display black: how to change backlight/pcf50633-bl/actual_brightness ?

[François TOURDE]

Le 14141ième jour après Epoch,
Harald Koenig écrivait:

> Hi,
>
> sometimes my FR just stays "black" while the Xglamo is still responsive.
> "actual_brightness" is zero, but it's not writable, so I can't change it
> from the shell:
>
> root at om-gta02:~# head  /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/*brightness
> ==> /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/actual_brightness <==
> 0
>
> ==> /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/brightness <==
> 63
>
> ==> /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/max_brightness <==
> 63
>
> root at om-gta02:~# ls -l /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/*brightness
> -r--r--r--    1 root     root            0 Sep 19 15:04 /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/actual_brightness
> -rw-r--r--    1 root     root            0 Sep 19 15:05 /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/brightness
> -r--r--r--    1 root     root         4096 Sep 19 15:04
> /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/max_brightness

Probably because *_brightness are read-only values, as unix perms
seems to indicate...

Try to write to:

/sys/class/backlight/pcf50633-bl/brightness 
or
/sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/brightness

Both are rw and works for me (tm).