xref: /btstack/src/classic/avrcp_target.c (revision 873b8e568a06e91bdee3ef31830b8b0519d8f1bd)
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_target.c"
39 
40 #include <stdint.h>
41 #include <stdio.h>
42 #include <string.h>
43 #include <inttypes.h>
44 
45 #include "classic/avrcp.h"
46 #include "classic/avrcp_target.h"
47 
48 #include "bluetooth_sdp.h"
49 #include "btstack_debug.h"
50 #include "btstack_event.h"
51 #include "btstack_util.h"
52 #include "l2cap.h"
53 
54 #define AVRCP_ATTR_HEADER_LEN  8
55 
56 static const uint8_t AVRCP_NOTIFICATION_TRACK_SELECTED[] = {0,0,0,0,0,0,0,0};
57 static const uint8_t AVRCP_NOTIFICATION_TRACK_NOT_SELECTED[] = {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF};
58 
59 avrcp_context_t avrcp_target_context;
60 
61 static int avrcp_target_supports_browsing(uint16_t target_supported_features){
62     return target_supported_features & AVRCP_FEATURE_MASK_BROWSING;
63 }
64 
65 void avrcp_target_create_sdp_record(uint8_t * service, uint32_t service_record_handle, uint16_t supported_features, const char * service_name, const char * service_provider_name){
66     avrcp_create_sdp_record(0, service, service_record_handle, avrcp_target_supports_browsing(supported_features), supported_features, service_name, service_provider_name);
67 }
68 
69 static void
70 avrcp_target_emit_operation(btstack_packet_handler_t callback, uint16_t avrcp_cid, avrcp_operation_id_t operation_id,
71                             bool button_pressed, uint8_t operands_length, uint8_t operand) {
72     btstack_assert(callback != NULL);
73 
74     uint8_t event[9];
75     int pos = 0;
76     event[pos++] = HCI_EVENT_AVRCP_META;
77     event[pos++] = sizeof(event) - 2;
78     event[pos++] = AVRCP_SUBEVENT_OPERATION;
79     little_endian_store_16(event, pos, avrcp_cid);
80     pos += 2;
81     event[pos++] = operation_id;
82     event[pos++] = button_pressed ? 1 : 0;
83     event[pos++] = operands_length;
84     event[pos++] = operand;
85     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
86 }
87 
88 static void avrcp_target_emit_volume_changed(btstack_packet_handler_t callback, uint16_t avrcp_cid, uint8_t absolute_volume){
89     btstack_assert(callback != NULL);
90 
91     uint8_t event[7];
92     int offset = 0;
93     event[offset++] = HCI_EVENT_AVRCP_META;
94     event[offset++] = sizeof(event) - 2;
95     event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_VOLUME_CHANGED;
96     little_endian_store_16(event, offset, avrcp_cid);
97     offset += 2;
98     event[offset++] = AVRCP_CTYPE_NOTIFY;
99     event[offset++] = absolute_volume;
100     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
101 }
102 
103 static void avrcp_target_emit_respond_vendor_dependent_query(btstack_packet_handler_t callback, uint16_t avrcp_cid, uint8_t subevent_id){
104     btstack_assert(callback != NULL);
105 
106     uint8_t event[5];
107     int pos = 0;
108     event[pos++] = HCI_EVENT_AVRCP_META;
109     event[pos++] = sizeof(event) - 2;
110     event[pos++] = subevent_id;
111     little_endian_store_16(event, pos, avrcp_cid);
112     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
113 }
114 
115 // returns number of bytes stored
116 static uint16_t avrcp_target_pack_single_element_header(uint8_t * packet, uint16_t pos, avrcp_media_attribute_id_t attr_id, uint16_t attr_value_size){
117     btstack_assert(attr_id >= 1);
118     btstack_assert(attr_id <= AVRCP_MEDIA_ATTR_COUNT);
119 
120     big_endian_store_32(packet, pos, attr_id);
121     big_endian_store_16(packet, pos+4, RFC2978_CHARSET_MIB_UTF8);
122     big_endian_store_16(packet, pos+6, attr_value_size);
123     return 8;
124 }
125 
126 // returns number of bytes stored
127 static uint16_t avrcp_target_pack_single_element_attribute_number(uint8_t * packet, uint16_t pos, avrcp_media_attribute_id_t attr_id, uint32_t value){
128     uint16_t attr_value_length = sprintf((char *)(packet+pos+8), "%0" PRIu32, value);
129     (void) avrcp_target_pack_single_element_header(packet, pos, attr_id, attr_value_length);
130     return 8 + attr_value_length;
131 }
132 
133 // returns number of bytes stored
134 static uint16_t avrcp_target_pack_single_element_attribute_string_fragment(uint8_t * packet, uint16_t pos, avrcp_media_attribute_id_t attr_id, uint8_t * attr_value, uint16_t attr_value_to_copy, uint16_t attr_value_size, bool header){
135     if (attr_value_size == 0) return 0;
136     uint16_t bytes_stored = 0;
137     if (header){
138         bytes_stored += avrcp_target_pack_single_element_header(packet, pos, attr_id, attr_value_size);
139     }
140     (void)memcpy(packet + pos + bytes_stored, attr_value, attr_value_to_copy);
141     bytes_stored += attr_value_to_copy;
142     return bytes_stored;
143 }
144 
145 static int avrcp_target_abort_continue_response(uint16_t cid, avrcp_connection_t * connection){
146     uint16_t pos = 0;
147     l2cap_reserve_packet_buffer();
148     uint8_t * packet = l2cap_get_outgoing_buffer();
149 
150     connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
151     connection->command_type    = AVRCP_CTYPE_RESPONSE_ACCEPTED;
152     connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
153     connection->subunit_id      = AVRCP_SUBUNIT_ID;
154 
155     packet[pos++] = (connection->transaction_id << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
156     // Profile IDentifier (PID)
157     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
158     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
159 
160     // command_type
161     packet[pos++] = connection->command_type;
162     // subunit_type | subunit ID
163     packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
164     // opcode
165     packet[pos++] = (uint8_t)connection->command_opcode;
166 
167     // company id is 3 bytes long
168     big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
169     pos += 3;
170 
171     packet[pos++] = AVRCP_PDU_ID_REQUEST_ABORT_CONTINUING_RESPONSE;
172 
173     // reserve byte for packet type
174     packet[pos++] = AVRCP_SINGLE_PACKET;
175     big_endian_store_16(packet, pos, 0);
176     pos += 2;
177     return l2cap_send_prepared(cid, pos);
178 }
179 
180 static int avrcp_target_send_now_playing_info(uint16_t cid, avrcp_connection_t * connection){
181     uint16_t pos = 0;
182     l2cap_reserve_packet_buffer();
183     uint8_t * packet = l2cap_get_outgoing_buffer();
184     uint16_t  size   = l2cap_get_remote_mtu_for_local_cid(connection->l2cap_signaling_cid);
185 
186     packet[pos++] = (connection->transaction_id << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
187     // Profile IDentifier (PID)
188     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
189     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
190 
191     // command_type
192     packet[pos++] = connection->command_type;
193     // subunit_type | subunit ID
194     packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
195     // opcode
196     packet[pos++] = (uint8_t)connection->command_opcode;
197 
198     // company id is 3 bytes long
199     big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
200     pos += 3;
201 
202     packet[pos++] = AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES;
203 
204     // reserve byte for packet type
205     uint8_t pos_packet_type = pos;
206     pos++;
207 
208     uint16_t playing_info_buffer_len_position = pos;
209     pos += 2;
210     if (connection->next_attr_id == AVRCP_MEDIA_ATTR_NONE){
211         packet[pos_packet_type] = AVRCP_SINGLE_PACKET;
