feat: Add support for switching to previously used bluetooth profile

app/include/dt-bindings/zmk/bt.h

@@ -7,9 +7,10 @@
 #define BT_CLR_CMD 0
 #define BT_NXT_CMD 1
 #define BT_PRV_CMD 2
-#define BT_SEL_CMD 3
-#define BT_CLR_ALL_CMD 4
-#define BT_DISC_CMD 5
+#define BT_PRV_DEV_CMD 3
+#define BT_SEL_CMD 4
+#define BT_CLR_ALL_CMD 5
+#define BT_DISC_CMD 6
 
 /*
 Note: Some future commands will include additional parameters, so we
@@ -19,6 +20,7 @@ defines these aliases up front.
 #define BT_CLR BT_CLR_CMD 0
 #define BT_NXT BT_NXT_CMD 0
 #define BT_PRV BT_PRV_CMD 0
+#define BT_PRV_DEV BT_PRV_DEV_CMD 0
 #define BT_SEL BT_SEL_CMD
 #define BT_CLR_ALL BT_CLR_ALL_CMD 0
 #define BT_DISC BT_DISC_CMD

app/include/zmk/ble.h

@@ -23,6 +23,7 @@
 void zmk_ble_clear_bonds(void);
 int zmk_ble_prof_next(void);
 int zmk_ble_prof_prev(void);
+int zmk_ble_prof_prev_dev(void);
 int zmk_ble_prof_select(uint8_t index);
 void zmk_ble_clear_all_bonds(void);
 int zmk_ble_prof_disconnect(uint8_t index);

app/src/behaviors/behavior_bt.c

@@ -33,6 +33,11 @@ static const struct behavior_parameter_value_metadata no_arg_values[] = {
         .type = BEHAVIOR_PARAMETER_VALUE_TYPE_VALUE,
         .value = BT_PRV_CMD,
     },
+    {
+        .display_name = "Previously Used Profile",
+        .type = BEHAVIOR_PARAMETER_VALUE_TYPE_VALUE,
+        .value = BT_PRV_DEV_CMD,
+    },
     {
         .display_name = "Clear All Profiles",
         .type = BEHAVIOR_PARAMETER_VALUE_TYPE_VALUE,
@@ -98,6 +103,8 @@ static int on_keymap_binding_pressed(struct zmk_behavior_binding *binding,
         return zmk_ble_prof_next();
     case BT_PRV_CMD:
         return zmk_ble_prof_prev();
+    case BT_PRV_DEV_CMD:
+        return zmk_ble_prof_prev_dev();
     case BT_SEL_CMD:
         return zmk_ble_prof_select(binding->param2);
     case BT_CLR_ALL_CMD:

app/src/ble.c

@@ -61,6 +61,7 @@ enum advertising_type {
 
 static struct zmk_ble_profile profiles[ZMK_BLE_PROFILE_COUNT];
 static uint8_t active_profile;
+static uint8_t previous_profile = 0;
 
 #define DEVICE_NAME CONFIG_BT_DEVICE_NAME
 #define DEVICE_NAME_LEN (sizeof(DEVICE_NAME) - 1)
@@ -274,6 +275,7 @@ int zmk_ble_prof_select(uint8_t index) {
         return 0;
     }
 
+    previous_profile = active_profile;
     active_profile = index;
     ble_save_profile();
 
@@ -295,6 +297,11 @@ int zmk_ble_prof_prev(void) {
                                ZMK_BLE_PROFILE_COUNT);
 };
 
+int zmk_ble_prof_prev_dev(void) {
+    LOG_DBG("");
+    return zmk_ble_prof_select(previous_profile);
+};
+
 int zmk_ble_prof_disconnect(uint8_t index) {
     if (index >= ZMK_BLE_PROFILE_COUNT)
         return -ERANGE;

docs/docs/keymaps/behaviors/bluetooth.md

@@ -44,11 +44,12 @@ Here is a table describing the command for each define:
 | `BT_CLR_ALL` | Clear bond information between the keyboard and host for all profiles.                                                                                                             |
 | `BT_NXT`     | Switch to the next profile, cycling through to the first one when the end is reached.                                                                                              |
 | `BT_PRV`     | Switch to the previous profile, cycling through to the last one when the beginning is reached.                                                                                     |
+| `BT_PRV_DEV` | Switch to the previously used profile.                                                                                                                                             |
 | `BT_SEL`     | Select the 0-indexed profile by number; must include a number as an argument in the keymap to work correctly, e.g. `BT_SEL 0`.                                                     |
 | `BT_DISC`    | Disconnect from the 0-indexed profile by number, if it's currently connected and inactive; must include a number as an argument in the keymap to work correctly, e.g. `BT_DISC 0`. |
 
 :::note[Selected profile persistence]
-The profile that is selected by the `BT_SEL`/`BT_PRV`/`BT_NXT` actions will be saved to flash storage and hence persist across restarts and firmware flashes.
+The profile that is selected by the `BT_SEL`/`BT_PRV`/`BT_PRV_DEV`/`BT_NXT` actions will be saved to flash storage and hence persist across restarts and firmware flashes.
 However it will only be saved after [`CONFIG_ZMK_SETTINGS_SAVE_DEBOUNCE`](../../config/system.md#general) milliseconds in order to reduce potential wear on the flash memory.
 :::
 
@@ -82,6 +83,12 @@ The bluetooth behavior completes an bluetooth action given on press.
    &bt BT_PRV
    ```
 
+1. Behavior binding to select the previously used profile:
+
+   ```dts
+   &bt BT_PRV_DEV
+   ```
+
 1. Behavior binding to select the 2nd profile (passed parameters are [zero based](https://en.wikipedia.org/wiki/Zero-based_numbering)):
 
    ```dts