[Spice-devel] [drm/qxl v2 7/7] qxl: Allow resolution which are not multiple of 8

[Christophe Fergeau]

On Thu, Nov 03, 2016 at 09:53:48AM +0100, Gerd Hoffmann wrote:
> On Mi, 2016-11-02 at 18:00 +0100, Christophe Fergeau wrote:
> > The use of drm_cvt_mode() in qxl_add_monitors_config_modes() means that
> > the resolutions we are going to present to user-space are going to be
> > rounded down to a multiple of 8. In the QXL arbitrary resolution case,
> > this is not useful.
> > This commit forces the actual width/height that was requested by the
> > client in the drm_display_mode structure rather than keeping the
> > rounded version.
> 
> Hmm, not sure this is a good idea.  There are probably reasons why
> drm_cvt_mode is rounding down ...

Yeah, I'm sure there are reasons, but I don't know what they are.
drm_cvt_mode seems to be calculating various frequencies and timings
related to refreshing real world monitors, and this seems to be defined
by some VESA standard. Maybe the rounding down is because the real-world
monitors or VESA require it. Or maybe other parts of the
kernel/userspace rely on this rounding down. I unfortunately don't know
:( Any guidance there whether that's ok, or whether I should approach
this differently would be very useful.

Christophe
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 801 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/spice-devel/attachments/20161103/013280ea/attachment.sig>