212         connection->packet_type = AVRCP_SINGLE_PACKET;
213         packet[pos++] = count_set_bits_uint32(connection->now_playing_info_attr_bitmap);
214         connection->next_attr_id = AVRCP_MEDIA_ATTR_ALL;
215     }
216 
217     uint8_t fragmented = 0;
218     int num_free_bytes = size - pos - 2;
219     uint8_t MAX_NUMBER_ATTR_LEN = 10;
220 
221     while (!fragmented && (num_free_bytes > 0) && (connection->next_attr_id <= AVRCP_MEDIA_ATTR_SONG_LENGTH_MS)){
222         avrcp_media_attribute_id_t attr_id = connection->next_attr_id;
223         int attr_index = attr_id - 1;
224 
225         if (connection->now_playing_info_attr_bitmap & (1 << attr_id)){
226             int num_written_bytes = 0;
227             int num_bytes_to_write = 0;
228             switch (attr_id){
229                 case AVRCP_MEDIA_ATTR_ALL:
230                 case AVRCP_MEDIA_ATTR_NONE:
231                     break;
232                 case AVRCP_MEDIA_ATTR_TRACK:
233                     num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
234                     if (num_free_bytes >= num_bytes_to_write){
235                         num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->track_nr);
236                         break;
237                     }
238                     fragmented = 1;
239                     connection->attribute_value_offset = 0;
240                     break;
241                 case AVRCP_MEDIA_ATTR_TOTAL_NUM_ITEMS:
242                     num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
243                     if (num_free_bytes >= num_bytes_to_write){
244                         num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->total_tracks);
245                         break;
246                     }
247                     fragmented = 1;
248                     connection->attribute_value_offset = 0;
249                     break;
250                 case AVRCP_MEDIA_ATTR_SONG_LENGTH_MS:
251                     num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
252                     if (num_free_bytes >= num_bytes_to_write){
253                         num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->song_length_ms);
254                         break;
255                     }
256                     fragmented = 1;
257                     connection->attribute_value_offset = 0;
258                     break;
259                 default:{
260                     bool      header = connection->attribute_value_offset == 0;
261                     uint8_t * attr_value =     (uint8_t *) (connection->now_playing_info[attr_index].value + connection->attribute_value_offset);
262                     uint16_t  attr_value_len = connection->now_playing_info[attr_index].len - connection->attribute_value_offset;
263 
264                     num_bytes_to_write = attr_value_len + (header * AVRCP_ATTR_HEADER_LEN);
265                     if (num_bytes_to_write <= num_free_bytes){
266                         connection->attribute_value_offset = 0;
267                         num_written_bytes = num_bytes_to_write;
268                         avrcp_target_pack_single_element_attribute_string_fragment(packet, pos, attr_id, attr_value, attr_value_len, connection->now_playing_info[attr_index].len, header);
269                         break;
270                     }
271                     fragmented = 1;
272                     num_written_bytes = num_free_bytes;
273                     attr_value_len = num_free_bytes - (header * AVRCP_ATTR_HEADER_LEN);
274                     avrcp_target_pack_single_element_attribute_string_fragment(packet, pos, attr_id, attr_value, attr_value_len, connection->now_playing_info[attr_index].len, header);
275                     connection->attribute_value_offset += attr_value_len;
276                     break;
277                 }
278             }
279             pos += num_written_bytes;
280             num_free_bytes -= num_written_bytes;
281         }
282         if (!fragmented){
283             // C++ compatible version of connection->next_attr_id++
284             connection->next_attr_id = (avrcp_media_attribute_id_t) (((int) connection->next_attr_id) + 1);
285         }
286     }
287 
288     if (fragmented){
289         switch (connection->packet_type){
290             case AVRCP_SINGLE_PACKET:
291                 connection->packet_type = AVRCP_START_PACKET;
292                 break;
293             default:
294                 connection->packet_type = AVRCP_CONTINUE_PACKET;
295                 break;
296         }
297     } else {
298         if (connection->next_attr_id >= AVRCP_MEDIA_ATTR_SONG_LENGTH_MS){ // DONE
299             if (connection->packet_type != AVRCP_SINGLE_PACKET){
300                 connection->packet_type = AVRCP_END_PACKET;
301             }
302         }
303     }
304     packet[pos_packet_type] = connection->packet_type;
305     // store attr value length
306     big_endian_store_16(packet, playing_info_buffer_len_position, pos - playing_info_buffer_len_position - 2);
307     return l2cap_send_prepared(cid, size);
308 }
309 
310 
311 
312 static int avrcp_target_send_response(uint16_t cid, avrcp_connection_t * connection){
313     int pos = 0;
314     l2cap_reserve_packet_buffer();
315     uint8_t * packet = l2cap_get_outgoing_buffer();
316 
317     // transport header
318     // Transaction label | Packet_type | C/R | IPID (1 == invalid profile identifier)
319 
320     // TODO: check for fragmentation
321     connection->packet_type = AVRCP_SINGLE_PACKET;
322 
323     packet[pos++] = (connection->transaction_id << 4) | (connection->packet_type << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
324     // Profile IDentifier (PID)
325     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
326     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
327     // command_type
328     packet[pos++] = connection->command_type;
329     // subunit_type | subunit ID
330     packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
331     // opcode
332     packet[pos++] = (uint8_t)connection->command_opcode;
333 
334     (void)memcpy(packet + pos, connection->cmd_operands,
335                  connection->cmd_operands_length);
336     pos += connection->cmd_operands_length;
337 
338     return l2cap_send_prepared(cid, pos);
339 }
340 
341 static void avrcp_target_response_setup(avrcp_connection_t * connection, avrcp_command_type_t command_type, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id,
342                                         avrcp_command_opcode_t opcode){
343     connection->command_type = command_type;
344     connection->subunit_type = subunit_type;
345     connection->subunit_id =   subunit_id;
346     connection->command_opcode = opcode;
347 }
348 
349 static uint8_t avrcp_target_response_accept(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id, uint8_t status){
350     // AVRCP_CTYPE_RESPONSE_REJECTED
351     avrcp_target_response_setup(connection, AVRCP_CTYPE_RESPONSE_ACCEPTED, subunit_type, subunit_id, opcode);
352     // company id is 3 bytes long
353     int pos = connection->cmd_operands_length;
354     connection->cmd_operands[pos++] = pdu_id;
355     connection->cmd_operands[pos++] = 0;
356     // param length
357     big_endian_store_16(connection->cmd_operands, pos, 1);
358     pos += 2;
359     connection->cmd_operands[pos++] = status;
360     connection->cmd_operands_length = pos;
361     connection->accept_response = 1;
