On Thu, Nov 03, 2016 at 06:08:39PM +0100, Gerd Hoffmann wrote: > > Or maybe other parts of the > > kernel/userspace rely on this rounding down. > > This is where I suspect we could run in trouble. Odd resolutions simply > don't happen on physical hardware, all usual resolutions are a multiple > of 8, most of them are even a multiple of 16. > > Various image/video formats use 16x16 blocks. > The qemu vnc server operates on 16x16 blocks too (and we had bugs in the > past with odd resolutions). > > Also scanlines and cachelines align nicely if you don't use odd > resolutions. > > > I unfortunately don't know > > :( > > I don't have definitive answers too, just a gut feeling that this might > cause trouble. I think this might be fine actually, there is already one such resolution in the kernel, which is 1366x768 (1366 is only a multiple of 2). There is already a bit of a hack to handle it anyway, see fixup_mode_1366x768() in drm_edid.c. > > Maybe we should add a module option for this? So there is an easy > (as-in: doesn't require a kernel rebuild) way out in case it causes > trouble in certain setups? This seems a bit overkill to me, but I can look into it if needed. Christophe
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