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

[Michal Suchanek <hramrach@centrum.cz>]

On 3 March 2010 06:02, Dave Airlie <airlied@gmail.com> wrote:
> 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.
>

What about writing a drmfbset or something and have fbset call it when
it detects a drm framebuffer and warn that it does not support drm
framebuffers fully?

That way people using fbset still get something and people who want
exact control over the setup can use the new tool which uses whatever
KMS interface is available already.

Thanks

Michal

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