xref: /btstack/src/classic/avrcp_target.c (revision c37cd8f3d1350b92a2f66c31b2a5fcd75f8c91a4)
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 <stdlib.h>
43 #include <string.h>
44 #include <inttypes.h>
45 
46 #include "btstack.h"
47 #include "classic/avrcp.h"
48 
49 #define AVRCP_ATTR_HEADER_LEN  8
50 
51 static const uint8_t AVRCP_NOTIFICATION_TRACK_SELECTED[] = {0,0,0,0,0,0,0,0};
52 static const uint8_t AVRCP_NOTIFICATION_TRACK_NOT_SELECTED[] = {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF};
53 
54 static avrcp_context_t avrcp_target_context;
55 
56 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){
57     avrcp_create_sdp_record(0, service, service_record_handle, browsing, supported_features, service_name, service_provider_name);
58 }
59 
60 static void avrcp_target_emit_operation(btstack_packet_handler_t callback, uint16_t avrcp_cid, avrcp_operation_id_t operation_id, uint8_t operands_length, uint8_t operand){
61     if (!callback) return;
62     uint8_t event[8];
63     int pos = 0;
64     event[pos++] = HCI_EVENT_AVRCP_META;
65     event[pos++] = sizeof(event) - 2;
66     event[pos++] = AVRCP_SUBEVENT_OPERATION;
67     little_endian_store_16(event, pos, avrcp_cid);
68     pos += 2;
69     event[pos++] = operation_id;
70     event[pos++] = operands_length;
71     event[pos++] = operand;
72     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
73 }
74 
75 static void avrcp_target_emit_respond_vendor_dependent_query(btstack_packet_handler_t callback, uint16_t avrcp_cid, uint8_t subevent_id){
76     if (!callback) return;
77     uint8_t event[5];
78     int pos = 0;
79     event[pos++] = HCI_EVENT_AVRCP_META;
80     event[pos++] = sizeof(event) - 2;
81     event[pos++] = subevent_id;
82     little_endian_store_16(event, pos, avrcp_cid);
83     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
84 }
85 
86 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){
87     if ((attr_id < 1) || (attr_id > AVRCP_MEDIA_ATTR_COUNT)) return 0;
88     uint16_t attr_value_length = sprintf((char *)(packet+pos+8), "%0" PRIu32, value);
89     big_endian_store_32(packet, pos, attr_id);
90     pos += 4;
91     big_endian_store_16(packet, pos, RFC2978_CHARSET_MIB_UTF8);
92     pos += 2;
93     big_endian_store_16(packet, pos, attr_value_length);
94     pos += 2;
95     return 8 + attr_value_length;
96 }
97 
98 static uint16_t avrcp_target_pack_single_element_attribute_string(uint8_t * packet, uint16_t pos, rfc2978_charset_mib_enumid_t mib_enumid, avrcp_media_attribute_id_t attr_id, uint8_t * attr_value, uint16_t attr_value_to_copy, uint16_t attr_value_size, uint8_t header){
99     if (attr_value_size == 0) return 0;
100     if ((attr_id < 1) || (attr_id > AVRCP_MEDIA_ATTR_COUNT)) return 0;
101     if (header){
102         big_endian_store_32(packet, pos, attr_id);
103         pos += 4;
104         big_endian_store_16(packet, pos, mib_enumid);
105         pos += 2;
106         big_endian_store_16(packet, pos, attr_value_size);
107         pos += 2;
108     }
109     memcpy(packet+pos, attr_value, attr_value_to_copy);
110     pos += attr_value_size;
111     return header * 8 + attr_value_size;
112 }
113 
114 static int avrcp_target_abort_continue_response(uint16_t cid, avrcp_connection_t * connection){
115     uint16_t pos = 0;
116     l2cap_reserve_packet_buffer();
117     uint8_t * packet = l2cap_get_outgoing_buffer();
118 
119     connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
120     connection->command_type    = AVRCP_CTYPE_RESPONSE_ACCEPTED;
121     connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
122     connection->subunit_id      = AVRCP_SUBUNIT_ID;
123 
124     packet[pos++] = (connection->transaction_label << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
125     // Profile IDentifier (PID)
126     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
127     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
128 
129     // command_type
130     packet[pos++] = connection->command_type;
131     // subunit_type | subunit ID
132     packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
133     // opcode
134     packet[pos++] = (uint8_t)connection->command_opcode;
135 
136     // company id is 3 bytes long
137     big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
138     pos += 3;
139 
140     packet[pos++] = AVRCP_PDU_ID_REQUEST_ABORT_CONTINUING_RESPONSE;
141 
142     // reserve byte for packet type
143     packet[pos++] = AVRCP_SINGLE_PACKET;
144     big_endian_store_16(packet, pos, 0);
145     pos += 2;
146     return l2cap_send_prepared(cid, pos);
147 }
148 
149 static int avrcp_target_send_now_playing_info(uint16_t cid, avrcp_connection_t * connection){
150     uint16_t pos = 0;
151     l2cap_reserve_packet_buffer();
152     uint8_t * packet = l2cap_get_outgoing_buffer();
153     uint16_t  size   = l2cap_get_remote_mtu_for_local_cid(connection->l2cap_signaling_cid);
154 
155     packet[pos++] = (connection->transaction_label << 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_GET_ELEMENT_ATTRIBUTES;
172 
173     // reserve byte for packet type
174     uint8_t pos_packet_type = pos;
175     pos++;
176 
177     uint16_t playing_info_buffer_len_position = pos;
178     pos += 2;
179     // printf("connection->next_attr_id %d \n", connection->next_attr_id);
180     if (connection->next_attr_id == AVRCP_MEDIA_ATTR_NONE){
181         packet[pos_packet_type] = AVRCP_SINGLE_PACKET;
182         connection->packet_type = AVRCP_SINGLE_PACKET;
183         packet[pos++] = count_set_bits_uint32(connection->now_playing_info_attr_bitmap);
184         connection->next_attr_id++;
185     }
186     // printf("updated connection->next_attr_id %d, connection->attribute_value_offset %d \n", connection->next_attr_id, connection->attribute_value_offset);
187 
188     uint8_t fragmented = 0;
189     int num_free_bytes = size - pos - 2;
190     uint8_t MAX_NUMBER_ATTR_LEN = 10;
191 
192     while (!fragmented && num_free_bytes > 0 && connection->next_attr_id <= AVRCP_MEDIA_ATTR_SONG_LENGTH_MS){
