feat(studio): Add new keymap subsystem.

* Add APIs for fetching the current keymap, and updating a particular
  binding in a layer of the keymap, including validation of parameters.
* Add API for savings/discarding keymap changes.

app/proto/zmk/keymap.proto

@@ -4,6 +4,47 @@ package zmk.keymap;
 
 message Request {
     oneof request_type {
-        bool get_layer_summaries = 1;
+        bool get_keymap = 1;
+        SetLayerBindingRequest set_layer_binding = 2;
+        bool save_changes = 3;
+        bool discard_changes = 4;
     }
+}
+
+message Response {
+    oneof response_type {
+        Keymap get_keymap = 1;
+        SetLayerBindingResponse set_layer_binding = 2;
+        bool save_changes = 3;
+        bool discard_changes = 4;
+    }
+}
+
+enum SetLayerBindingResponse {
+    SUCCESS = 0;
+    INVALID_LOCATION = 1;
+    INVALID_BEHAVIOR = 2;
+    INVALID_PARAMETERS = 3;
+}
+
+message SetLayerBindingRequest {
+    int32 layer = 1;
+    int32 key_position = 2;
+
+    BehaviorBinding binding = 3;
+}
+
+message Keymap {
+    repeated Layer layers = 1;
+}
+
+message Layer {
+    string name = 1;
+    repeated BehaviorBinding bindings = 2;
+}
+
+message BehaviorBinding {
+    sint32 behavior_id = 1;
+    uint32 param1 = 2;
+    uint32 param2 = 3;
 }

app/proto/zmk/studio.proto

@@ -12,9 +12,9 @@ message Request {
     uint32 request_id = 1;
 
     oneof subsystem {
-        zmk.core.Request core = 2;
-        zmk.keymap.Request keymap = 3;
+        zmk.core.Request core = 3;
         zmk.behaviors.Request behaviors = 4;
+        zmk.keymap.Request keymap = 5;
     }
 }
 
@@ -31,6 +31,7 @@ message RequestResponse {
         zmk.meta.Response meta = 2;
         zmk.core.Response core = 3;
         zmk.behaviors.Response behaviors = 4;
+        zmk.keymap.Response keymap = 5;
     }
 }
 

app/src/studio/CMakeLists.txt

@@ -11,5 +11,6 @@ target_sources(app PRIVATE rpc.c)
 target_sources(app PRIVATE core.c)
 target_sources(app PRIVATE behavior_subsystem.c)
 target_sources(app PRIVATE core_subsystem.c)
+target_sources(app PRIVATE keymap_subsystem.c)
 target_sources_ifdef(CONFIG_ZMK_STUDIO_TRANSPORT_UART app PRIVATE uart_rpc_transport.c)
 target_sources_ifdef(CONFIG_ZMK_STUDIO_TRANSPORT_BLE app PRIVATE gatt_rpc_transport.c)

app/src/studio/Kconfig

@@ -9,6 +9,7 @@ menuconfig ZMK_STUDIO
     imply  NANOPB_WITHOUT_64BIT
     select ZMK_BEHAVIOR_METADATA
     select ZMK_BEHAVIOR_LOCAL_IDS
+    select ZMK_KEYMAP_SETTINGS_STORAGE
     help
       Add firmware support for realtime keymap updates (ZMK Studio
 

app/src/studio/keymap_subsystem.c

@@ -0,0 +1,164 @@
+/*
+ * Copyright (c) 2024 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/logging/log.h>
+
+LOG_MODULE_DECLARE(zmk_studio, CONFIG_ZMK_STUDIO_LOG_LEVEL);
+
+#include <drivers/behavior.h>
+
+#include <zmk/behavior.h>
+#include <zmk/matrix.h>
+#include <zmk/keymap.h>
+#include <zmk/studio/rpc.h>
+
+#include <pb_encode.h>
+
+ZMK_RPC_SUBSYSTEM(keymap)
+
+#define KEYMAP_RESPONSE(type, ...) ZMK_RPC_RESPONSE(keymap, type, __VA_ARGS__)
+
+static bool encode_layer_bindings(pb_ostream_t *stream, const pb_field_t *field, void *const *arg) {
+    const uint8_t layer_idx = *(uint8_t *)*arg;
+
+    for (int b = 0; b < ZMK_KEYMAP_LEN; b++) {
+        const struct zmk_behavior_binding *binding =
+            zmk_keymap_get_layer_binding_at_idx(layer_idx, b);
+
+        zmk_keymap_BehaviorBinding bb = zmk_keymap_BehaviorBinding_init_zero;
+
+        bb.behavior_id = zmk_behavior_get_local_id(binding->behavior_dev);
+        bb.param1 = binding->param1;
+        bb.param2 = binding->param2;
+
+        if (!pb_encode_tag_for_field(stream, field)) {
+            return false;
+        }
+
+        if (!pb_encode_submessage(stream, &zmk_keymap_BehaviorBinding_msg, &bb)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static bool encode_layer_name(pb_ostream_t *stream, const pb_field_t *field, void *const *arg) {
+    const uint8_t layer_idx = *(uint8_t *)*arg;
+
+    const char *name = zmk_keymap_layer_name(layer_idx);
+
+    if (!name) {
+        return true;
+    }
+
+    if (!pb_encode_tag_for_field(stream, field)) {
+        return false;
+    }
+
+    return pb_encode_string(stream, name, strlen(name));
+}
+
+static bool encode_keymap_layers(pb_ostream_t *stream, const pb_field_t *field, void *const *arg) {
+    for (int l = 0; l < ZMK_KEYMAP_LAYERS_LEN; l++) {
+
+        if (!pb_encode_tag_for_field(stream, field)) {
+            LOG_DBG("Failed to encode tag");
+            return false;
+        }
+
+        zmk_keymap_Layer layer = zmk_keymap_Layer_init_zero;
+
+        layer.name.funcs.encode = encode_layer_name;
+        layer.name.arg = &l;
+
+        layer.bindings.funcs.encode = encode_layer_bindings;
+        layer.bindings.arg = &l;
+
+        if (!pb_encode_submessage(stream, &zmk_keymap_Layer_msg, &layer)) {
+            LOG_DBG("Failed to encode layer submessage");
+            return false;
+        }
+    }
+
+    return true;
+}
+
+zmk_Response get_keymap(const zmk_Request *req) {
+    zmk_keymap_Keymap resp = zmk_keymap_Keymap_init_zero;
+
+    resp.layers.funcs.encode = encode_keymap_layers;
+
+    return KEYMAP_RESPONSE(get_keymap, resp);
+}
+
+zmk_Response set_layer_binding(const zmk_Request *req) {
+    const zmk_keymap_SetLayerBindingRequest *set_req =
+        &req->subsystem.keymap.request_type.set_layer_binding;
+
+    zmk_behavior_local_id_t bid = set_req->binding.behavior_id;
+
+    const char *behavior_name = zmk_behavior_find_behavior_name_from_local_id(bid);
+
+    if (!behavior_name) {
+        return KEYMAP_RESPONSE(set_layer_binding,
+                               zmk_keymap_SetLayerBindingResponse_INVALID_BEHAVIOR);
+    }
+
+    struct zmk_behavior_binding binding = (struct zmk_behavior_binding){
+        .behavior_dev = behavior_name,
+        .param1 = set_req->binding.param1,
+        .param2 = set_req->binding.param2,
+    };
+
+    int ret = zmk_behavior_validate_binding(&binding);
+    if (ret < 0) {
+        return KEYMAP_RESPONSE(set_layer_binding,
+                               zmk_keymap_SetLayerBindingResponse_INVALID_PARAMETERS);
+    }
+
+    ret = zmk_keymap_set_layer_binding_at_idx(set_req->layer, set_req->key_position, binding);
+
+    if (ret < 0) {
+        LOG_DBG("Setting the binding failed with %d", ret);
+        switch (ret) {
+        case -EINVAL:
+            return KEYMAP_RESPONSE(set_layer_binding,
+                                   zmk_keymap_SetLayerBindingResponse_INVALID_LOCATION);
+        default:
+            return ZMK_RPC_SIMPLE_ERR(GENERIC);
+        }
+    }
+
+    return KEYMAP_RESPONSE(set_layer_binding, zmk_keymap_SetLayerBindingResponse_SUCCESS);
+}
+
+zmk_Response save_changes(const zmk_Request *req) {
+    int ret = zmk_keymap_save_changes();
+    if (ret < 0) {
+        return ZMK_RPC_SIMPLE_ERR(GENERIC);
+    }
+
+    return KEYMAP_RESPONSE(save_changes, true);
+}
+
+zmk_Response discard_changes(const zmk_Request *req) {
+    int ret = zmk_keymap_discard_changes();
+    if (ret < 0) {
+        return ZMK_RPC_SIMPLE_ERR(GENERIC);
+    }
+
+    return KEYMAP_RESPONSE(discard_changes, true);
+}
+
+ZMK_RPC_SUBSYSTEM_HANDLER(keymap, get_keymap, true);
+ZMK_RPC_SUBSYSTEM_HANDLER(keymap, set_layer_binding, true);
+ZMK_RPC_SUBSYSTEM_HANDLER(keymap, save_changes, true);
+ZMK_RPC_SUBSYSTEM_HANDLER(keymap, discard_changes, true);
+
+static int event_mapper(const zmk_event_t *eh, zmk_Notification *n) { return 0; }
+
+ZMK_RPC_EVENT_MAPPER(keymap, event_mapper);