drm framebuffer/scanout buffer transform

[Michel Dänzer]

On Mon, 2012-05-14 at 12:56 -0600, Dan Walkes wrote: 
> 
> I’m working on a project to implement a color transformation of all
> pixels in the framebuffer.

That sounds like the per CRTC colour lookup table might fit the bill.
Grep for crtc_lut in drivers/gpu/drm/drm_crtc.c.


> I’ve found drm_mode_dirtyfb_ioctl is one ioctl which seems to be
> invoked whenever the display changes (as I move the mouse across the
> screen, start applications, etc) however I don’t see this method when
> I attempt to play a video with mplayer.  Based on my research I had
> expected video to use overlay buffers, however I also don’t see calls
> to overlay ioctls like vmw_overlay_ioctl, vmw_stream_*_ioctl.

These ioctls are only used by the vmwgfx drivers, which only support the
virtual GPU available in VMware hypervisors.


> I see references to the scanout buffer in drm_irq and intel_display
> within drm source, as well as in the documentation at
> http://www.kernel.org/doc/htmldocs/drm/ch02s05.html but I’m having a
> hard time figuring out where the scanout buffer actually *is*.  If I
> could understand the relationship between the framebuffer and scanout
> buffer better I could probably use this to figure out where I’d need
> to add my transform.

They're generally one and the same thing.


-- 
Earthling Michel Dänzer           |                   http://www.amd.com
Libre software enthusiast         |          Debian, X and DRI developer