193         avrcp_media_attribute_id_t attr_id = connection->next_attr_id;
194         int attr_index = attr_id - 1;
195 
196         if (connection->now_playing_info_attr_bitmap & (1 << attr_id)){
197             int num_written_bytes = 0;
198             int num_bytes_to_write = 0;
199             switch (attr_id){
200                 case AVRCP_MEDIA_ATTR_ALL:
201                 case AVRCP_MEDIA_ATTR_NONE:
202                     break;
203                 case AVRCP_MEDIA_ATTR_TRACK:
204                     num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
205                     if (num_free_bytes >= num_bytes_to_write){
206                         num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->track_nr);
207                         break;
208                     }
209                     fragmented = 1;
210                     connection->attribute_value_offset = 0;
211                     break;
212                 case AVRCP_MEDIA_ATTR_TOTAL_TRACKS:
213                     num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
214                     if (num_free_bytes >= num_bytes_to_write){
215                         num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->total_tracks);
216                         break;
217                     }
218                     fragmented = 1;
219                     connection->attribute_value_offset = 0;
220                     break;
221                 case AVRCP_MEDIA_ATTR_SONG_LENGTH_MS:
222                     num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
223                     if (num_free_bytes >= num_bytes_to_write){
224                         num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->song_length_ms);
225                         break;
226                     }
227                     fragmented = 1;
228                     connection->attribute_value_offset = 0;
229                     break;
230                 default:{
231                     uint8_t   header = (connection->attribute_value_offset == 0);
232                     uint8_t * attr_value =     (uint8_t *) (connection->now_playing_info[attr_index].value + connection->attribute_value_offset);
233                     uint16_t  attr_value_len = connection->now_playing_info[attr_index].len - connection->attribute_value_offset;
234 
235                     num_bytes_to_write = attr_value_len + header * AVRCP_ATTR_HEADER_LEN;
236                     if (num_bytes_to_write <= num_free_bytes){
237                         connection->attribute_value_offset = 0;
238                         num_written_bytes = num_bytes_to_write;
239                         avrcp_target_pack_single_element_attribute_string(packet, pos, RFC2978_CHARSET_MIB_UTF8, attr_id, attr_value, attr_value_len, connection->now_playing_info[attr_index].len, header);
240                         break;
241                     }
242                     fragmented = 1;
243                     num_written_bytes = num_free_bytes;
244                     attr_value_len = num_free_bytes - header * AVRCP_ATTR_HEADER_LEN;
245                     avrcp_target_pack_single_element_attribute_string(packet, pos, RFC2978_CHARSET_MIB_UTF8, attr_id, attr_value, attr_value_len, connection->now_playing_info[attr_index].len, header);
246                     connection->attribute_value_offset += attr_value_len;
247                     break;
248                 }
249             }
250             pos += num_written_bytes;
251             num_free_bytes -= num_written_bytes;
252         }
253         if (!fragmented){
254             connection->next_attr_id++;
255         }
256     }
257 
258     if (fragmented){
259         switch (connection->packet_type){
260             case AVRCP_SINGLE_PACKET:
261                 connection->packet_type = AVRCP_START_PACKET;
262                 break;
263             default:
264                 connection->packet_type = AVRCP_CONTINUE_PACKET;
265                 break;
266         }
267     } else {
268         if (connection->next_attr_id >= AVRCP_MEDIA_ATTR_SONG_LENGTH_MS){ // DONE
269             if (connection->packet_type != AVRCP_SINGLE_PACKET){
270                 connection->packet_type = AVRCP_END_PACKET;
271             }
272         }
273     }
274     packet[pos_packet_type] = connection->packet_type;
275     // store attr value length
276     big_endian_store_16(packet, playing_info_buffer_len_position, pos - playing_info_buffer_len_position - 2);
277     return l2cap_send_prepared(cid, size);
278 }
279 
280 
281 
282 static int avrcp_target_send_response(uint16_t cid, avrcp_connection_t * connection){
283     int pos = 0;
284     l2cap_reserve_packet_buffer();
285     uint8_t * packet = l2cap_get_outgoing_buffer();
286 
287     // transport header
288     // Transaction label | Packet_type | C/R | IPID (1 == invalid profile identifier)
289 
290     // TODO: check for fragmentation
291     connection->packet_type = AVRCP_SINGLE_PACKET;
292 
293     packet[pos++] = (connection->transaction_label << 4) | (connection->packet_type << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
294     // Profile IDentifier (PID)
295     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
296     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
297     // command_type
298     packet[pos++] = connection->command_type;
299     // subunit_type | subunit ID
300     packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
301     // opcode
302     packet[pos++] = (uint8_t)connection->command_opcode;
303     // operands
304     memcpy(packet+pos, connection->cmd_operands, connection->cmd_operands_length);
305     // printf_hexdump(packet+pos, connection->cmd_operands_length);
306 
307     pos += connection->cmd_operands_length;
308     connection->wait_to_send = 0;
309     return l2cap_send_prepared(cid, pos);
310 }
311 
312 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){
