On Thu, Dec 04, 2014 at 08:27:41PM +0000, Adam Cheney wrote:
> Hi dri-devel,
>
> I have a question about validating the user specified rectangles in SetCrtc
> and SetPlane.
>
> To me this is required for src_ or crtc_ rectangles to be legal, true for
> both SetCrtc and SetPlane:
>
>
> 1) src_{x,y,w,h} fits entirely within the fb size
>
> 2) crtc_{x,y,w,h} fits entirely within the mode size
>
> There is some common code that enforces 1), but 2) appears to be up to
> individual drivers to enforce (if they choose to) as far as I can tell.
>
> If the crtc_ output rectangle extends outside of the connector's active mode,
> should DRM drivers perform the mode clipping themselves, or should this be
> considered an application bug and an error code returned?
>
> Is there any reason not to enforce 2) in the core DRM code, rather than in
> the individual drivers?
We clip the crtc_ coords rather than require that they fit inside the crtc.
It's a bug for the driver not to do that as far as I'm concerned.
Since we do have sub-pixel src coordinates we could have required the crtc_
coordinates to stay within the crtc limits without losing functionality, but
allowing them to extend outside made it easier to write test code, and gave
me a nice excuse to push the drm_rect stuff ;)
--
Ville Syrjälä
Intel OTC
