On Thu, Jul 11, 2019 at 10:28 AM Simon Ser <contact@xxxxxxxxxxx> wrote: > > On Thursday, July 11, 2019 11:21 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: > > > On Tue, Jun 25, 2019 at 10:38:31PM -0300, Rodrigo Siqueira wrote: > > > > > The compute_crc() function is responsible for calculating the > > > framebuffer CRC value; due to the XRGB format, this function has to > > > ignore the alpha channel during the CRC computation. Therefore, > > > compute_crc() set zero to the alpha channel directly in the input > > > framebuffer, which is not a problem since this function receives a copy > > > of the original buffer. However, if we want to use this function in a > > > context without a buffer copy, it will change the initial value. This > > > patch makes compute_crc() calculate the CRC value without modifying the > > > input framebuffer. > > > > Uh why? For writeback we're writing the output too, so we can write > > whatever we want to into the alpha channel. For writeback we should never > > accept a pixel format where alpha actually matters, that doesn't make > > sense. You can't see through a real screen either, they are all opaque :-) > > I'm not sure about that. See e.g. > https://en.wikipedia.org/wiki/See-through_display They have variable opaqueness, independent of the color value? > Many drivers already accept FBs with alpha channels for the primary > plane. > https://drmdb.emersion.fr/formats?plane=1 If you have a background color (we assume it to be black) that makes sense. Still doesn't mean we render transparent output, we don't. > Just making sure we aren't painting ourselves into a corner. :P You can add ARGB to your writeback format support list, there is no corner here at all to get into (at least in the abstract sense). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