313     // AVRCP_CTYPE_RESPONSE_REJECTED
314     connection->command_type = AVRCP_CTYPE_RESPONSE_REJECTED;
315     connection->subunit_type = subunit_type;
316     connection->subunit_id =   subunit_id;
317     connection->command_opcode = opcode;
318     // company id is 3 bytes long
319     int pos = connection->cmd_operands_length;
320     connection->cmd_operands[pos++] = pdu_id;
321     connection->cmd_operands[pos++] = 0;
322     // param length
323     big_endian_store_16(connection->cmd_operands, pos, 1);
324     pos += 2;
325     connection->cmd_operands[pos++] = status;
326     connection->cmd_operands_length = pos;
327     connection->state = AVCTP_W2_SEND_RESPONSE;
328     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
329     return ERROR_CODE_SUCCESS;
330 }
331 
332 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){
333     connection->command_type = AVRCP_CTYPE_RESPONSE_NOT_IMPLEMENTED;
334     connection->subunit_type = subunit_type;
335     connection->subunit_id =   subunit_id;
336     connection->command_opcode = opcode;
337 
338     // company id is 3 bytes long
339     int pos = connection->cmd_operands_length;
340     connection->cmd_operands[pos++] = pdu_id;
341     connection->cmd_operands[pos++] = 0;
342     // param length
343     big_endian_store_16(connection->cmd_operands, pos, 1);
344     pos += 2;
345     connection->cmd_operands[pos++] = event_id;
346     connection->cmd_operands_length = pos;
347 
348     connection->state = AVCTP_W2_SEND_RESPONSE;
349     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
350     return ERROR_CODE_SUCCESS;
351 }
352 
353 static uint8_t avrcp_target_response_vendor_dependent_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, uint8_t event_id, const uint8_t * value, uint16_t value_len){
354     connection->command_type = AVRCP_CTYPE_RESPONSE_INTERIM;
355     connection->subunit_type = subunit_type;
356     connection->subunit_id =   subunit_id;
357     connection->command_opcode = opcode;
358 
359     // company id is 3 bytes long
360     int pos = connection->cmd_operands_length;
361     connection->cmd_operands[pos++] = pdu_id;
362     connection->cmd_operands[pos++] = 0;
363     // param length
364     big_endian_store_16(connection->cmd_operands, pos, 1 + value_len);
365     pos += 2;
366     connection->cmd_operands[pos++] = event_id;
367     if (value && value_len > 0){
368         memcpy(connection->cmd_operands + pos, value, value_len);
369         pos += value_len;
370     }
371     connection->cmd_operands_length = pos;
372 
373     connection->state = AVCTP_W2_SEND_RESPONSE;
374     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
375     return ERROR_CODE_SUCCESS;
376 }
377 
378 // static uint8_t avrcp_target_response_vendor_dependent_changed(avrcp_connection_t * connection, avrcp_pdu_id_t pdu_id, uint8_t event_id){
379 //     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
380 //     connection->command_type = AVRCP_CTYPE_RESPONSE_CHANGED_STABLE;
381 //     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
382 //     connection->subunit_id = AVRCP_SUBUNIT_ID;
383 
384 //     // company id is 3 bytes long
385 //     int pos = connection->cmd_operands_length;
386 //     connection->cmd_operands[pos++] = pdu_id;
387 //     connection->cmd_operands[pos++] = 0;
388 //     // param length
389 //     big_endian_store_16(connection->cmd_operands, pos, 1);
390 //     pos += 2;
391 //     connection->cmd_operands[pos++] = event_id;
392 //     connection->cmd_operands_length = pos;
393 
394 //     connection->state = AVCTP_W2_SEND_RESPONSE;
395 //     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
396 //     return ERROR_CODE_SUCCESS;
397 // }
398 
399 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){
400     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
401     if (!connection){
402         log_error("avrcp_target_operation_reject: could not find a connection.");
403         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
404     }
405     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
406     // printf("avrcp_target_pass_through_response: operation 0x%02x, operands length %d\n", opid, operands_length);
407 
408     connection->command_type = cmd_type;
409     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
410     connection->subunit_id =   AVRCP_SUBUNIT_ID;
411     connection->command_opcode = AVRCP_CMD_OPCODE_PASS_THROUGH;
412 
413     int pos = 0;
414     connection->cmd_operands[pos++] = opid;
415     connection->cmd_operands[pos++] = operands_length;
416     if (operands_length == 1){
417         connection->cmd_operands[pos++] = operand;
418     }
419     connection->cmd_operands_length = pos;
420 
421     connection->state = AVCTP_W2_SEND_RESPONSE;
422     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
423     return ERROR_CODE_SUCCESS;
424 }
425 
426 uint8_t avrcp_target_operation_rejected(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
427     return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_REJECTED, opid, operands_length, operand);
428 }
429 
430 uint8_t avrcp_target_operation_accepted(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
431     return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_ACCEPTED, opid, operands_length, operand);
432 }
433 
434 uint8_t avrcp_target_operation_not_implemented(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
435     return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_ACCEPTED, opid, operands_length, operand);
436 }
437 
438 void avrcp_target_set_unit_info(uint16_t avrcp_cid, avrcp_subunit_type_t unit_type, uint32_t company_id){
439     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
440     if (!connection){
441         log_error("avrcp_target_operation_reject: could not find a connection.");
442         return;
443     }
444     connection->unit_type = unit_type;
445     connection->company_id = company_id;
446 }
447 
