Import of the watch repository from Pebble

src/fw/drivers/backlight.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+typedef enum {
+  LEDEnablerNone = (1 << 0),
+  LEDEnablerBacklight = (1 << 1),
+  LEDEnablerHRM = (1 << 2),
+} LEDEnabler;
+
+// The light brightness can vary between LIGHT_BRIGHTNESS_OFF and LIGHT_BRIGHTNESS_ON
+#define BACKLIGHT_BRIGHTNESS_OFF  0x0000
+#define BACKLIGHT_BRIGHTNESS_MAX  0x4000
+
+void backlight_init(void);
+
+//! @param brightness a number between BACKLIGHT_BRIGHTNESS_OFF and BACKLIGHT_BRIGHTNESS_ON
+void backlight_set_brightness(uint16_t brightness);
+
+//! On some boards, the LED enable gpio is actually a toggle for 4.5v.
+//! Other portions of the system may require this to be enabled in order to function.
+//! Keep track of who is using the LED enable so that way we don't turn it off on them.
+//! Those components which may need to toggle LED Enable are listed in \ref LEDEnabler.
+void led_enable(LEDEnabler enabler);
+
+void led_disable(LEDEnabler enabler);