linux-kernel - Re: KMS + fb + FBIOPUT

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Date:	Wed, 29 Apr 2009 17:27:11 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Peter Hanzel <hanzelpeter@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-fbdev-devel@...ts.sourceforge.net
Subject: Re: KMS + fb + FBIOPUT_VSCREENINFO

On Tue, Apr 28, 2009 at 6:32 PM, Peter Hanzel <hanzelpeter@...il.com> wrote:
> Hello.
>
> I have tried DRM with intel KMS and it is workiing. I am using only
> framebuffer console.
> Fbcon initializes 1280x800 mode and it works like a charm.
>
> But when I try to call FBIOPUT_VSCREENINFO on /dev/fb0, it always returns
> EINVAL,
> I have checked drivers/gpu/drm/i915/intel_fb.c
> and found that
>
> intelfb_check_var        returns -EINVAL     if (var->pixclock == -1 ||
> !var->pixclock)
> intelfb_set_par             returns -EINVAL    if (var->pixclock != -1) {
> DRM_ERROR("PIXEL CLCOK SET\n");  return
>
> So the FBIOPUT_VSCREENINFO always fails.
>
> So is the change of resolution not supported through FBIOPUT_VSCREENINFO
> call?
>

The problem we've had is defining proper semantics for what happens in
multi-output systems when
 you call this ioctl. Which crtc/output should it set the mode on?
what happens if the mode isn't valid on all
connected monitors etc.

It should be quite trivial to hook up in fact I already did it once before.

I think we probably need some sysfs or fb ioctl to configure which
crtc/output combos will get controlled
by an fbset.

kms also has an option to run with one fb per crtc, which could also
be checked out. I'm not sure how much further we got with it.

Dave.

> Thanks.
>
>
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