On Fri, Sep 20, 2019 at 9:20 AM Maxime Ripard mripard@kernel.org wrote:
On Thu, Sep 19, 2019 at 08:53:10PM +0200, Jernej Škrabec wrote:
Dne sreda, 18. september 2019 ob 13:05:41 CEST je roman.stratiienko@globallogic.com napisal(a):
From: Roman Stratiienko roman.stratiienko@globallogic.com
According to Allwinner DE2.0 Specification REV 1.0, vi layer supports the following pixel formats: ABGR_8888, ARGB_8888, BGRA_8888, RGBA_8888
It's true that DE2 VI layers support those formats, but it wouldn't change anything because alpha blending is not supported by those planes. These formats were deliberately left out because their counterparts without alpha exist, for example ABGR8888 <-> XBGR8888. It would also confuse user, which would expect that alpha blending works if format with alpha channel is selected.
I'm not too familiar with the DE2 code, but why is alpha not working if the VI planes support formats with alpha?
Good question. It mentioned in the datasheet https://linux-sunxi.org/images/7/7b/Allwinner_DE2.0_Spec_V1.0.pdf on page 95: "All ui layers' alpha is useless" And my experiments proves it.
My assumption that vi uses post-processing that cuts out alpha values.
Thanks! Maxime