362     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
363     return ERROR_CODE_SUCCESS;
364 }
365 
366 static uint8_t avrcp_target_response_reject(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id, avrcp_status_code_t status){
367     // AVRCP_CTYPE_RESPONSE_REJECTED
368     avrcp_target_response_setup(connection, AVRCP_CTYPE_RESPONSE_REJECTED, subunit_type, subunit_id, opcode);
369     // company id is 3 bytes long
370     int pos = connection->cmd_operands_length;
371     connection->cmd_operands[pos++] = pdu_id;
372     connection->cmd_operands[pos++] = 0;
373     // param length
374     big_endian_store_16(connection->cmd_operands, pos, 1);
375     pos += 2;
376     connection->cmd_operands[pos++] = status;
377     connection->cmd_operands_length = pos;
378     connection->state = AVCTP_W2_SEND_RESPONSE;
379     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
380     return ERROR_CODE_SUCCESS;
381 }
382 
383 static uint8_t avrcp_target_response_not_implemented(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id, uint8_t event_id){
384     avrcp_target_response_setup(connection, AVRCP_CTYPE_RESPONSE_NOT_IMPLEMENTED, subunit_type, subunit_id, opcode);
385     // company id is 3 bytes long
386     int pos = connection->cmd_operands_length;
387     connection->cmd_operands[pos++] = pdu_id;
388     connection->cmd_operands[pos++] = 0;
389     // param length
390     big_endian_store_16(connection->cmd_operands, pos, 1);
391     pos += 2;
392     connection->cmd_operands[pos++] = event_id;
393     connection->cmd_operands_length = pos;
394 
395     connection->state = AVCTP_W2_SEND_RESPONSE;
396     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
397     return ERROR_CODE_SUCCESS;
398 }
399 
400 static uint8_t avrcp_target_response_vendor_dependent_interim(avrcp_connection_t * connection, avrcp_pdu_id_t pdu_id, uint8_t event_id, const uint8_t * value, uint16_t value_len){
401 
402     // company id is 3 bytes long
403     int pos = connection->cmd_operands_length;
404     connection->cmd_operands[pos++] = pdu_id;
405     connection->cmd_operands[pos++] = 0;
406     // param length
407     big_endian_store_16(connection->cmd_operands, pos, 1 + value_len);
408     pos += 2;
409     connection->cmd_operands[pos++] = event_id;
410     if (value && (value_len > 0)){
411         (void)memcpy(connection->cmd_operands + pos, value, value_len);
412         pos += value_len;
413     }
414     connection->cmd_operands_length = pos;
415     connection->state = AVCTP_W2_SEND_RESPONSE;
416     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
417     return ERROR_CODE_SUCCESS;
418 }
419 
420 static uint8_t avrcp_target_response_addressed_player_changed_interim(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id){
421     avrcp_target_response_setup(connection, AVRCP_CTYPE_RESPONSE_INTERIM, subunit_type, subunit_id, opcode);
422 
423     // company id is 3 bytes long
424     int pos = connection->cmd_operands_length;
425     connection->cmd_operands[pos++] = pdu_id;
426     connection->cmd_operands[pos++] = 0;
427     // param length
428     big_endian_store_16(connection->cmd_operands, pos, 5);
429     pos += 2;
430     connection->cmd_operands[pos++] = AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED;
431     big_endian_read_16( &connection->cmd_operands[pos], connection->addressed_player_id);
432     pos += 2;
433     big_endian_read_16( &connection->cmd_operands[pos], connection->uid_counter);
434     pos += 2;
435 
436     connection->cmd_operands_length = pos;
437     connection->state = AVCTP_W2_SEND_RESPONSE;
438     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
439     return ERROR_CODE_SUCCESS;
440 }
441 
442 static uint8_t avrcp_target_pass_through_response(uint16_t avrcp_cid, avrcp_command_type_t cmd_type, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
443     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
444     if (!connection){
445         log_error("Could not find a connection.");
446         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
447     }
448     avrcp_target_response_setup(connection, cmd_type, AVRCP_SUBUNIT_TYPE_PANEL, AVRCP_SUBUNIT_ID, AVRCP_CMD_OPCODE_PASS_THROUGH);
449 
450     int pos = 0;
451     connection->cmd_operands[pos++] = opid;
452     connection->cmd_operands[pos++] = operands_length;
453     if (operands_length == 1){
454         connection->cmd_operands[pos++] = operand;
455     }
456     connection->cmd_operands_length = pos;
457 
458     connection->state = AVCTP_W2_SEND_RESPONSE;
459     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
460     return ERROR_CODE_SUCCESS;
461 }
462 
463 uint8_t avrcp_target_operation_rejected(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
464     return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_REJECTED, opid, operands_length, operand);
465 }
466 
467 uint8_t avrcp_target_operation_accepted(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
468     return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_ACCEPTED, opid, operands_length, operand);
469 }
470 
471 uint8_t avrcp_target_operation_not_implemented(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
472     return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_ACCEPTED, opid, operands_length, operand);
473 }
474 
475 uint8_t avrcp_target_set_unit_info(uint16_t avrcp_cid, avrcp_subunit_type_t unit_type, uint32_t company_id){
476     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
477     if (!connection){
478         log_error("avrcp_target_set_unit_info: could not find a connection.");
479         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
480     }
481     connection->unit_type = unit_type;
482     connection->company_id = company_id;
483     return ERROR_CODE_SUCCESS;
484 }
485 
486 uint8_t avrcp_target_set_subunit_info(uint16_t avrcp_cid, avrcp_subunit_type_t subunit_type, const uint8_t * subunit_info_data, uint16_t subunit_info_data_size){
487     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
488     if (!connection){
489         log_error("avrcp_target_set_subunit_info: could not find a connection.");
490         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
491     }
492     connection->subunit_info_type = subunit_type;
493     connection->subunit_info_data = subunit_info_data;
494     connection->subunit_info_data_size = subunit_info_data_size;
495     return ERROR_CODE_SUCCESS;
496 }
497 
498 static uint8_t avrcp_target_unit_info(avrcp_connection_t * connection){
499     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
500 
501     uint8_t unit = 0;
502     connection->command_type = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
503     connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
504     connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
505     connection->command_opcode = AVRCP_CMD_OPCODE_UNIT_INFO;
506 
507     connection->cmd_operands_length = 5;
508     connection->cmd_operands[0] = 0x07;
509     connection->cmd_operands[1] = (connection->unit_type << 4) | unit;
510     // company id is 3 bytes long
511     big_endian_store_32(connection->cmd_operands, 2, connection->company_id);
512 
513     connection->state = AVCTP_W2_SEND_RESPONSE;
514     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
515     return ERROR_CODE_SUCCESS;
516 }
517 
518 
519 static uint8_t avrcp_target_subunit_info(avrcp_connection_t * connection, uint8_t offset){
