Re: [PATCH] drm/vkms: Use alpha value to blend values.

[Sidong Yang]

On Mon, Sep 02, 2019 at 03:28:58PM +0300, Ville Syrjälä wrote:
> On Sat, Aug 31, 2019 at 06:25:46PM +0100, Sidong Yang wrote:
> > Use alpha value to blend source value and destination value Instead of
> > just overwrite with source value.
> > 
> > Signed-off-by: Sidong Yang <realwakka@xxxxxxxxx>
> > ---
> >  drivers/gpu/drm/vkms/vkms_composer.c | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> > index d5585695c64d..b776185e5cb5 100644
> > --- a/drivers/gpu/drm/vkms/vkms_composer.c
> > +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> > @@ -75,6 +75,9 @@ static void blend(void *vaddr_dst, void *vaddr_src,
> >  	int y_limit = y_src + h_dst;
> >  	int x_limit = x_src + w_dst;
> >  
> > +	u8 *src, *dst;
> > +	u32 alpha, inv_alpha;
> 
> These could all live in a tighter scope.

Hi, Ville.

Thank you for reviewing my patch.
I think that's good idea and I'll do that in next version.
I found some patch in mailing list that is similar with this patch.
So should I drop this patch and find other thing?

Sidong.

> 
> Apart from that lgtm
> Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> 
> > +
> >  	for (i = y_src, i_dst = y_dst; i < y_limit; ++i) {
> >  		for (j = x_src, j_dst = x_dst; j < x_limit; ++j) {
> >  			offset_dst = dest_composer->offset
> > @@ -84,8 +87,14 @@ static void blend(void *vaddr_dst, void *vaddr_src,
> >  				     + (i * src_composer->pitch)
> >  				     + (j * src_composer->cpp);
> >  
> > -			memcpy(vaddr_dst + offset_dst,
> > -			       vaddr_src + offset_src, sizeof(u32));
> > +			src = vaddr_src + offset_src;
> > +			dst = vaddr_dst + offset_dst;
> > +			alpha = src[3] + 1;
> > +			inv_alpha = 256 - src[3];
> > +			dst[0] = (alpha * src[0] + inv_alpha * dst[0]) >> 8;
> > +			dst[1] = (alpha * src[1] + inv_alpha * dst[1]) >> 8;
> > +			dst[2] = (alpha * src[2] + inv_alpha * dst[2]) >> 8;
> > +			dst[3] = 0xff;
> >  		}
> >  		i_dst++;
> >  	}
> > -- 
> > 2.20.1
> > 
> > _______________________________________________
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> 
> -- 
> Ville Syrjälä
> Intel