On Wed, 2010-11-03 at 08:57 +0100, ext Taneja, Archit wrote:
> Hi,
>
> linux-omap-ow...@vger.kernel.org wrote:
> > Alpha Support
> >
>
> [snip]
>
> >>
> >> +static void _dispc_set_pre_mult_alpha(enum omap_plane plane, bool
> >> +enable) {
> >> + if (!dss_has_feature(FEAT_PREMUL_ALPHA))
> >> + return;
> >> +
> >> + BUG_ON(!dss_has_feature(FEAT_GLOBAL_ALPHA_VID1) &&
> >> + plane == OMAP_DSS_VIDEO1);
> >
> > What is the rationale for having the function return, if
> > FEAT_PREMUL_ALPHA is not supported, but BUG if plane is video1 and
> > GLOBAL_ALPHA_VID1 is not supported?
>
> Premultiplied alpha is available on omap36xx and above, but on 36xx
> since global alpha itself isn't supported for video1 then writing to
> the pre multiplied alpha bit is incorrect.
>
> It could have been possible to make a new feature like FEAT_PRE_MULT_VID1
> but I think its redundant as FEAT_GLOBAL_ALPHA_VID1 is enough to determine
> if we should set the pre multiplied alpha bit for video1 plane or not.
I was referring to the first check using return, and the second using
BUG(). If nobody is supposed to call that function when
!dss_has_feature(FEAT_GLOBAL_ALPHA_VID1) && plane == OMAP_DSS_VIDEO1)
then why is it ok to call that function when
!dss_has_feature(FEAT_PREMUL_ALPHA)
Shouldn't they both be either returns or BUGs?
Tomi
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