448 void 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){
449     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
450     if (!connection){
451         log_error("avrcp_target_operation_reject: could not find a connection.");
452         return;
453     }
454     connection->subunit_info_type = subunit_type;
455     connection->subunit_info_data = subunit_info_data;
456     connection->subunit_info_data_size = subunit_info_data_size;
457 }
458 
459 static uint8_t avrcp_target_unit_info(avrcp_connection_t * connection){
460     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
461 
462     uint8_t unit = 0;
463     connection->command_type = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
464     connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
465     connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
466     connection->command_opcode = AVRCP_CMD_OPCODE_UNIT_INFO;
467 
468     connection->cmd_operands_length = 5;
469     connection->cmd_operands[0] = 0x07;
470     connection->cmd_operands[1] = (connection->unit_type << 4) | unit;
471     // company id is 3 bytes long
472     big_endian_store_32(connection->cmd_operands, 2, connection->company_id);
473 
474     connection->state = AVCTP_W2_SEND_RESPONSE;
475     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
476     return ERROR_CODE_SUCCESS;
477 }
478 
479 static uint8_t avrcp_target_subunit_info(avrcp_connection_t * connection, uint8_t offset){
480     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
481     if (offset - 4 > connection->subunit_info_data_size) return AVRCP_STATUS_INVALID_PARAMETER;
482 
483     connection->command_opcode = AVRCP_CMD_OPCODE_SUBUNIT_INFO;
484     connection->command_type = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
485     connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
486     connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
487     // printf("avrcp_target_subunit_info  subunit_type %d\n", connection->subunit_type);
488 
489     uint8_t page = offset / 4;
490     uint8_t extension_code = 7;
491     connection->cmd_operands_length = 5;
492     connection->cmd_operands[0] = (page << 4) | extension_code;
493 
494     memcpy(connection->cmd_operands+1, connection->subunit_info_data + offset, 4);
495 
496     connection->state = AVCTP_W2_SEND_RESPONSE;
497     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
498     return ERROR_CODE_SUCCESS;
499 }
500 
501 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){
502     *out_connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
503     if (!*out_connection){
504         log_error("avrcp tartget: could not find a connection.");
505         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
506     }
507 
508     if ((*out_connection)->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
509     (*out_connection)->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
510     (*out_connection)->command_type    = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
511     (*out_connection)->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
512     (*out_connection)->subunit_id      = AVRCP_SUBUNIT_ID;
513 
514     (*out_connection)->cmd_operands[(*out_connection)->cmd_operands_length++] = pdu_id;
515     // reserved
516     (*out_connection)->cmd_operands[(*out_connection)->cmd_operands_length++] = 0;
517     // param length
518     big_endian_store_16((*out_connection)->cmd_operands, (*out_connection)->cmd_operands_length, param_length);
519     (*out_connection)->cmd_operands_length += 2;
520     return ERROR_CODE_SUCCESS;
521 }
522 
523 static uint8_t avrcp_target_capability(uint16_t avrcp_cid, avrcp_capability_id_t capability_id, uint8_t capabilities_num, uint8_t * capabilities, uint8_t size){
524     avrcp_connection_t * connection = NULL;
525     uint8_t status = avrcp_prepare_vendor_dependent_response(avrcp_cid, &connection, AVRCP_PDU_ID_GET_CAPABILITIES, 2+size);
526     if (status != ERROR_CODE_SUCCESS) return status;
527 
528     connection->cmd_operands[connection->cmd_operands_length++] = capability_id;
529     connection->cmd_operands[connection->cmd_operands_length++] = capabilities_num;
530     memcpy(connection->cmd_operands+connection->cmd_operands_length, capabilities, size);
531     connection->cmd_operands_length += size;
532 
533     connection->state = AVCTP_W2_SEND_RESPONSE;
534     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
535     return ERROR_CODE_SUCCESS;
536 }
537 
538 uint8_t avrcp_target_supported_events(uint16_t avrcp_cid, uint8_t capabilities_num, uint8_t * capabilities, uint8_t size){
539     return avrcp_target_capability(avrcp_cid, AVRCP_CAPABILITY_ID_EVENT, capabilities_num, capabilities, size);
540 }
541 
542 uint8_t avrcp_target_supported_companies(uint16_t avrcp_cid, uint8_t capabilities_num, uint8_t * capabilities, uint8_t size ){
543     return avrcp_target_capability(avrcp_cid, AVRCP_CAPABILITY_ID_COMPANY, capabilities_num, capabilities, size);
544 }
545 
546 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){
547     avrcp_connection_t * connection = NULL;
548     uint8_t status = avrcp_prepare_vendor_dependent_response(avrcp_cid, &connection, AVRCP_PDU_ID_GET_PLAY_STATUS, 11);
549     if (status != ERROR_CODE_SUCCESS) return status;
550 
551     big_endian_store_32(connection->cmd_operands, connection->cmd_operands_length, song_length_ms);
552     connection->cmd_operands_length += 4;
553     big_endian_store_32(connection->cmd_operands, connection->cmd_operands_length, song_position_ms);
554     connection->cmd_operands_length += 4;
555     connection->cmd_operands[connection->cmd_operands_length++] = play_status;
556 
557     connection->state = AVCTP_W2_SEND_RESPONSE;
558     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
559     return ERROR_CODE_SUCCESS;
560 }
561 
562 static uint8_t avrcp_target_now_playing_info(avrcp_connection_t * connection){
563     connection->now_playing_info_response = 1;
