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: Graphics (DM).

<tt>struct rt_backlight_device</tt>

Extends **rt_device**. Properties include **max_brightness**, **brightness**, power state. Drivers implement brightness through ops registered with the core.

Core device behavior (<tt>backlight.c</tt>)

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 (<tt>pwm-backlight</tt>)

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 (<tt>gpio-backlight</tt>)

Simple on/off or few-level backlight using a GPIO line (see backlight-gpio.c OFW ids).

Driver / BSP quick notes