[Intel-gfx] [PATCH 1/3] drm/i915: Don't set mode_config's cursor size

[Chris Wilson]

On Tue, Mar 25, 2014 at 04:05:29PM +0000, Damien Lespiau wrote:
> On Tue, Mar 25, 2014 at 03:09:16PM +0000, Chris Wilson wrote:
> > On Tue, Mar 25, 2014 at 02:59:18PM +0000, Damien Lespiau wrote:
> > > On Tue, Mar 25, 2014 at 02:54:56PM +0000, Chris Wilson wrote:
> > > > On Tue, Mar 25, 2014 at 02:49:30PM +0000, Damien Lespiau wrote:
> > > > > Those fields are supposed to be a good default value for the cursor
> > > > > size, intended for the case where the hardware doesn't support 64x64
> > > > > cursors, for use with a hw agnostic DDX driver for instance.
> > > > > 
> > > > > We're fine with 64x64 cursors though and don't need to set those fields
> > > > > (DRM core will return 64 is we don't). If we declare 256x256, that
> > > > > generic driver will use a big buffer for the cursor, without any good
> > > > > reason.
> > > > 
> > > > How does userspace now know that 256x256 cursors are support for HiDPI?
> > > 
> > > It doesn't currently? a property on the cursor plane with the list of
> > > supported formats in the brave new full drm_plane world seems like a
> > > good option to me.
> > 
> > Userspace currently uses this method to determine the largest cursor
> > supported by the driver. That userspace is inept at resize the cursor bo
> > as required is a probably that won't be solved by simply exposing it
> > later.
> 
> That doesn't seem to be the intention of the original patch?
> 
> http://lists.freedesktop.org/archives/dri-devel/2014-February/053770.html

For the record,

16:30 < agd5f> ickle, our GPUs don't have selectable cursor sizes
16:31 < agd5f> so on the newer ones, xf86-video-modesetting, etc. would
allocate a 64x64 cursor and it would look squashed and funky since the
hw expects 128x128

Which means I was confused when I thought part of the reasoning was
indeed HiDPI support. (I'm still seem to remember that was part of the
argument for large cursors anyway.)

> Are you saying the Intel DDX currently derives a different meaning to
> the intented behaviour? in which case it can still be changed to not do
> that?

I still disagree though. This provides all the information I need to
support variable sized cursors and we can use large cursors today.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre