fix(studio): Allow setting UART RPC thread priority (#3290)

To ensure we can tune things when other threads may have priority,
preventing UART processing in time for the studio UI requirements,
adjust our default UART thread priority, and allow overriding as needed.

.github/workflows/ble-test.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
       - name: Find test directories
         id: test-dirs
         run: |
@@ -38,7 +38,7 @@ jobs:
       image: docker.io/zmkfirmware/zmk-build-arm:4.1
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
       - name: Cache west modules
         uses: actions/cache@v4
         env:

.github/workflows/build-user-config.yml

@@ -33,7 +33,7 @@ jobs:
       has_valid_build_matrix: ${{ steps.fetch.outputs.has_valid_build_matrix }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
 
       - name: Fetch Build Matrix
         id: fetch
@@ -67,7 +67,7 @@ jobs:
           curl -fsSL https://deb.nodesource.com/setup_22.x | bash && apt install -y nodejs
 
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
 
       - name: Create build directory
         run: |

.github/workflows/build.yml

@@ -30,7 +30,7 @@ jobs:
         include: ${{ fromJSON(needs.compile-matrix.outputs.include-list) }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
         with:
           persist-credentials: false
       - name: Cache west modules
@@ -187,7 +187,7 @@ jobs:
       core-include: ${{ steps.core-list.outputs.result }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
         with:
           persist-credentials: false
       - name: Use Node.js
@@ -218,7 +218,7 @@ jobs:
       boards-include: ${{ steps.boards-list.outputs.result }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
       - name: Use Node.js
         uses: actions/setup-node@v4
         with:
@@ -346,7 +346,7 @@ jobs:
       organized-metadata: ${{ steps.organize-metadata.outputs.result }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
         with:
           persist-credentials: false
       - name: Use Node.js
@@ -428,7 +428,7 @@ jobs:
       core-changes: ${{ steps.core-changes.outputs.result }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
         with:
           persist-credentials: false
       - uses: tj-actions/changed-files@9200e69727eb73eb060652b19946b8a2fdfb654b # pin to v45.0.8 due to https://github.com/tj-actions/changed-files/issues/2463 https://www.stepsecurity.io/blog/harden-runner-detection-tj-actions-changed-files-action-is-compromised

.github/workflows/doc-checks.yml

@@ -14,7 +14,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v5
       - uses: bahmutov/npm-install@v1
         with:
           working-directory: docs
@@ -24,7 +24,7 @@ jobs:
   typecheck:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v5
       - uses: bahmutov/npm-install@v1
         with:
           working-directory: docs

.github/workflows/hardware-metadata-validation.yml

@@ -20,7 +20,7 @@ jobs:
     container:
       image: docker.io/zmkfirmware/zmk-dev-arm:4.1
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v5
       - name: Install dependencies
         run: pip install --break-system-packages -r app/scripts/requirements.txt
       - name: West init

.github/workflows/pre-commit.yml

@@ -8,7 +8,7 @@ jobs:
   pre-commit:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v5
       - uses: actions/setup-python@v5
         with:
           python-version: 3.x

.github/workflows/release-please.yml

@@ -35,7 +35,7 @@ jobs:
       ZMK_RELEASE_PLEASE_TOKEN: ${{ secrets.ZMK_RELEASE_PLEASE_TOKEN }}
       VERSION: v${{ needs.handle-commit.outputs.major }}.${{ needs.handle-commit.outputs.minor }}
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v5
 
       - name: Create major.minor branch
         if: ${{ needs.handle-commit.outputs.patch == '0' }}

.github/workflows/test.yml

@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
       - name: Find test directories
         id: test-dirs
         run: |
@@ -40,7 +40,7 @@ jobs:
       image: docker.io/zmkfirmware/zmk-build-arm:4.1
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v5
       - name: Cache west modules
         uses: actions/cache@v4
         env:

app/src/studio/Kconfig

@@ -59,11 +59,20 @@ config ZMK_STUDIO_TRANSPORT_UART
     select RING_BUFFER
     default y if $(dt_chosen_enabled,$(DT_CHOSEN_ZMK_STUDIO_RPC_UART))
 
+if ZMK_STUDIO_TRANSPORT_UART
+
 config ZMK_STUDIO_TRANSPORT_UART_RX_STACK_SIZE
     int "RX Stack Size"
     depends on !UART_INTERRUPT_DRIVEN
     default 512
 
+config ZMK_STUDIO_TRANSPORT_UART_RX_PRIORITY
+    int "RX Thread Priority"
+    depends on !UART_INTERRUPT_DRIVEN
+    default 9
+
+endif
+
 config ZMK_STUDIO_TRANSPORT_BLE
     bool "BLE (GATT)"
     select RING_BUFFER
@@ -71,9 +80,12 @@ config ZMK_STUDIO_TRANSPORT_BLE
     depends on ZMK_BLE
     default y
 
+
 config BT_CONN_TX_MAX
     default 64 if ZMK_STUDIO_TRANSPORT_BLE
 
+if ZMK_STUDIO_TRANSPORT_BLE
+
 config ZMK_STUDIO_TRANSPORT_BLE_PREF_LATENCY
     int "BLE Transport preferred latency"
     default 10
@@ -81,6 +93,8 @@ config ZMK_STUDIO_TRANSPORT_BLE_PREF_LATENCY
       When the studio UI is connected, a lower latency can be requested in order
       to make the interactions between keyboard and studio faster.
 
+endif
+
 endmenu
 
 config ZMK_STUDIO_RPC_THREAD_STACK_SIZE

app/src/studio/uart_rpc_transport.c

@@ -65,7 +65,7 @@ static void uart_rx_main(void) {
 }
 
 K_THREAD_DEFINE(uart_transport_read_thread, CONFIG_ZMK_STUDIO_TRANSPORT_UART_RX_STACK_SIZE,
-                uart_rx_main, NULL, NULL, NULL, K_LOWEST_APPLICATION_THREAD_PRIO, 0, 0);
+                uart_rx_main, NULL, NULL, NULL, CONFIG_ZMK_STUDIO_TRANSPORT_UART_RX_PRIORITY, 0, 0);
 
 #endif