, BLUETOOTH_PROTOCOL_AVCTP);
1332     return ERROR_CODE_SUCCESS;
1333 }
1334 
1335 uint8_t avrcp_controller_connect(bd_addr_t bd_addr, uint16_t * avrcp_cid){
1336     return avrcp_connect(bd_addr, &avrcp_controller_context, avrcp_cid);
1337 }
1338 
1339 uint8_t avrcp_unit_info(uint16_t avrcp_cid){
1340     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1341     if (!connection){
1342         log_error("avrcp_unit_info: could not find a connection.");
1343         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1344     }
1345     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1346     connection->state = AVCTP_W2_SEND_COMMAND;
1347 
1348     connection->transaction_label++;
1349     connection->command_opcode = AVRCP_CMD_OPCODE_UNIT_INFO;
1350     connection->command_type = AVRCP_CTYPE_STATUS;
1351     connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
1352     connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
1353     memset(connection->cmd_operands, 0xFF, connection->cmd_operands_length);
1354     connection->cmd_operands_length = 5;
1355     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1356     return ERROR_CODE_SUCCESS;
1357 }
1358 
1359 static uint8_t avrcp_get_capabilities(uint16_t avrcp_cid, uint8_t capability_id){
1360     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1361     if (!connection){
1362         log_error("avrcp_get_capabilities: could not find a connection.");
1363         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1364     }
1365     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1366     connection->state = AVCTP_W2_SEND_COMMAND;
1367 
1368     connection->transaction_label++;
1369     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1370     connection->command_type = AVRCP_CTYPE_STATUS;
1371     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1372     connection->subunit_id = AVRCP_SUBUNIT_ID;
1373     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
1374     connection->cmd_operands[3] = AVRCP_PDU_ID_GET_CAPABILITIES; // PDU ID
1375     connection->cmd_operands[4] = 0;
1376     big_endian_store_16(connection->cmd_operands, 5, 1); // parameter length
1377     connection->cmd_operands[7] = capability_id;                  // capability ID
1378     connection->cmd_operands_length = 8;
1379     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1380     return ERROR_CODE_SUCCESS;
1381 }
1382 
1383 uint8_t avrcp_get_supported_company_ids(uint16_t avrcp_cid){
1384     return avrcp_get_capabilities(avrcp_cid, AVRCP_CAPABILITY_ID_COMPANY);
1385 }
1386 
1387 uint8_t avrcp_get_supported_events(uint16_t avrcp_cid){
1388     return avrcp_get_capabilities(avrcp_cid, AVRCP_CAPABILITY_ID_EVENT);
1389 }
1390 
1391 
1392 uint8_t avrcp_play(uint16_t avrcp_cid){
1393     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_PLAY, 0);
1394 }
1395 
1396 uint8_t avrcp_stop(uint16_t avrcp_cid){
1397     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_STOP, 0);
1398 }
1399 
1400 uint8_t avrcp_pause(uint16_t avrcp_cid){
1401     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_PAUSE, 0);
1402 }
1403 
1404 uint8_t avrcp_forward(uint16_t avrcp_cid){
1405     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FORWARD, 0);
1406 }
1407 
1408 uint8_t avrcp_backward(uint16_t avrcp_cid){
1409     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_BACKWARD, 0);
1410 }
1411 
1412 uint8_t avrcp_start_rewind(uint16_t avrcp_cid){
1413     return request_continuous_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_REWIND, 0);
1414 }
1415 
1416 uint8_t avrcp_volume_up(uint16_t avrcp_cid){
1417     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_VOLUME_UP, 0);
1418 }
1419 
1420 uint8_t avrcp_volume_down(uint16_t avrcp_cid){
1421     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_VOLUME_DOWN, 0);
1422 }
1423 
1424 uint8_t avrcp_mute(uint16_t avrcp_cid){
1425     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_MUTE, 0);
1426 }
1427 
1428 uint8_t avrcp_skip(uint16_t avrcp_cid){
1429     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_SKIP, 0);
1430 }
1431 
1432 uint8_t avrcp_stop_rewind(uint16_t avrcp_cid){
1433     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1434     if (!connection){
1435         log_error("avrcp_stop_rewind: could not find a connection.");
1436         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1437     }
1438     if (connection->state != AVCTP_W4_STOP) return ERROR_CODE_COMMAND_DISALLOWED;
1439     return request_pass_through_release_control_cmd(connection);
1440 }
1441 
1442 uint8_t avrcp_start_fast_forward(uint16_t avrcp_cid){
1443     return request_continuous_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FAST_FORWARD, 0);
1444 }
1445 
1446 uint8_t avrcp_fast_forward(uint16_t avrcp_cid){
1447     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FAST_FORWARD, 0);
1448 }
1449 
