On Tue, Feb 1, 2022 at 9:34 AM Simon Ser <contact@xxxxxxxxxxx> wrote: > > On Tuesday, February 1st, 2022 at 09:26, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > > What's the story with the Rn formats? > > > > The comments say "n bpp Red", while this is a monochrome (even > > inverted) display? > > I don't think the color matters that much. "Red" was picked just because it was > an arbitrary color, to make the difference with e.g. C8. Or am I mistaken? The red comes from gl, where with shaders it really doesn't matter what meaning you attach to channels, but really just how many you have. So 2-channel formats are called RxGx, 3-channel RxGxBx, 4-channel RxGxBxAx and single-channel Rx. And we use drm_fourcc for interop in general, hence why these exist. We should probably make a comment that this really isn't a red channel when used for display it's a greyscale/intensity format. Aside from that documentation gap I think reusing Rx formats for greyscale/intensity for display makes perfect sense. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
