On 09/17/2015 11:53 AM, Thomas Hellstrom wrote:
> On 09/17/2015 11:34 AM, Jose Fonseca wrote:
>> On 16/09/15 14:04, Thomas Hellstrom wrote:
>>> XA has been using L8_UNORM for a8 and yuv component surfaces.
>>> This commit instead makes XA prefer R8_UNORM since it's assumed to
>>> have a
>>> higher availability.
>>>
>>> Also neither of these formats are suitable as destination formats using
>>> destination alpha blending, so reject those operations.
>>>
>>> Signed-off-by: Thomas Hellstrom <thellst...@vmware.com>
>>> ---
>>> src/gallium/state_trackers/xa/xa_composite.c | 40
>>> ++++++++++------------------
>>> src/gallium/state_trackers/xa/xa_tracker.c | 28 +++++++++++++------
>>> 2 files changed, 34 insertions(+), 34 deletions(-)
>>>
>>> diff --git a/src/gallium/state_trackers/xa/xa_composite.c
>>> b/src/gallium/state_trackers/xa/xa_composite.c
>>> index 7cfd1e1..e81eeba 100644
>>> --- a/src/gallium/state_trackers/xa/xa_composite.c
>>> +++ b/src/gallium/state_trackers/xa/xa_composite.c
>>> @@ -78,26 +78,6 @@ static const struct xa_composite_blend xa_blends[]
>>> = {
>>> 0, 0, PIPE_BLENDFACTOR_ONE, PIPE_BLENDFACTOR_ONE},
>>> };
>>>
>>> -
>>> -/*
>>> - * The alpha value stored in a luminance texture is read by the
>>> - * hardware as color.
>>> - */
>>> -static unsigned
>>> -xa_convert_blend_for_luminance(unsigned factor)
>>> -{
>>> - switch(factor) {
>>> - case PIPE_BLENDFACTOR_DST_ALPHA:
>>> - return PIPE_BLENDFACTOR_DST_COLOR;
>>> - case PIPE_BLENDFACTOR_INV_DST_ALPHA:
>>> - return PIPE_BLENDFACTOR_INV_DST_COLOR;
>>> - default:
>>> - break;
>>> - }
>>> - return factor;
>>> -}
>>> -
>>> -
>>> static boolean
>>> blend_for_op(struct xa_composite_blend *blend,
>>> enum xa_composite_op op,
>>> @@ -131,10 +111,16 @@ blend_for_op(struct xa_composite_blend *blend,
>>> if (!dst_pic->srf)
>>> return supported;
>>>
>>> - if (dst_pic->srf->tex->format == PIPE_FORMAT_L8_UNORM) {
>>> - blend->rgb_src = xa_convert_blend_for_luminance(blend->rgb_src);
>>> - blend->rgb_dst = xa_convert_blend_for_luminance(blend->rgb_dst);
>>> - }
>>> + /*
>>> + * None of the hardware formats we might use for dst A8 are
>>> + * suitable for dst_alpha blending, since they present the
>>> + * alpha channel either in all color channels (L8_UNORM) or
>>> + * in the red channel only (R8_UNORM)
>>> + */
>>> + if ((dst_pic->srf->tex->format == PIPE_FORMAT_L8_UNORM ||
>>> + dst_pic->srf->tex->format == PIPE_FORMAT_R8_UNORM) &&
>>> + blend->alpha_dst)
>>> + return FALSE;
>> I'm not very familiar with this code, but wasn't
>> xa_convert_blend_for_luminance compensating for the A8 <-> L8
>> mismatch? It looks like it was doing the right thing. And
>> xa_convert_blend_for_luminance would work both for L8 and R8.
> In these operations since the destination format is A8, we're only
> interested in the resulting alpha channel. With
> PIPE_BLENDFACTOR_DST_ALPHA, we would use the destination alpha channel
> for blending, which would pick up 1 for L8 and R8 which is obviously
> wrong. Now the removed function instead set PIPE_BLENDFACTOR_DST_COLOR,
> which would, if I read the specs correctly blend component-wise and
> yield the correct results for the R, G and B channels if L8 is used. and
> for the R channel only if R8 is used. But a prerequisite here is that
> the destination logical format is A8 and the alpha channel is never
> correct AFAICT.
>
Hmm, or are you making the point that blending takes place when we've
already swizzled the alpha value to the red channel? Yes, then you're
obviously right, and I need to revert that "fix" ;).
/Thomas
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