520     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
521     if (offset >= 32) return AVRCP_STATUS_INVALID_PARAMETER;
522 
523     connection->command_opcode = AVRCP_CMD_OPCODE_SUBUNIT_INFO;
524     connection->command_type = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
525     connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
526     connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
527 
528     uint8_t page = offset / 4;
529     uint8_t extension_code = 7;
530     connection->cmd_operands_length = 5;
531     connection->cmd_operands[0] = (page << 4) | extension_code;
532 
533     // mark non-existent entries with 0xff
534     memset(&connection->cmd_operands[1], 0xff, 4);
535     if ((connection->subunit_info_data != NULL) && (offset < connection->subunit_info_data_size)){
536         uint8_t bytes_to_copy = btstack_min(connection->subunit_info_data_size - offset, 4);
537         memcpy(&connection->cmd_operands[1], &connection->subunit_info_data[offset], bytes_to_copy);
538     }
539 
540     connection->state = AVCTP_W2_SEND_RESPONSE;
541     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
542     return ERROR_CODE_SUCCESS;
543 }
544 
545 static inline uint8_t avrcp_prepare_vendor_dependent_response(uint16_t avrcp_cid, avrcp_connection_t ** out_connection, avrcp_pdu_id_t pdu_id, uint16_t param_length){
546     *out_connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
547     if (!*out_connection){
548         log_error("avrcp tartget: could not find a connection.");
549         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
550     }
551 
552     if ((*out_connection)->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
553     (*out_connection)->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
554     (*out_connection)->command_type    = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
555     (*out_connection)->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
556     (*out_connection)->subunit_id      = AVRCP_SUBUNIT_ID;
557 
558     (*out_connection)->cmd_operands[(*out_connection)->cmd_operands_length++] = pdu_id;
559     // reserved
560     (*out_connection)->cmd_operands[(*out_connection)->cmd_operands_length++] = 0;
561     // param length
562     big_endian_store_16((*out_connection)->cmd_operands, (*out_connection)->cmd_operands_length, param_length);
563     (*out_connection)->cmd_operands_length += 2;
564     return ERROR_CODE_SUCCESS;
565 }
566 
567 static uint8_t avrcp_target_capability(uint16_t avrcp_cid, avrcp_capability_id_t capability_id, uint8_t num_capabilities, const uint8_t *capabilities, uint8_t capabilities_size){
568     avrcp_connection_t * connection = NULL;
569     uint8_t status = avrcp_prepare_vendor_dependent_response(avrcp_cid, &connection, AVRCP_PDU_ID_GET_CAPABILITIES, 2 + capabilities_size);
570     if (status != ERROR_CODE_SUCCESS) return status;
571 
572     connection->cmd_operands[connection->cmd_operands_length++] = capability_id;
573     connection->cmd_operands[connection->cmd_operands_length++] = num_capabilities;
574     (void)memcpy(connection->cmd_operands + connection->cmd_operands_length,
575                  capabilities, capabilities_size);
576     connection->cmd_operands_length += capabilities_size;
577 
578     connection->state = AVCTP_W2_SEND_RESPONSE;
579     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
580     return ERROR_CODE_SUCCESS;
581 }
582 
583 uint8_t avrcp_target_supported_events(uint16_t avrcp_cid, uint8_t num_event_ids, const uint8_t *event_ids, uint8_t event_ids_size){
584     return avrcp_target_capability(avrcp_cid, AVRCP_CAPABILITY_ID_EVENT, num_event_ids, event_ids, event_ids_size);
585 }
586 
587 uint8_t avrcp_target_supported_companies(uint16_t avrcp_cid, uint8_t num_company_ids, const uint8_t *company_ids, uint8_t company_ids_size){
588     return avrcp_target_capability(avrcp_cid, AVRCP_CAPABILITY_ID_COMPANY, num_company_ids, company_ids, company_ids_size);
589 }
590 
591 uint8_t avrcp_target_play_status(uint16_t avrcp_cid, uint32_t song_length_ms, uint32_t song_position_ms, avrcp_playback_status_t play_status){
592     avrcp_connection_t * connection = NULL;
593     uint8_t status = avrcp_prepare_vendor_dependent_response(avrcp_cid, &connection, AVRCP_PDU_ID_GET_PLAY_STATUS, 11);
594     if (status != ERROR_CODE_SUCCESS) return status;
595 
596     big_endian_store_32(connection->cmd_operands, connection->cmd_operands_length, song_length_ms);
597     connection->cmd_operands_length += 4;
598     big_endian_store_32(connection->cmd_operands, connection->cmd_operands_length, song_position_ms);
599     connection->cmd_operands_length += 4;
600     connection->cmd_operands[connection->cmd_operands_length++] = play_status;
601 
602     connection->state = AVCTP_W2_SEND_RESPONSE;
603     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
604     return ERROR_CODE_SUCCESS;
605 }
606 
607 static uint8_t avrcp_target_now_playing_info(avrcp_connection_t * connection){
608     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
609     connection->now_playing_info_response = 1;
610     connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
611     connection->command_type    = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
612     connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
613     connection->subunit_id      = AVRCP_SUBUNIT_ID;
614 
615     connection->state = AVCTP_W2_SEND_RESPONSE;
616     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
617     return ERROR_CODE_SUCCESS;
618 }
619 
620 static uint8_t avrcp_target_store_media_attr(avrcp_connection_t * connection, avrcp_media_attribute_id_t attr_id, const char * value){
621     int index = attr_id - 1;
622     if (!value) return AVRCP_STATUS_INVALID_PARAMETER;
623     connection->now_playing_info[index].value = (uint8_t*)value;
624     connection->now_playing_info[index].len   = strlen(value);
625     return ERROR_CODE_SUCCESS;
626 }
627 
628 uint8_t avrcp_target_set_playback_status(uint16_t avrcp_cid, avrcp_playback_status_t playback_status){
629     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
630     if (!connection){
631         log_error("avrcp_unit_info: could not find a connection.");
632         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
633     }
634     if (connection->playback_status == playback_status){
635         return ERROR_CODE_SUCCESS;
636     }
637 
638     connection->playback_status = playback_status;
639     connection->playback_status_changed = 1;
640     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
641     return ERROR_CODE_SUCCESS;
642 }
643 
644 uint8_t avrcp_target_set_now_playing_info(uint16_t avrcp_cid, const avrcp_track_t * current_track, uint16_t total_tracks){
645     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
646     if (!connection){
647         log_error("avrcp_unit_info: could not find a connection. cid 0x%02x\n", avrcp_cid);
648         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
649     }
650     if (!current_track){
651         connection->track_selected = 0;
652         connection->playback_status = AVRCP_PLAYBACK_STATUS_ERROR;
653         return ERROR_CODE_COMMAND_DISALLOWED;
654     }
655 
656     (void)memcpy(connection->track_id, current_track->track_id, 8);
657     connection->song_length_ms = current_track->song_length_ms;
658     connection->track_nr = current_track->track_nr;
659     connection->total_tracks = total_tracks;
660     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_TITLE, current_track->title);
