Re: [linux-sunxi] Error -17 after inserting backlight module

[Jari Helaakoski]

2013/2/1 Manoj Gudi <manoj....@gmail.com>

I am a novice developer who is trying to control backlight-brightness on a A13 based tablet device running ubuntu 12.10 from sdcard.

None of user space methods of controlling brightness like modifying brightness in /sys/class/ or xbacklight -set, work (in fact ls /sys/class/backlight returns none)

Hi,

Backlight logic is integrated to disp module.

https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.0/drivers/video/sunxi/disp/disp_lcd.c#L1913

To control it you need to implement binding to sysfs. (And probably separate whole logic from disp to backlight module)

-Jari

[Manoj Gudi]

Jari Helaakoski wrote:
> 2013/2/1 Manoj Gudi <manoj....@gmail.com>
>
> > I am a novice developer who is trying to control backlight-brightness on a
> > A13 based tablet device running ubuntu 12.10 from sdcard.
> >

> > None of user space methods of controlling brightness like *modifying
> > brightness in /sys/class/* or *xbacklight -set, *work (in fact *ls
> > /sys/class/backlight* returns none)

> >
> Hi,
>
> Backlight logic is integrated to disp module.
> https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.0/drivers/video/sunxi/disp/disp_lcd.c#L1913
>

Agreed, I tried with inserting disp module after lcd, still it didn't
work.

> To control it you need to implement binding to sysfs. (And probably
> separate whole logic from disp to backlight module)
>

can you please elaborate on this?

> -Jari

thanks,
manojg

[Jari Helaakoski]

2013/2/1 Manoj Gudi <manoj....@gmail.com>

You need to implement functions to control brightness and then register them for backlight module 

Ie. https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.0/drivers/video/backlight/s6e63m0.c#L772

-Jari

[Manoj Gudi]

got it, thanks