1450 uint8_t avrcp_rewind(uint16_t avrcp_cid){
1451     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_REWIND, 0);
1452 }
1453 
1454 
1455 uint8_t avrcp_stop_fast_forward(uint16_t avrcp_cid){
1456     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1457     if (!connection){
1458         log_error("avrcp_stop_fast_forward: could not find a connection.");
1459         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1460     }
1461     if (connection->state != AVCTP_W4_STOP) return ERROR_CODE_COMMAND_DISALLOWED;
1462     return request_pass_through_release_control_cmd(connection);
1463 }
1464 
1465 uint8_t avrcp_get_play_status(uint16_t avrcp_cid){
1466     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1467     if (!connection){
1468         log_error("avrcp_get_play_status: could not find a connection.");
1469         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1470     }
1471     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1472     connection->state = AVCTP_W2_SEND_COMMAND;
1473     connection->transaction_label++;
1474     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1475     connection->command_type = AVRCP_CTYPE_STATUS;
1476     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1477     connection->subunit_id = AVRCP_SUBUNIT_ID;
1478     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
1479     connection->cmd_operands[3] = AVRCP_PDU_ID_GET_PLAY_STATUS;
1480     connection->cmd_operands[4] = 0;                     // reserved(upper 6) | packet_type -> 0
1481     big_endian_store_16(connection->cmd_operands, 5, 0); // parameter length
1482     connection->cmd_operands_length = 7;
1483     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1484     return ERROR_CODE_SUCCESS;
1485 }
1486 
1487 uint8_t avrcp_enable_notification(uint16_t avrcp_cid, avrcp_notification_event_id_t event_id){
1488     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1489     if (!connection){
1490         log_error("avrcp_get_play_status: could not find a connection.");
1491         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1492     }
1493     avrcp_register_notification(connection, event_id);
1494     return ERROR_CODE_SUCCESS;
1495 }
1496 
1497 uint8_t avrcp_disable_notification(uint16_t avrcp_cid, avrcp_notification_event_id_t event_id){
1498     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1499     if (!connection){
1500         log_error("avrcp_get_play_status: could not find a connection.");
1501         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1502     }
1503     connection->notifications_to_deregister |= (1 << event_id);
1504     return ERROR_CODE_SUCCESS;
1505 }
1506 
1507 uint8_t avrcp_get_now_playing_info(uint16_t avrcp_cid){
1508     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1509     if (!connection){
1510         log_error("avrcp_get_capabilities: could not find a connection.");
1511         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1512     }
1513     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1514     connection->state = AVCTP_W2_SEND_COMMAND;
1515 
1516     connection->transaction_label++;
1517     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1518     connection->command_type = AVRCP_CTYPE_STATUS;
1519     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1520     connection->subunit_id = AVRCP_SUBUNIT_ID;
1521     int pos = 0;
1522     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
1523     pos += 3;
1524     connection->cmd_operands[pos++] = AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES; // PDU ID
1525     connection->cmd_operands[pos++] = 0;
1526 
1527     // Parameter Length
1528     big_endian_store_16(connection->cmd_operands, pos, 9);
1529     pos += 2;
1530 
1531     // write 8 bytes value
1532     memset(connection->cmd_operands + pos, 0, 8); // identifier: PLAYING
1533     pos += 8;
1534 
1535     connection->cmd_operands[pos++] = 0; // attribute count, if 0 get all attributes
1536     // every attribute is 4 bytes long
1537 
1538     connection->cmd_operands_length = pos;
1539     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1540     return ERROR_CODE_SUCCESS;
1541 }
1542 
1543 uint8_t avrcp_set_absolute_volume(uint16_t avrcp_cid, uint8_t volume){
1544      avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1545     if (!connection){
1546         log_error("avrcp_get_capabilities: could not find a connection.");
1547         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1548     }
1549     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1550     connection->state = AVCTP_W2_SEND_COMMAND;
1551 
1552     connection->transaction_label++;
1553     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1554     connection->command_type = AVRCP_CTYPE_CONTROL;
1555     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1556     connection->subunit_id = AVRCP_SUBUNIT_ID;