564     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
565     connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
566     connection->command_type    = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
567     connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
568     connection->subunit_id      = AVRCP_SUBUNIT_ID;
569 
570     connection->state = AVCTP_W2_SEND_RESPONSE;
571     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
572     return ERROR_CODE_SUCCESS;
573 }
574 
575 static uint8_t avrcp_target_store_media_attr(avrcp_connection_t * connection, avrcp_media_attribute_id_t attr_id, const char * value){
576     int index = attr_id - 1;
577     if (!value) return AVRCP_STATUS_INVALID_PARAMETER;
578     connection->now_playing_info[index].value = (uint8_t*)value;
579     connection->now_playing_info[index].len   = strlen(value);
580     // printf("store %lu bytes, %s\n",  strlen(value), value);
581     return ERROR_CODE_SUCCESS;
582 }
583 
584 uint8_t avrcp_target_set_playback_status(uint16_t avrcp_cid, avrcp_playback_status_t playback_status){
585     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
586     if (!connection){
587         log_error("avrcp_unit_info: could not find a connection.");
588         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
589     }
590     if (connection->playback_status == playback_status) return ERROR_CODE_SUCCESS;
591 
592     connection->playback_status = playback_status;
593     connection->playback_status_changed = 1;
594     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
595     return ERROR_CODE_SUCCESS;
596 }
597 
598 void avrcp_target_set_now_playing_info(uint16_t avrcp_cid, const avrcp_track_t * current_track, uint16_t total_tracks){
599     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
600     if (!connection){
601         log_error("avrcp_unit_info: could not find a connection. cid 0x%02x\n", avrcp_cid);
602         return;
603     }
604     if (!current_track){
605         connection->track_selected = 0;
606         connection->playback_status = AVRCP_PLAYBACK_STATUS_ERROR;
607         return;
608     }
609     memcpy(connection->track_id, current_track->track_id, 8);
610     connection->song_length_ms = current_track->song_length_ms;
611     connection->track_nr = current_track->track_nr;
612     connection->total_tracks = total_tracks;
613     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_TITLE, current_track->title);
614     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_ARTIST, current_track->artist);
615     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_ALBUM, current_track->album);
616     avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_GENRE, current_track->genre);
617     connection->track_selected = 1;
618 
619     if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED)) {
620         connection->track_changed = 1;
621         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
622     }
623     return;
624 }
625 
626 uint8_t avrcp_target_playing_content_changed(uint16_t avrcp_cid){
627     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
628     if (!connection){
629         log_error("avrcp_unit_info: could not find a connection.");
630         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
631     }
632     connection->playing_content_changed = 1;
633     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
634     return ERROR_CODE_SUCCESS;
635 }
636 
637 uint8_t avrcp_target_battery_status_changed(uint16_t avrcp_cid, avrcp_battery_status_t battery_status){
638     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
639     if (!connection){
640         log_error("avrcp_unit_info: could not find a connection.");
641         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
642     }
643     if (connection->battery_status == battery_status) return ERROR_CODE_SUCCESS;
644     connection->battery_status = battery_status;
645     connection->battery_status_changed = 1;
646     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
647     return ERROR_CODE_SUCCESS;
648 }
649 
650 uint8_t avrcp_target_volume_changed(uint16_t avrcp_cid, uint8_t volume_percentage){
651         avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
652     if (!connection){
653         log_error("avrcp_unit_info: could not find a connection.");
654         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
655     }
656     if (connection->volume_percentage == volume_percentage) return ERROR_CODE_SUCCESS;
657 
658     connection->volume_percentage = volume_percentage;
659     connection->volume_percentage_changed = 1;
660     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
661     return ERROR_CODE_SUCCESS;
662 }
663 
664 
665 static uint8_t * avrcp_get_company_id(uint8_t *packet, uint16_t size){
666     UNUSED(size);
667     return packet + 6;
668 }
669 
670 static uint8_t * avrcp_get_pdu(uint8_t *packet, uint16_t size){
671     UNUSED(size);
672     return packet + 9;
673 }
674 
675 static uint8_t avrcp_is_receive_pass_through_cmd(uint8_t operation_id){
676     return operation_id & 0x80;
677 }
678 
679 static void avrcp_handle_l2cap_data_packet_for_signaling_connection(avrcp_connection_t * connection, uint8_t *packet, uint16_t size){
680     UNUSED(connection);
681     UNUSED(packet);
682     UNUSED(size);
683 
684     // uint8_t opcode;
685 
686     uint8_t transport_header = packet[0];
687     connection->transaction_label = transport_header >> 4;
688     // uint8_t packet_type = (transport_header & 0x0F) >> 2;
689     // uint8_t frame_type = (transport_header & 0x03) >> 1;
690     // uint8_t ipid = transport_header & 0x01;
691     // uint8_t byte_value = packet[2];
692     // uint16_t pid = (byte_value << 8) | packet[2];
693 
694     // avrcp_command_type_t ctype = (avrcp_command_type_t) packet[3];
695     // uint8_t byte_value = packet[4];
696     avrcp_subunit_type_t subunit_type = (avrcp_subunit_type_t) (packet[4] >> 3);
