Hi Geert. > > > > > > Yeah I don't think we should describe these with bpp or cpp or anything > > > like that. bpp < 8 makes sense since that's how this has been done since > > > decades, but trying to extend these to funny new formats is a bad idea. > > > This is also why cpp and depth refuse to compute these (or at least > > > should). > > > > Daniel and I discussed this on irc. Let me try to recap here. > > Using the bits per pixel info from drm_format_info is something we shall > > try to avoid as this is often a sign of the wrong abstraction/design (my > > words based on the irc talk). > > So we shall limit the use of drm_format_info_bpp() to what we need now, > > thus blocky formats should not be supported - to try to avoid seeing > > this used more than necessary. > > > > Daniel suggested a rename to drm_format_info_legacy_bpp() to make it > > obvious that this is often/always the wrong solution. I did not jump on > > doing the rename as I do not know stuff good enough to tell people what > > to use when this is not the right solution. The rename is simple, it is > > the follow-up that keep me away. > > > > On top of this there is a few formats in drm_drourcc that has a depth > > field set which should be dropped. .depth is only for the few legacy > > formats where it is used today. > > > > We would also like to convert the fbdev helpers to drm_format_info, > > and doing so will likely teach us a bit more what we need and what we > > can drop. > > > > Geert - can you give drm_format_info_bpp() a spin so it is limited to > > the formats used now (not the blocky ones). > > You mean return 0 if char_per_block[] > 1? if char_per_block[] > 1 AND block_w[] > 0 AND block_h[] > 0 should be enough. > I'm not sure it's actually safe to do so (and make this change this late > in the development cycle), as this is used in drm_client_buffer_create(), > drm_client_buffer_addfb(), and drm_mode_getfb(). drm_client_buffer_create() and drm_client_buffer_addfb() both get their format from drm_mode_legacy_fb_format() which do not produce any blocky formats - so they are good. drm_mode_getfb() looks up a framebuffer originally created using one of the above (I think), so here it should also be fine. I do not see the need to push this to fixes, so it has a full cycle to mature if it causes issues. Sam
