Adding rotation to xf86-video-omapfb

[Maarten Maathuis]

On Fri, Dec 28, 2012 at 2:08 AM, Maarten Maathuis <madman2003 at gmail.com> wrote:
> On Thu, Dec 27, 2012 at 8:48 PM, Denis 'GNUtoo' Carikli
> <GNUtoo at no-log.org> wrote:
>> Hi,
>>
>> I've been trying to add rotation to the out of tree
>> xf86-video-omapfb(I'm aware of xf86-video-omap but I've an omap3, and
>> beside, it requires a staging kernel driver).
>>
>> So far I got rotation working(xrandr -o 1 works).
>>
>> But when I want to rotate back (xrandr -o 0) Xorg checks if the
>> requested X resolution is smaller or equals to the masimum allowed
>> Xresolution and it fails...
>>
>> The thing is that I've been using a hack to make it work:
>> instead of keeping the same resolution and just making rotate the
>> display content, I've changed the resolution too.
>>
>> My device is the GTA04 and it has a 480x640 display, so when rotating a
>> new mode is created(640x480):
>> root at om-gta04:~# xrandr -q
>> Screen 0: minimum 8 x 8, current 640 x 480, maximum 480 x 640
>> LCD connected 640x480+0+0 left (normal left inverted right x axis y
>> axis) 0mm x 0mm
>>    640x480        66.8 +
>>   480x640 (0x41)   22.2MHz
>>         h: width   480 start  504 end  512 total  520 skew    0 clock
>> 42.6KHz
>>         v: height  640 start  644 end  646 total  648           clock
>> 65.7Hz
>>
>> This shouldn't happen and instead I should use the normal approach,
>> which is not to change the resolution...
>>
>> But that fails too: My display is in portrait mode, and so when
>> rotating the image changes to 640x480, from the point 0.0 and isn't
>> rotated, which result in the image going over the physical screen
>> dimentions...
>>
>> The code I've been developing is here:
>> https://gitorious.org/gnutoo-s-programs-for-shr/xf86-video-omapfb/commit/834a2b938cbff98e6f69ff66789cf422e3e2d483
>>
>> I'd like to make the "correct way" work and rotate, but I've no idea of
>> how...
>>
>> Denis.
>> _______________________________________________
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>
> As far as i remember you typically allocate a shadow (there are some
> driver hooks for that, check existing drivers like intel, radeon or
> nouveau). This will become the new scanout buffer and this has the
> rotated dimensions. The original rendering will still be done to the
> "normal" framebuffer. Composite with rotation in combination with
> damage (a system used in X to track what areas have been rendered to
> i.e. damaged) is used to keep the shadow up to date.
>
> You should probably implement the shadow hooks that are present in the
> crtc structure. You should make sure this shadow allocation gets used
> as the framebuffer. And you should check if your composite
> implementation supports rotation, if not it may be necessary to expand
> it with support for any scaling/rotation matrix or else add a special
> case for 90 degree rotation if your hardware supports that.
>
> --
> Far away from the primal instinct, the song seems to fade away, the
> river get wider between your thoughts and the things we do and say.

I forgot to mention that decision/logic for the shadow allocation is
done inside the xserver, so it's not a choice you have.

-- 
Far away from the primal instinct, the song seems to fade away, the
river get wider between your thoughts and the things we do and say.