697     avrcp_subunit_id_t   subunit_id   = (avrcp_subunit_id_t) (packet[4] & 0x07);
698     // opcode = packet[pos++];
699 
700     // printf("    Transport header 0x%02x (transaction_label %d, packet_type %d, frame_type %d, ipid %d), pid 0x%4x\n",
701     //     transport_header, transaction_label, packet_type, frame_type, ipid, pid);
702     // printf_hexdump(packet+pos, size-pos);
703 
704     avrcp_command_opcode_t opcode = avrcp_cmd_opcode(packet,size);
705     uint8_t * company_id = avrcp_get_company_id(packet, size);
706     uint8_t * pdu = avrcp_get_pdu(packet, size);
707     // uint16_t param_length = big_endian_read_16(pdu, 2);
708 
709     int pos = 4;
710     uint8_t   pdu_id;
711     connection->cmd_operands_length = 0;
712 
713     switch (opcode){
714         case AVRCP_CMD_OPCODE_UNIT_INFO:
715             avrcp_target_unit_info(connection);
716             break;
717         case AVRCP_CMD_OPCODE_SUBUNIT_INFO:{
718             uint8_t offset =  4 * (packet[pos+2]>>4);
719             avrcp_target_subunit_info(connection, offset);
720             break;
721         }
722         case AVRCP_CMD_OPCODE_PASS_THROUGH:{
723             log_info("AVRCP_OPERATION_ID 0x%02x, operands length %d, operand %d", packet[6], packet[7], packet[8]);
724             avrcp_operation_id_t operation_id = packet[6];
725 
726             if (avrcp_is_receive_pass_through_cmd(operation_id)){
727                 operation_id = packet[6] & 0x7F;
728             }
729 
730             switch (operation_id){
731                 case AVRCP_OPERATION_ID_PLAY:
732                 case AVRCP_OPERATION_ID_PAUSE:
733                 case AVRCP_OPERATION_ID_STOP:
734                     avrcp_target_operation_accepted(connection->avrcp_cid, packet[6], packet[7], packet[8]);
735                     avrcp_target_emit_operation(avrcp_target_context.avrcp_callback, connection->avrcp_cid, packet[6], packet[7], packet[8]);
736                     break;
737                 case AVRCP_OPERATION_ID_REWIND:
738                 case AVRCP_OPERATION_ID_FAST_FORWARD:
739                 case AVRCP_OPERATION_ID_FORWARD:
740                 case AVRCP_OPERATION_ID_BACKWARD:
741                 case AVRCP_OPERATION_ID_SKIP:
742                 case AVRCP_OPERATION_ID_VOLUME_UP:
743                 case AVRCP_OPERATION_ID_VOLUME_DOWN:
744                 case AVRCP_OPERATION_ID_MUTE:
745                 case AVRCP_OPERATION_ID_UNDEFINED:
746                     avrcp_target_operation_not_implemented(connection->avrcp_cid, packet[6], packet[7], packet[8]);
747                     return;
748                 default:
749                     avrcp_target_operation_not_implemented(connection->avrcp_cid, packet[6], packet[7], packet[8]);
750                     break;
751             }
752             break;
753         }
754 
755         case AVRCP_CMD_OPCODE_VENDOR_DEPENDENT:
756             pdu_id = pdu[0];
757             // 1 - reserved
758             // 2-3 param length,
759             memcpy(connection->cmd_operands, company_id, 3);
760             connection->cmd_operands_length = 3;
761             switch (pdu_id){
762                 case AVRCP_PDU_ID_GET_CAPABILITIES:{
763                     avrcp_capability_id_t capability_id = (avrcp_capability_id_t) pdu[pos];
764                     switch (capability_id){
765                         case AVRCP_CAPABILITY_ID_EVENT:
766                             avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_EVENT_IDS_QUERY);
767                             break;
768                         case AVRCP_CAPABILITY_ID_COMPANY:
769                             avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_COMPANY_IDS_QUERY);
770                             break;
771                         default:
772                             avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
773                             break;
774                     }
775                     break;
776                 }
777                 case AVRCP_PDU_ID_GET_PLAY_STATUS:
778                     avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_PLAY_STATUS_QUERY);
779                     break;
780                 case AVRCP_PDU_ID_REQUEST_ABORT_CONTINUING_RESPONSE:
781                     connection->cmd_operands[0] = pdu[4];
782                     connection->abort_continue_response = 1;
783                     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
784                     break;
785                 case AVRCP_PDU_ID_REQUEST_CONTINUING_RESPONSE:
786                     if (pdu[4] != AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES){
787                         avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
788                         return;
789                     }
790                     connection->now_playing_info_response = 1;
791                     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
792                     break;
793                 case AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES:{
794                     uint8_t play_identifier[8];
795                     memset(play_identifier, 0, 8);
796                     if (memcmp(pdu+pos, play_identifier, 8) != 0) {
797                         avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
798                         return;
799                     }
800                     pos += 8;
801                     uint8_t attribute_count = pdu[pos++];
802                     // printf("AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES attribute count %d\n", attribute_count);
803                     connection->next_attr_id = AVRCP_MEDIA_ATTR_NONE;
804                     if (!attribute_count){
805                         connection->now_playing_info_attr_bitmap = 0xFE;
806                     } else {
807                         int i;
808                         connection->now_playing_info_attr_bitmap = 0;
809                         for (i=0; i < attribute_count; i++){