661     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_ARTIST, current_track->artist);
662     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_ALBUM, current_track->album);
663     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_GENRE, current_track->genre);
664     connection->track_selected = 1;
665 
666     if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED)) {
667         connection->track_changed = 1;
668         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
669     } else {
670         return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
671     }
672     return ERROR_CODE_SUCCESS;
673 }
674 
675 uint8_t avrcp_target_track_changed(uint16_t avrcp_cid, uint8_t * track_id){
676     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
677     if (!connection){
678         log_error("avrcp_target_track_changed: could not find connection.");
679         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
680     }
681     if (!track_id){
682         return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
683     }
684 
685     (void)memcpy(connection->track_id, track_id, 8);
686     if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED)) {
687         connection->track_changed = 1;
688         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
689     }
690     return ERROR_CODE_SUCCESS;
691 }
692 
693 uint8_t avrcp_target_playing_content_changed(uint16_t avrcp_cid){
694     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
695     if (!connection){
696         log_error("avrcp_target_playing_content_changed: could not find a connection.");
697         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
698     }
699     if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED)) {
700         connection->playing_content_changed = 1;
701         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
702     }
703     return ERROR_CODE_SUCCESS;
704 }
705 
706 uint8_t avrcp_target_addressed_player_changed(uint16_t avrcp_cid, uint16_t player_id, uint16_t uid_counter){
707     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
708     if (!connection){
709         log_error("avrcp_unit_info: could not find a connection.");
710         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
711     }
712 
713     if (connection->addressed_player_id == player_id){
714         return ERROR_CODE_SUCCESS;
715     }
716 
717     connection->uid_counter = uid_counter;
718     connection->addressed_player_id = player_id;
719 
720     if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED)) {
721         connection->addressed_player_changed = 1;
722         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
723     }
724     return ERROR_CODE_SUCCESS;
725 }
726 
727 uint8_t avrcp_target_battery_status_changed(uint16_t avrcp_cid, avrcp_battery_status_t battery_status){
728     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
729     if (!connection){
730         log_error("avrcp_unit_info: could not find a connection.");
731         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
732     }
733     if (connection->battery_status == battery_status){
734         return ERROR_CODE_SUCCESS;
735     }
736 
737     connection->battery_status = battery_status;
738 
739     if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED)) {
740         connection->battery_status_changed = 1;
741         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
742     }
743     return ERROR_CODE_SUCCESS;
744 }
745 
746 uint8_t avrcp_target_volume_changed(uint16_t avrcp_cid, uint8_t volume_percentage){
747     avrcp_connection_t * connection = avrcp_get_connection_for_avrcp_cid_for_role(AVRCP_TARGET, avrcp_cid);
748     if (!connection){
749         log_error("avrcp_unit_info: could not find a connection.");
750         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
751     }
752     if (connection->volume_percentage == volume_percentage){
753         return ERROR_CODE_SUCCESS;
754     }
755 
756     connection->volume_percentage = volume_percentage;
757 
758     if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED )) {
759         connection->notify_volume_percentage_changed = 1;
760         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
761     }
762     return ERROR_CODE_SUCCESS;
763 }
764 
765 static void avrcp_target_set_transaction_label_for_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t notification, uint8_t transaction_label){
766     if (notification > AVRCP_NOTIFICATION_EVENT_MAX_VALUE) return;
767     connection->notifications_transaction_label[notification] = transaction_label;
768 }
769 
770 static uint8_t avrcp_target_get_transaction_label_for_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t notification){
771     if (notification > AVRCP_NOTIFICATION_EVENT_MAX_VALUE) return 0;
772     return connection->notifications_transaction_label[notification];
773 }
774 
775 static bool avcrp_operation_id_is_valid(avrcp_operation_id_t operation_id){
776     if (operation_id < AVRCP_OPERATION_ID_RESERVED_1) return true;
777 
778     if (operation_id < AVRCP_OPERATION_ID_0) return false;
779     if (operation_id < AVRCP_OPERATION_ID_RESERVED_2) return true;
780 
781     if (operation_id < AVRCP_OPERATION_ID_CHANNEL_UP) return false;
782     if (operation_id < AVRCP_OPERATION_ID_RESERVED_3) return true;
783 
784     if (operation_id < AVRCP_OPERATION_ID_CHANNEL_UP) return false;
785     if (operation_id < AVRCP_OPERATION_ID_RESERVED_3) return true;
786 
787     if (operation_id < AVRCP_OPERATION_ID_SKIP) return false;
788     if (operation_id == AVRCP_OPERATION_ID_SKIP) return true;
789 
790     if (operation_id < AVRCP_OPERATION_ID_POWER) return false;
791     if (operation_id < AVRCP_OPERATION_ID_RESERVED_4) return true;
792 
793     if (operation_id < AVRCP_OPERATION_ID_ANGLE) return false;
794     if (operation_id < AVRCP_OPERATION_ID_RESERVED_5) return true;
795 
796     if (operation_id < AVRCP_OPERATION_ID_F1) return false;
797     if (operation_id < AVRCP_OPERATION_ID_RESERVED_6) return true;
798 
799     return false;
800 }
801 
802 static void avrcp_handle_l2cap_data_packet_for_signaling_connection(avrcp_connection_t * connection, uint8_t *packet, uint16_t size){
803 
804     if (size < 6u) return;
805 
806     uint16_t pid = 0;
807     uint8_t transport_header = packet[0];
808     connection->transaction_id = transport_header >> 4;
809 
810     avrcp_packet_type_t packet_type = (avrcp_packet_type_t) ((transport_header & 0x0F) >> 2);
811     switch (packet_type){
812         case AVRCP_SINGLE_PACKET:
813             pid =  big_endian_read_16(packet, 1);
814             break;
815         case AVRCP_START_PACKET:
816             pid =  big_endian_read_16(packet, 2);
817             break;
818         default:
819             break;
820     }
821 
822     switch (packet_type){
823         case AVRCP_SINGLE_PACKET:
824         case AVRCP_START_PACKET:
825             if (pid != BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL){
826                 log_info("Invalid pid 0x%02x, expected 0x%02x", connection->invalid_pid, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL);
827                 connection->reject_transport_header = 1;
828                 connection->invalid_pid = pid;
829                 connection->transport_header = (connection->transaction_id << 4) | (AVRCP_SINGLE_PACKET << 2 ) | (AVRCP_RESPONSE_FRAME << 1) | 1;
830                 connection->state = AVCTP_W2_SEND_RESPONSE;
