Re: [Linux-fbdev-users] matroxfb: supports gamma on primary VGA out?

[Petr V. <van...@vc...>]

Stephen Kell wrote:
> I'm trying to set gamma correction on the primary VGA output of my
> Matrox G400 dual-head, using matroxfb with kernel 2.6.24. 
> 
> Using matroxset, the ioctl completes successfully, but there is no
> effect.
> 
> stephen@alonzo:~$ strace matroxset -f /dev/fb0 -o 0 -c 0x980910 18 2>&1 | grep ioctl 
> ioctl(3, MATROXFB_G_TVOCTRL or VIDIOC_G_CTRL, 0xbfaec7d4) = 0
> ioctl(3, MATROXFB_S_TVOCTRL or VIDIOC_S_CTRL, 0xbfaec7d4) = 0
> 
> I've tried other controls (contrast, brightness etc.), with a range of
> arguments, and none has any visible effect.
> 
> Looking in matroxfb_base.c, it looks like the implementation of
> VIDIOC_S_CTRL is hardwired to use output 1. However, if I try with
> CRTC1 duplicated to output 1 (using matroxset -f /dev/fb0 -o 1 128), it
> still shows no effect. 
> 
> Is this a bug, or am I missing something? Thanks for any help.

These ioctls control only TV output - MATROXFB_S_*TVO*CTRL.  If you want 
VGA gamma correction, do it in software - Matrox G400/450/550 is 8bit 
only, so it is not very interesting to push this task to hardware if you 
are using 24/32bpp mode.
								Petr