810                             uint16_t attr_id = big_endian_read_16(pdu, pos);
811                             pos += 2;
812                             connection->now_playing_info_attr_bitmap |= (1 << attr_id);
813                         }
814                     }
815                     log_info("now_playing_info_attr_bitmap 0x%02x", connection->now_playing_info_attr_bitmap);
816                     avrcp_target_now_playing_info(connection);
817                     break;
818                 }
819                 case AVRCP_PDU_ID_REGISTER_NOTIFICATION:{
820                     // 0 - pdu id
821                     // 1 - reserved
822                     // 2-3 param length
823                     avrcp_notification_event_id_t event_id = (avrcp_notification_event_id_t) pdu[4];
824                     uint16_t event_mask = (1 << event_id);
825 
826                     switch (event_id){
827                         case AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED:
828                             connection->notifications_enabled |= event_mask;
829                             if (connection->track_selected){
830                                 avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, AVRCP_NOTIFICATION_TRACK_SELECTED, 8);
831                             } else {
832                                 avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, AVRCP_NOTIFICATION_TRACK_NOT_SELECTED, 8);
833                             }
834                             break;
835                         case AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED:
836                             connection->notifications_enabled |= event_mask;
837                             avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, (const uint8_t *)&connection->playback_status, 1);
838                             break;
839                         case AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED:
840                             connection->notifications_enabled |= event_mask;
841                             avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, NULL, 0);
842                             break;
843                         case AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED:
844                             connection->notifications_enabled |= event_mask;
845                             avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, (const uint8_t *)&connection->volume_percentage, 1);
846                             break;
847                         case AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED:
848                             connection->notifications_enabled |= event_mask;
849                             avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, (const uint8_t *)&connection->battery_status, 1);
850                             break;
851                         case AVRCP_NOTIFICATION_EVENT_AVAILABLE_PLAYERS_CHANGED:
852                         case AVRCP_NOTIFICATION_EVENT_PLAYER_APPLICATION_SETTING_CHANGED:
853                         case AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED:
854                         case AVRCP_NOTIFICATION_EVENT_UIDS_CHANGED:
855                             avrcp_target_response_not_implemented(connection, subunit_type, subunit_id, opcode, pdu_id, event_id);
856                             return;
857                         default:
858                             avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
859                             return;
860                     }
861                     break;
862                 }
863                 default:
864                     log_info("AVRCP target: unhandled pdu id 0x%02x", pdu_id);
865                     avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
866                     break;
867             }
868             break;
869         default:
870             log_info("AVRCP target: opcode 0x%02x not implemented", avrcp_cmd_opcode(packet,size));
871             break;
872     }
873 }
874 
875 static int avrcp_target_send_notification(uint16_t cid, avrcp_connection_t * connection, uint8_t notification_id, uint8_t * value, uint16_t value_len){
876     if (!connection){
877         log_error("avrcp tartget: could not find a connection.");
878         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
879     }
880 
881     connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
882     connection->command_type    = AVRCP_CTYPE_RESPONSE_CHANGED_STABLE;
883     connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
884     connection->subunit_id      = AVRCP_SUBUNIT_ID;
885 
886     uint16_t pos = 0;
887     l2cap_reserve_packet_buffer();
888     uint8_t * packet = l2cap_get_outgoing_buffer();
889     uint16_t  size   = l2cap_get_remote_mtu_for_local_cid(connection->l2cap_signaling_cid);
890 
891     connection->packet_type = AVRCP_SINGLE_PACKET;
892     packet[pos++] = (connection->transaction_label << 4) | (connection->packet_type << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
893     // Profile IDentifier (PID)
894     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
895     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
896 
897     // command_type
898     packet[pos++] = connection->command_type;
899     // subunit_type | subunit ID
900     packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
901     // opcode
902     packet[pos++] = (uint8_t)connection->command_opcode;
903 
904     // company id is 3 bytes long
905     big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
906     pos += 3;
907 
908     packet[pos++] = AVRCP_PDU_ID_REGISTER_NOTIFICATION;
909     packet[pos++] = 0;
910     uint16_t remainig_outgoing_buffer_size = size > (value_len + 2 + 1) ? size - (value_len + 2 + 1): 0;
911     uint16_t caped_value_len = value_len > remainig_outgoing_buffer_size ? remainig_outgoing_buffer_size : value_len;
912     big_endian_store_16(packet, pos, caped_value_len);