1557     int pos = 0;
1558     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
1559     pos += 3;
1560     connection->cmd_operands[pos++] = AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME; // PDU ID
1561     connection->cmd_operands[pos++] = 0;
1562 
1563     // Parameter Length
1564     big_endian_store_16(connection->cmd_operands, pos, 1);
1565     pos += 2;
1566     connection->cmd_operands[pos++] = volume;
1567 
1568     connection->cmd_operands_length = pos;
1569     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1570     return ERROR_CODE_SUCCESS;
1571 }
1572 
1573 uint8_t avrcp_query_shuffle_and_repeat_modes(uint16_t avrcp_cid){
1574     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1575     if (!connection){
1576         log_error("avrcp_get_capabilities: could not find a connection.");
1577         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1578     }
1579     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1580     connection->state = AVCTP_W2_SEND_COMMAND;
1581 
1582     connection->transaction_label++;
1583     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1584     connection->command_type = AVRCP_CTYPE_STATUS;
1585     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1586     connection->subunit_id = AVRCP_SUBUNIT_ID;
1587     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
1588     connection->cmd_operands[3] = AVRCP_PDU_ID_GetCurrentPlayerApplicationSettingValue; // PDU ID
1589     connection->cmd_operands[4] = 0;
1590     big_endian_store_16(connection->cmd_operands, 5, 5); // parameter length
1591     connection->cmd_operands[7] = 4;                     // NumPlayerApplicationSettingAttributeID
1592     // PlayerApplicationSettingAttributeID1 AVRCP Spec, Appendix F, 133
1593     connection->cmd_operands[8]  = 0x01;    // equalizer  (1-OFF, 2-ON)
1594     connection->cmd_operands[9]  = 0x02;    // repeat     (1-off, 2-single track, 3-all tracks, 4-group repeat)
1595     connection->cmd_operands[10] = 0x03;    // shuffle    (1-off, 2-all tracks, 3-group shuffle)
1596     connection->cmd_operands[11] = 0x04;    // scan       (1-off, 2-all tracks, 3-group scan)
1597     connection->cmd_operands_length = 12;
1598     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1599     return ERROR_CODE_SUCCESS;
1600 }
1601 
1602 static uint8_t avrcp_set_current_player_application_setting_value(uint16_t avrcp_cid, uint8_t attr_id, uint8_t attr_value){
1603     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1604     if (!connection){
1605         log_error("avrcp_get_capabilities: could not find a connection.");
1606         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1607     }
1608     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1609     connection->state = AVCTP_W2_SEND_COMMAND;
1610 
1611     connection->transaction_label++;
1612     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1613     connection->command_type = AVRCP_CTYPE_CONTROL;
1614     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1615     connection->subunit_id = AVRCP_SUBUNIT_ID;
1616     int pos = 0;
1617     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
1618     pos += 3;
1619     connection->cmd_operands[pos++] = AVRCP_PDU_ID_SetPlayerApplicationSettingValue; // PDU ID
1620     connection->cmd_operands[pos++] = 0;
1621     // Parameter Length
1622     big_endian_store_16(connection->cmd_operands, pos, 3);
1623     pos += 2;
1624     connection->cmd_operands[pos++] = 2;
1625     connection->cmd_operands_length = pos;
1626     connection->cmd_operands[pos++]  = attr_id;
1627     connection->cmd_operands[pos++]  = attr_value;
1628     connection->cmd_operands_length = pos;
1629     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1630     return ERROR_CODE_SUCCESS;
1631 }
1632 
1633 uint8_t avrcp_set_shuffle_mode(uint16_t avrcp_cid, avrcp_shuffle_mode_t mode){
1634     if (mode < AVRCP_SHUFFLE_MODE_OFF || mode > AVRCP_SHUFFLE_MODE_GROUP) return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
1635     return avrcp_set_current_player_application_setting_value(avrcp_cid, 0x03, mode);
1636 }
1637 
1638 uint8_t avrcp_set_repeat_mode(uint16_t avrcp_cid, avrcp_repeat_mode_t mode){
1639     if (mode < AVRCP_REPEAT_MODE_OFF || mode > AVRCP_REPEAT_MODE_GROUP) return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
1640     return avrcp_set_current_player_application_setting_value(avrcp_cid, 0x02, mode);
1641 }
1642 
1643 uint8_t avrcp_disconnect(uint16_t avrcp_cid){
1644     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1645     if (!connection){
1646         log_error("avrcp_get_capabilities: could not find a connection.");
1647         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1648     }
1649     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1650     l2cap_disconnect(connection->l2cap_signaling_cid, 0);
1651     return ERROR_CODE_SUCCESS;
1652 }