Default Figuring out the driver used for lcd-backlight

On my device vega a870k,

Code:
/sys/devices/platform/msm_fb.591873/leds/lcd-backlight/device
the lcd backlight control sysfs driver points to

Code:
 driver -> ../../../bus/platform/drivers/msm_fb
doesn't seem to be useful in figuring out what exactly is being used for the driver. Unlike the led controls which point to

Code:
../../devices/platform/msm_ssbi.0/pm8921-core/pm8xxx-led/
giving me hints that the driver should be something like pm8xxx


In the kernel source I see the following:

Code:
/arch/arm/configs/IM-A870K_defconfig
Code:
# CONFIG_FB_MSM_BACKLIGHT is not set
CONFIG_BACKLIGHT_LCD_SUPPORT=y
CONFIG_BACKLIGHT_CLASS_DEVICE=y
Code:
/driver/video/backlight/kconfig
there are tons of menu config items, such as

Code:
config BACKLIGHT_LP855X
	tristate "Backlight driver for TI LP855X"
	depends on BACKLIGHT_CLASS_DEVICE && I2C
	help
	  This supports TI LP8550, LP8551, LP8552, LP8553 and LP8556
	  backlight driver.
Now, I suppose the relevant building instruction should be contained in IM-A870K_defconfig. However, I find no references in building for any backlight driver.

What am I missing here? IM-A870K_defconfig attached.


I am looking at this because the backlight minimum level is way too bright. Haking system framework apk or using gravitybox to lower the minium brightness doesn't help - 20 seems to be the kernel limit in how low the brightness can go down. Values of 7-19 doesn't differ from 20, and values less than 7 turns off the backlight entirely. There is probably a constant minimum defined in the driver which is probably not exposed to sysfs control because there doesn't seem to have a register file for the minimum backlight current.


Thank you!


Edit: Several menu item in drivers/video/backlight/Kconfig has default value of y

Code:
config BACKLIGHT_GENERIC
	tristate "Generic (aka Sharp Corgi) Backlight Driver"
	default y
	help
	  Say y to enable the generic platform backlight driver previously
	  known as the Corgi backlight driver. If you have a Sharp Zaurus
	  SL-C7xx, SL-Cxx00 or SL-6000x say y.

config BACKLIGHT_LOCOMO
	tristate "Sharp LOCOMO LCD/Backlight Driver"
	depends on SHARP_LOCOMO
	default y
	help
	  If you have a Sharp Zaurus SL-5500 (Collie) or SL-5600 (Poodle) say y to
	  enable the LCD/backlight driver.

config BACKLIGHT_OMAP1
	tristate "OMAP1 PWL-based LCD Backlight"
	depends on ARCH_OMAP1
	default y
	help
	  This driver controls the LCD backlight level and power for
	  the PWL module of OMAP1 processors.  Say Y if your board
	  uses this hardware.

config BACKLIGHT_HP680
	tristate "HP Jornada 680 Backlight Driver"
	depends on SH_HP6XX
	default y
	help
	  If you have a HP Jornada 680, say y to enable the
	  backlight driver.

config BACKLIGHT_HP700
	tristate "HP Jornada 700 series Backlight Driver"
	depends on SA1100_JORNADA720_SSP && !PREEMPT
	default y
	help
	  If you have an HP Jornada 700 series,
	  say Y to include backlight control driver.

It looks like msm_fb.C and msm_fb_bl.C in drivers/video/msm/ gives the generic sysfs interface to control lcd backlight brightness, but I still am unable to figure out the actual driver for the backlight driver chip used.