913     pos += 2;
914     packet[pos++] = notification_id;
915 
916     memcpy(packet+pos, value, caped_value_len);
917     pos += caped_value_len;
918     connection->wait_to_send = 0;
919     return l2cap_send_prepared(cid, pos);
920 }
921 
922 static void avrcp_controller_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
923     avrcp_connection_t * connection;
924     switch (packet_type) {
925         case L2CAP_DATA_PACKET:
926             connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, &avrcp_target_context);
927             if (!connection) break;
928             avrcp_handle_l2cap_data_packet_for_signaling_connection(connection, packet, size);
929             break;
930         case HCI_EVENT_PACKET:
931             switch (hci_event_packet_get_type(packet)){
932                 case L2CAP_EVENT_CAN_SEND_NOW:{
933                     connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, &avrcp_target_context);
934                     if (!connection) break;
935 
936                     if (connection->abort_continue_response){
937                         connection->abort_continue_response = 0;
938                         connection->now_playing_info_response = 0;
939                         avrcp_target_abort_continue_response(connection->l2cap_signaling_cid, connection);
940                     }
941 
942                     if (connection->now_playing_info_response){
943                         connection->now_playing_info_response = 0;
944                         avrcp_target_send_now_playing_info(connection->l2cap_signaling_cid, connection);
945                         break;
946                     }
947                     break;
948 
949                     if (connection->track_changed){
950                         connection->track_changed = 0;
951                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED, connection->track_id, 8);
952                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
953                         break;
954                     }
955 
956                     if (connection->playback_status_changed){
957                         connection->playback_status_changed = 0;
958                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED, &connection->playback_status_changed, 1);
959                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
960                         break;
961                     }
962 
963                     if (connection->playing_content_changed){
964                         connection->playing_content_changed = 0;
965                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED, NULL, 0);
966                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
967                         break;
968                     }
969 
970                     if (connection->battery_status_changed){
971                         connection->battery_status_changed = 0;
972                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED, (uint8_t *)&connection->battery_status, 1);
973                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
974                         break;
975                     }
976 
977                     if (connection->volume_percentage_changed){
978                         connection->volume_percentage_changed = 0;
979                         avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED, &connection->volume_percentage, 1);
980                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
981                         break;
982                     }
983 
984                     switch (connection->state){
985                         case AVCTP_W2_SEND_RESPONSE:
986                             connection->state = AVCTP_CONNECTION_OPENED;
987                             // if (connection->now_playing_info_response){
988                             //     connection->now_playing_info_response = 0;
989                             //     avrcp_target_send_now_playing_info(connection->l2cap_signaling_cid, connection);
990                             //     break;
991                             // }
992                             avrcp_target_send_response(connection->l2cap_signaling_cid, connection);
993                             break;
994                         default:
995                             return;
996                     }
997                     break;
998             }
999             default:
1000                 avrcp_packet_handler(packet_type, channel, packet, size, &avrcp_target_context);
1001                 break;
1002         }
1003         default:
1004             break;
1005     }
1006 }
1007 
1008 void avrcp_target_init(void){
1009     avrcp_target_context.role = AVRCP_TARGET;
1010     avrcp_target_context.connections = NULL;
1011     avrcp_target_context.packet_handler = avrcp_controller_packet_handler;
1012     l2cap_register_service(&avrcp_controller_packet_handler, BLUETOOTH_PROTOCOL_AVCTP, 0xffff, LEVEL_0);
1013 }
1014 
1015 void avrcp_target_register_packet_handler(btstack_packet_handler_t callback){
1016     if (callback == NULL){
1017         log_error("avrcp_register_packet_handler called with NULL callback");
1018         return;
1019     }
1020     avrcp_target_context.avrcp_callback = callback;
1021 }
1022 
1023 uint8_t avrcp_target_connect(bd_addr_t bd_addr, uint16_t * avrcp_cid){
1024     return avrcp_connect(bd_addr, &avrcp_target_context, avrcp_cid);
1025 }
1026 
1027 uint8_t avrcp_target_disconnect(uint16_t avrcp_cid){
1028     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
1029     if (!connection){
1030         log_error("avrcp_get_capabilities: could not find a connection.");
1031         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1032     }
1033     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1034     l2cap_disconnect(connection->l2cap_signaling_cid, 0);
1035     return ERROR_CODE_SUCCESS;
1036 }
1037 
1038