Re: [Linux-fbdev-devel] drm_fb_helper: Impossible to change video mode

[Dave Airlie <airlied@gmail.com>]

On Mon, Mar 1, 2010 at 7:18 PM, Michal Suchanek <hramrach@centrum.cz> wrote:
> On 21 November 2009 05:27, Dave Airlie <airlied@gmail.com> wrote:
>
>> At the moment the problem with fbset is what to do with it in the
>> dual head case. Currently we create an fb console that is lowest
>> common size of the two heads and set native modes on both,
>
> Does that mean that fbset is supposed to work (set resolution) on drmfb?

No we've never hooked it up but it could be made work.

>
>>
>> Now if a user runs fbset, I'm not sure what the right answer is,
>> a) pick a head in advance via sysfs maybe and set it on that.
>> b) try and set the mode on both heads cloned (what to do if
>> there is no common mode is another issue).
>>
>
> I would say it's time to support multihead with fbset properly.
>
> That is people would need new fbset which sees both (all) heads, and
> fbset can then choose the head itself (and people can make it do
> something different when they don't like the default). It should also
> support setting up rotation on each head.
>
> For old fbset setting something visible is probably good enough.
>
> Schemes which would make a multihead setup look like a single screen
> get complicated quite easily. Perhaps an option to turn off some
> outputs so that the native resolution of one output is used (instead
> of clone) would work.
>

I've only really got two answer for this:

(a) hook up another /dev/dri/card_fb device and use the current KMS
ioctls to control the framebuffer, have the drm callback into fbdev/fbcon
to mention resizes etc. Or add one or two info gathering ioctls and
allow use of the /dev/dri/control device to control stuff.

(b) add a lot of ioctls to KMS fbdev device, which implement some sort
of sane multi-output settings.

Now the second sounds like a lot of work if not the correct solution,
you basically needs a way to pretty much expose what the KMS ioctls
expose on the fb device, and then upgrade fbset to make sense of it all.

Dave.

------------------------------------------------------------------------------
Download Intel&#174; Parallel Studio Eval
Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
See why Intel Parallel Studio got high marks during beta.
http://p.sf.net/sfu/intel-sw-dev
--