831                 avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
832                 return;
833             }
834             break;
835         default:
836             break;
837     }
838 
839     if (packet_type != AVRCP_SINGLE_PACKET) return;
840 
841     avrcp_subunit_type_t subunit_type = (avrcp_subunit_type_t) (packet[4] >> 3);
842     avrcp_subunit_id_t   subunit_id   = (avrcp_subunit_id_t) (packet[4] & 0x07);
843 
844     avrcp_command_opcode_t opcode = (avrcp_command_opcode_t) avrcp_cmd_opcode(packet,size);
845 
846     int pos = 6;
847     uint16_t length;
848     avrcp_pdu_id_t   pdu_id;
849     connection->cmd_operands_length = 0;
850     uint8_t offset;
851     uint8_t operand;
852     uint16_t event_mask;
853     avrcp_operation_id_t operation_id;
854 
855     switch (opcode){
856         case AVRCP_CMD_OPCODE_UNIT_INFO:
857             avrcp_target_unit_info(connection);
858             break;
859         case AVRCP_CMD_OPCODE_SUBUNIT_INFO:
860             if ((size - pos) < 3) return;
861             // page: packet[pos] >> 4,
862             offset =  4 * (packet[pos]>>4);
863             // extension code (fixed 7) = packet[pos] & 0x0F
864             // 4 bytes paga data, all 0xFF
865             avrcp_target_subunit_info(connection, offset);
866             break;
867 
868         case AVRCP_CMD_OPCODE_PASS_THROUGH:
869             if (size < 8) return;
870             log_info("AVRCP_OPERATION_ID 0x%02x, operands length %d", packet[6], packet[7]);
871             operation_id = (avrcp_operation_id_t) (packet[6] & 0x7f);
872             operand = 0;
873             if ((packet[7] >= 1) && (size >= 9)){
874                 operand = packet[8];
875             }
876 
877             if (avcrp_operation_id_is_valid(operation_id)){
878                 bool button_pressed = (packet[6] & 0x80) == 0;
879 
880                 avrcp_target_operation_accepted(connection->avrcp_cid, (avrcp_operation_id_t) packet[6], packet[7], operand);
881                 avrcp_target_emit_operation(avrcp_target_context.avrcp_callback, connection->avrcp_cid,
882                                                 operation_id, button_pressed, packet[7], operand);
883             } else {
884                 avrcp_target_operation_not_implemented(connection->avrcp_cid, (avrcp_operation_id_t) packet[6], packet[7], operand);
885             }
886             break;
887 
888 
889         case AVRCP_CMD_OPCODE_VENDOR_DEPENDENT:
890 
891             if (size < 13) return;
892 
893             // pos = 6 - company id
894             (void)memcpy(connection->cmd_operands, &packet[pos], 3);
895             connection->cmd_operands_length = 3;
896             pos += 3;
897             // pos = 9
898             pdu_id = (avrcp_pdu_id_t) packet[pos++];
899             // 1 - reserved
900             pos++;
901             // 2-3 param length,
902             length = big_endian_read_16(packet, pos);
903             pos += 2;
904             // pos = 13
905             switch (pdu_id){
906                 case AVRCP_PDU_ID_SET_ADDRESSED_PLAYER:{
907                     if ((pos + 2) > size) return;
908                     bool ok = length == 4;
909                     if (avrcp_target_context.set_addressed_player_callback != NULL){
910                         uint16_t player_id = big_endian_read_16(packet, pos);
911                         ok = avrcp_target_context.set_addressed_player_callback(player_id);
912                     }
913                     if (ok){
914                         avrcp_target_response_accept(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_SUCCESS);
915                     } else {
916                         avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PLAYER_ID);
917                     }
918                     break;
919                 }
920                 case AVRCP_PDU_ID_GET_CAPABILITIES:{
921                     avrcp_capability_id_t capability_id = (avrcp_capability_id_t) packet[pos];
922                     switch (capability_id){
923                         case AVRCP_CAPABILITY_ID_EVENT:
924                             avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_EVENT_IDS_QUERY);
925                             break;
926                         case AVRCP_CAPABILITY_ID_COMPANY:
927                             avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_COMPANY_IDS_QUERY);
928                             break;
929                         default:
930                             avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
931                             break;
932                     }
933                     break;
934                 }
935                 case AVRCP_PDU_ID_GET_PLAY_STATUS:
936                     avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_PLAY_STATUS_QUERY);
937                     break;
938                 case AVRCP_PDU_ID_REQUEST_ABORT_CONTINUING_RESPONSE:
939                     if ((pos + 1) > size) return;
940                     connection->cmd_operands[0] = packet[pos];
941                     connection->abort_continue_response = 1;
942                     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
943                     break;
944                 case AVRCP_PDU_ID_REQUEST_CONTINUING_RESPONSE:
945                     if ((pos + 1) > size) return;
946                     if (packet[pos] != AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES){
947                         avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
948                         return;
949                     }
950                     connection->now_playing_info_response = 1;
951                     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
952                     break;
953                 case AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES:{
954                     if ((pos + 9) > size) return;
955                     uint8_t play_identifier[8];
956                     memset(play_identifier, 0, 8);
957                     if (memcmp(&packet[pos], play_identifier, 8) != 0) {
958                         avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
959                         return;
960                     }
961                     pos += 8;
962                     uint8_t attribute_count = packet[pos++];
963                     connection->next_attr_id = AVRCP_MEDIA_ATTR_NONE;
964                     if (!attribute_count){
965                         connection->now_playing_info_attr_bitmap = 0xFE;
966                     } else {
967                         int i;
968                         connection->now_playing_info_attr_bitmap = 0;
969                         if ((pos + attribute_count * 2) > size) return;
970                         for (i=0; i < attribute_count; i++){
971                             uint16_t attr_id = big_endian_read_16(packet, pos);
972                             pos += 2;
973                             connection->now_playing_info_attr_bitmap |= (1 << attr_id);
974                         }
975                     }
976                     log_info("now_playing_info_attr_bitmap 0x%02x", connection->now_playing_info_attr_bitmap);
977                     avrcp_target_now_playing_info(connection);
978                     break;
979                 }
980                 case AVRCP_PDU_ID_REGISTER_NOTIFICATION:{
981                     if ((pos + 1) > size) return;
