Hi, On Wed, May 11, 2022 at 12:14 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > > Hi > > Am 10.05.22 um 22:51 schrieb Douglas Anderson: > > If we're unable to read the EDID for a display because it's corrupt / > > bogus / invalid then we'll add a set of standard modes for the > > display. When userspace looks at these modes it doesn't really have a > > good concept for which mode to pick and it'll likely pick the highest > > resolution one by default. That's probably not ideal because the modes > > were purely guesses on the part of the Linux kernel. > > I'm skeptical. Why does the kernel do a better job than userspace here? > Only the graphics driver could possibly make such a decision. > > Not setting any preferred mode at least gives a clear message to userspace. OK, that's a fair point. So I tried to find out what our userspace is doing. I believe it's: https://source.chromium.org/chromium/chromium/src/+/main:ui/ozone/platform/drm/common/drm_util.cc;l=529 Specifically this bit of code: // If we still have no preferred mode, then use the first one since it should // be the best mode. if (!*out_native_mode && !modes.empty()) *out_native_mode = modes.front().get(); Do you agree with what our userspace is doing here, or is it wrong? If our userspace is doing the right thing, then I guess the problem is the call to "drm_mode_sort(&connector->modes);" at the end of drm_helper_probe_single_connector_modes(). Would you be OK with me _not_ sorting the modes in the "bad EDID" case? That also seems to fix my problem... -Doug
