lkml.org 
[lkml]   [2018]   [Dec]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH 1/2] drm/fb-helper: Bring back workaround for bugs of SDL 1.2
From
Date
On Thu, 2018-12-27 at 13:00 +0100, Daniel Vetter wrote: 
> > + /*
> > + * Workaround for SDL 1.2, which is known to be setting all pixel format
> > + * fields values to zero in some cases. We treat this situation as a
> > + * kind of "use some reasonable autodetected values".
> > + */
> > + if (!var->red.offset && !var->green.offset &&
> > + !var->blue.offset && !var->transp.offset &&
> > + !var->red.length && !var->green.length &&
> > + !var->blue.length && !var->transp.length &&
> > + !var->red.msb_right && !var->green.msb_right &&
> > + !var->blue.msb_right && !var->transp.msb_right) {
> > + u8 depth;
> > +
> > + /*
> > + * There is no way to guess the right value for depth when
> > + * bpp is 16 or 32. So we just restore the behaviour previously
> > + * introduced here by commit 785b93ef8c309. In fact, this was
> > + * implemented even earlier in various device drivers.
> > + */
> > + switch (var->bits_per_pixel) {
> > + case 16:
> > + depth = 15;
> > + break;
> > + case 32:
> > + depth = 24;
> > + break;
> > + default:
> > + depth = var->bits_per_pixel;
> > + break;
> > + }
>
> The guesswork here looks fishy. We should still have the drm-side format,
> and should use that.

This existed for a very long time until problematic commit was applied.
And there is a clear evidence that it was actually used by
applications.

> Otherwise the patches look good I think, but they
> need a Fixes: tag and cc: stable so backporters know what to do with
> these.
>

I added "cc: stable" into the regression fix. Also added more info into
the commit messages. See the PATCH v1 in the mailing list.

Thanks.



\
 
 \ /
  Last update: 2018-12-28 00:27    [W:0.099 / U:5.184 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site