982                     avrcp_notification_event_id_t event_id = (avrcp_notification_event_id_t) packet[pos];
983 
984                     avrcp_target_set_transaction_label_for_notification(connection, event_id, connection->transaction_id);
985 
986                     if (event_id < AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED ||
987                         event_id > AVRCP_NOTIFICATION_EVENT_MAX_VALUE){
988                         avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
989                         return;
990                     }
991 
992                     switch (event_id){
993                         case AVRCP_NOTIFICATION_EVENT_AVAILABLE_PLAYERS_CHANGED:
994                         case AVRCP_NOTIFICATION_EVENT_PLAYER_APPLICATION_SETTING_CHANGED:
995                         case AVRCP_NOTIFICATION_EVENT_UIDS_CHANGED:
996                             avrcp_target_response_not_implemented(connection, subunit_type, subunit_id, opcode, pdu_id, event_id);
997                             return;
998                         default:
999                             break;
1000                     }
1001 
1002                     event_mask = (1 << event_id);
1003                     connection->notifications_enabled |= event_mask;
1004                     avrcp_target_response_setup(connection, AVRCP_CTYPE_RESPONSE_INTERIM, subunit_type, subunit_id, opcode);
1005 
1006                     switch (event_id){
1007                         case AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED:
1008                             if (connection->track_selected){
1009                                 avrcp_target_response_vendor_dependent_interim(connection, pdu_id, event_id, AVRCP_NOTIFICATION_TRACK_SELECTED, 8);
1010                             } else {
1011                                 avrcp_target_response_vendor_dependent_interim(connection, pdu_id, event_id, AVRCP_NOTIFICATION_TRACK_NOT_SELECTED, 8);
1012                             }
1013                             break;
1014                         case AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED:
1015                             avrcp_target_response_vendor_dependent_interim(connection, pdu_id, event_id, (const uint8_t *)&connection->playback_status, 1);
1016                             break;
1017                         case AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED:
1018                             avrcp_target_response_vendor_dependent_interim(connection, pdu_id, event_id, NULL, 0);
1019                             break;
1020                         case AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED:
1021                             connection->notify_volume_percentage_changed = 0;
1022                             avrcp_target_response_vendor_dependent_interim(connection, pdu_id, event_id, (const uint8_t *)&connection->volume_percentage, 1);
1023                             break;
1024                         case AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED:
1025                             avrcp_target_response_vendor_dependent_interim(connection, pdu_id, event_id, (const uint8_t *)&connection->battery_status, 1);
1026                             break;
1027                         case AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED:
1028                             avrcp_target_response_addressed_player_changed_interim(connection, subunit_type, subunit_id, opcode, pdu_id);
1029                             return;
1030                         default:
1031                             btstack_assert(false);
1032                             return;
1033                     }
1034                     break;
1035                 }
1036                 case AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME: {
1037                     if (length != 1){
1038                         avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
1039                         break;
1040                     }
1041 
1042                     if ((pos + 1) > size) return;
1043                     uint8_t absolute_volume = packet[pos];
1044                     if (absolute_volume < 0x80){
1045                         connection->volume_percentage = absolute_volume;
1046                     }
1047                     avrcp_target_response_accept(connection, subunit_type, subunit_id, opcode, pdu_id, connection->volume_percentage);
1048                     avrcp_target_emit_volume_changed(avrcp_target_context.avrcp_callback, connection->avrcp_cid, connection->volume_percentage);
1049                     break;
1050                 }
1051                 default:
1052                     log_info("AVRCP target: unhandled pdu id 0x%02x", pdu_id);
1053                     avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
1054                     break;
1055             }
1056             break;
1057         default:
1058             log_info("AVRCP target: opcode 0x%02x not implemented", avrcp_cmd_opcode(packet,size));
1059             break;
1060     }
1061 }
1062 
1063 static int avrcp_target_send_notification(uint16_t cid, avrcp_connection_t * connection, avrcp_notification_event_id_t notification_id, uint8_t * value, uint16_t value_len){
1064     if (!connection){
1065         log_error("avrcp tartget: could not find a connection.");
1066         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1067     }
1068 
1069     btstack_assert((value_len == 0) || (value != NULL));
1070 
1071     connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1072     connection->command_type    = AVRCP_CTYPE_RESPONSE_CHANGED_STABLE;
1073     connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
1074     connection->subunit_id      = AVRCP_SUBUNIT_ID;
1075     connection->transaction_id = avrcp_target_get_transaction_label_for_notification(connection, notification_id);
1076 
1077     uint16_t pos = 0;
1078     l2cap_reserve_packet_buffer();
1079     uint8_t * packet = l2cap_get_outgoing_buffer();
1080 
1081     // value <= 8 ==> pdu <= 22 < L2CAP Default MTU
1082     btstack_assert((14 + value_len) <= l2cap_get_remote_mtu_for_local_cid(connection->l2cap_signaling_cid));
1083 
1084     connection->packet_type = AVRCP_SINGLE_PACKET;
1085     packet[pos++] = (connection->transaction_id << 4) | (connection->packet_type << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
1086     // Profile IDentifier (PID)
1087     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
1088     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
1089 
1090     // command_type
1091     packet[pos++] = connection->command_type;
1092     // subunit_type | subunit ID
1093     packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
1094     // opcode
1095     packet[pos++] = (uint8_t)connection->command_opcode;
1096 
1097     // company id is 3 bytes long
1098     big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
1099     pos += 3;
1100 
1101     packet[pos++] = AVRCP_PDU_ID_REGISTER_NOTIFICATION;
1102     packet[pos++] = 0;
1103 
1104     big_endian_store_16(packet, pos, 1 + value_len);
1105     pos += 2;
1106     packet[pos++] = notification_id;
1107     if (value_len > 0){
1108         (void)memcpy(packet + pos, value, value_len);
1109         pos += value_len;
1110     }
1111 
1112     return l2cap_send_prepared(cid, pos);
1113 }
1114 
1115 static void avrcp_target_reset_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t notification_id){
1116     if (!connection){
1117         log_error("avrcp tartget: could not find a connection.");
1118         return;
1119     }
1120     connection->notifications_enabled &= ~(1 << notification_id);
1121     connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1122     avrcp_target_set_transaction_label_for_notification(connection, notification_id, 0);
1123 }
1124 
1125 static void avrcp_target_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
1126     avrcp_connection_t * connection;
1127     switch (packet_type) {
1128         case L2CAP_DATA_PACKET:
1129             connection = avrcp_get_connection_for_l2cap_signaling_cid_for_role(AVRCP_TARGET, channel);
1130             avrcp_handle_l2cap_data_packet_for_signaling_connection(connection, packet, size);
1131             break;
1132         case HCI_EVENT_PACKET:
1133             switch (hci_event_packet_get_type(packet)){
1134                 case L2CAP_EVENT_CAN_SEND_NOW:{
1135                     connection = avrcp_get_connection_for_l2cap_signaling_cid_for_role(AVRCP_TARGET, channel);
1136 
1137                     if (connection->accept_response){
1138                         connection->accept_response = 0;
1139                         avrcp_target_send_response(connection->l2cap_signaling_cid, connection);
1140                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1141                         return;
1142                     }
1143 
1144                     if (connection->abort_continue_response){
1145                         connection->abort_continue_response = 0;
1146                         connection->now_playing_info_response = 0;
1147                         avrcp_target_abort_continue_response(connection->l2cap_signaling_cid, connection);
1148                         return;
1149                     }
1150 
1151                     if (connection->now_playing_info_response){
1152                         connection->now_playing_info_response = 0;
1153                         avrcp_target_send_now_playing_info(connection->l2cap_signaling_cid, connection);
1154                         return;
1155                     }
1156 
1157                     if (connection->track_changed){
1158                         connection->track_changed = 0;
1159                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED, connection->track_id, 8);
1160                         avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED);
1161                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1162                         return;
1163                     }
1164 
1165                     if (connection->playback_status_changed){
1166                         connection->playback_status_changed = 0;
1167                         uint8_t playback_status = (uint8_t) connection->playback_status;
1168                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED, &playback_status, 1);
1169                         avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED);
1170                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1171                         return;
1172                     }
1173 
1174                     if (connection->playing_content_changed){
1175                         connection->playing_content_changed = 0;
1176                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED, NULL, 0);
1177                         avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED);
1178                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1179                         return;
1180                     }
1181 
1182                     if (connection->battery_status_changed){
1183                         connection->battery_status_changed = 0;
1184                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED, (uint8_t *)&connection->battery_status, 1);
1185                         avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED);
1186                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1187                         return;
1188                     }
1189 
1190                     if (connection->notify_volume_percentage_changed){
1191                         connection->notify_volume_percentage_changed = 0;
1192                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED, &connection->volume_percentage, 1);
1193                         avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED);
1194                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1195                         return;
1196                     }
1197 
1198                     if (connection->addressed_player_changed){
1199                         connection->addressed_player_changed = 0;
1200                         uint8_t buffer[4];
1201                         big_endian_store_16(buffer, 0, connection->addressed_player_id);
1202                         big_endian_store_16(buffer, 2, connection->uid_counter);
1203                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED, buffer, 4);
1204                         avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED);
1205                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1206                         return;
1207                     }
1208 
1209                     if (connection->reject_transport_header){
1210                         connection->state = AVCTP_CONNECTION_OPENED;
1211                         connection->reject_transport_header = 0;
1212                         l2cap_reserve_packet_buffer();
1213                         uint8_t * out_buffer = l2cap_get_outgoing_buffer();
1214                         out_buffer[0] = connection->transport_header;
1215                         big_endian_store_16(out_buffer, 1, connection->invalid_pid);
1216                         l2cap_send_prepared(connection->l2cap_signaling_cid, 3);
1217                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1218                         return;
1219                     }
1220 
1221                     switch (connection->state){
1222                         case AVCTP_W2_SEND_RESPONSE:
1223                             connection->state = AVCTP_CONNECTION_OPENED;
1224                             avrcp_target_send_response(connection->l2cap_signaling_cid, connection);
1225                             avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1226                             return;
1227                         default:
1228                             break;
1229                     }
1230 
1231                     break;
1232             }
1233             default:
1234                 break;
1235         }
1236         default:
1237             break;
1238     }
1239 }
1240 
1241 void avrcp_target_init(void){
1242     avrcp_target_context.role = AVRCP_TARGET;
1243     avrcp_target_context.packet_handler = avrcp_target_packet_handler;
1244     avrcp_register_target_packet_handler(&avrcp_target_packet_handler);
1245 }
1246 
1247 void avrcp_target_deinit(void){
1248     memset(&avrcp_target_context, 0, sizeof(avrcp_context_t));
1249 }
1250 
1251 void avrcp_target_register_packet_handler(btstack_packet_handler_t callback){
1252     btstack_assert(callback != NULL);
1253     avrcp_target_context.avrcp_callback = callback;
1254 }
1255 
1256 void avrcp_target_register_set_addressed_player_handler(bool (*callback)(uint16_t player_id)){
1257     btstack_assert(callback != NULL);
1258     avrcp_target_context.set_addressed_player_callback = callback;
1259 }
1260 
1261 
1262