Bluetooth: Classic: HFP: AG: Add vendor at cmd API and callback.

bug: v/79377

Rootcause: Add vendor_at_cmd callback and bt_hfp_ag_send_vendor API  to recieve and send vendor-specific AT commands.

Signed-off-by: liyuheng [email protected]

Author: expliyh

include/zephyr/bluetooth/classic/hfp_ag.h

@@ -460,6 +460,35 @@ struct bt_hfp_ag_cb {
 	 */
 	void (*hf_indicator_value)(struct bt_hfp_ag *ag, enum hfp_ag_hf_indicators indicator,
 				   uint32_t value);
+
+	/** Vendor specific / custom AT command callback
+	 *
+	 *  If this callback is provided it will be called whenever an AT command
+	 *  is received from the HF that is not recognized and handled by the
+	 *  HFP AG stack.
+	 *
+	 *  The @p cmd string contains the full AT command line as received on
+	 *  the RFCOMM link, without the terminating carriage return character.
+	 *  Example: "AT+XMI=1,2".
+	 *
+	 *  The return value controls how the HFP AG core replies:
+	 *  - ret < 0 : The command is rejected and the core will send the
+	 *              standard "ERROR" or "+CME ERROR:<code>" depending on
+	 *              the CMEE setting.
+	 *  - ret == 0: The command was handled successfully and the core will
+	 *              send the standard "OK" final result code.
+	 *  - ret > 0 : The application is responsible for sending all responses,
+	 *              including the final "OK" / "ERROR" / "+CME ERROR:<code>",
+	 *              by calling @ref bt_hfp_ag_send_vendor from an appropriate
+	 *              context. The HFP AG core will NOT send any automatic
+	 *              final result code in this case.
+	 *
+	 *  @param ag HFP AG object.
+	 *  @param cmd Zero-terminated AT command line without trailing <CR>.
+	 *
+	 *  @return Application-defined result as described above.
+	 */
+	int (*vendor_at_cmd)(struct bt_hfp_ag *ag, const char *cmd);
 };
 
 /** @brief Register HFP AG profile
@@ -819,6 +848,26 @@ int Z_API(bt_hfp_ag_battery_level)(struct bt_hfp_ag *ag, uint8_t level);
  */
 int Z_API(bt_hfp_ag_service_availability)(struct bt_hfp_ag *ag, bool available);
 
+/** @brief Send vendor specific / custom AT response from the AG
+ *
+ *  Send a vendor specific or otherwise custom AT result or unsolicited
+ *  response line from the AG to the HF.
+ *  The given string is sent as-is and will be wrapped with the standard
+ *  "\r\n" prefix and suffix on the wire.
+ *
+ *  Examples (rsp non-NULL): 
+ *  - rsp == NULL        -> sends a standard final result "OK"
+ *                          (i.e. "\r\nOK\r\n").
+ *  - rsp = "+CUSTOM:0"  -> sends "\r\n+CUSTOM:0\r\n"
+ *  - rsp = "+VENDOR:1"  -> sends "\r\n+VENDOR:1\r\n"
+ *
+ *  @param ag HFP AG object.
+ *  @param rsp AT response string without CR/LF terminators, or NULL to send "OK".
+ *
+ *  @return 0 in case of success or negative value in case of error.
+ */
+int Z_API(bt_hfp_ag_send_vendor)(struct bt_hfp_ag *ag, const char *rsp);
+
 /** @brief Activate/deactivate HF indicator
  *
  *  It allows HF to issue the +BIND unsolicited result code to

subsys/bluetooth/host/classic/hfp_ag.c

@@ -3523,6 +3523,23 @@ static void hfp_ag_recv(struct bt_rfcomm_dlc *dlc, struct net_buf *buf)
 		}
 	}
 
+	if ((err == -ENOEXEC) && bt_ag && bt_ag->vendor_at_cmd) {
+		size_t copy_len;
+
+		copy_len = MIN(len, sizeof(ag->buffer) - 1);
+		memcpy(ag->buffer, data, copy_len);
+		ag->buffer[copy_len] = '\0';
+
+		if ((copy_len > 0) && (ag->buffer[copy_len - 1] == '\r')) {
+			ag->buffer[copy_len - 1] = '\0';
+		}
+
+		err = bt_ag->vendor_at_cmd(ag, ag->buffer);
+		if (err > 0) {
+			return;
+		}
+	}
+
 	if (err == -EINPROGRESS) {
 		LOG_DBG("OK code will be replied later");
 		return;
@@ -5212,6 +5229,34 @@ int Z_API(bt_hfp_ag_service_availability)(struct bt_hfp_ag *ag, bool available)
 	return err;
 }
 
+int Z_API(bt_hfp_ag_send_vendor)(struct bt_hfp_ag *ag, const char *rsp)
+{
+	int err;
+	const char *line;
+
+	LOG_DBG("");
+
+	if (ag == NULL) {
+		return -EINVAL;
+	}
+
+	hfp_ag_lock(ag);
+	if (ag->state != BT_HFP_CONNECTED) {
+		hfp_ag_unlock(ag);
+		return -ENOTCONN;
+	}
+	hfp_ag_unlock(ag);
+
+	line = (rsp == NULL) ? "OK" : rsp;
+
+	err = hfp_ag_send_data(ag, NULL, NULL, "\r\n%s\r\n", line);
+	if (err) {
+		LOG_ERR("Fail to send vendor specific response (%d)", err);
+	}
+
+	return err;
+}
+
 int Z_API(bt_hfp_ag_hf_indicator)(struct bt_hfp_ag *ag, enum hfp_ag_hf_indicators indicator, bool enable)
 {
 #if defined(CONFIG_BT_HFP_AG_HF_INDICATORS)