blob: b854253e8e5b06d7c50ca4e03b700c5103969fb7 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
|
@page page_device_graphic_backlight Backlight devices
# Backlight subsystem
Header: `components/drivers/include/drivers/backlight.h`. Core: **`components/drivers/graphic/backlight/backlight.c`**. PWM and GPIO backends: **`backlight-pwm.c`**, **`backlight-gpio.c`**.
Graphic stack overview: @ref page_device_graphic_dm.
## `struct rt_backlight_device`
Extends **`rt_device`**. Properties include **`max_brightness`**, **`brightness`**, power state. Drivers implement brightness through ops registered with the core.
### Core device behavior (`backlight.c`)
| Op | Behavior |
| --- | --- |
| `read` | ASCII decimal of current brightness |
| `write` | Parse integer string, clamp to **`max_brightness`**, call **`rt_backlight_set_brightness`** |
**`RT_DM_IDA_INIT(GRAPHIC_BACKLIGHT)`** assigns stable DM names on register.
## PWM backlight (`pwm-backlight`)
**Compatible**: typically **`pwm-backlight`** (see driver OFW table in source).
| DT / property | Role |
| --- | --- |
| `pwms` | PWM channel for dimming |
| `brightness-levels` | Optional non-linear LUT |
| `default-brightness-level` | Boot brightness index |
| `enable-gpios` | Panel enable pin |
| `power-supply` | Optional **`rt_regulator`** before PWM |
Probe enables regulator (if any), maps brightness levels, registers **`rt_backlight_device`**.
## GPIO backlight (`gpio-backlight`)
Simple on/off or few-level backlight using a GPIO line (see `backlight-gpio.c` OFW ids).
## Driver / BSP quick notes
| Topic | Guidance |
| --- | --- |
| Enable order | Regulator → enable GPIO → PWM duty |
| Thermal | High brightness may interact with @ref page_device_thermal policies |
| Userspace | Writing `"128\n"` to device node sets brightness (see core `write`) |
## See also
- @ref page_device_graphic_dm
- @ref page_device_regulator
- `components/drivers/graphic/backlight/backlight.c`
- `components/drivers/graphic/backlight/backlight-pwm.c`
|
