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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[7]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; URIBL_BLOCKED(0.00)[suse.com:url,suse.de:mid,imap1.dmz-prg2.suse.org:helo,emersion.fr:email]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:url,suse.de:mid] X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Am 04.05.26 um 12:30 schrieb Jani Nikula: > On Thu, 30 Apr 2026, Simon Ser wrote: >> The big one here is the "EDID" blob property exposed by KMS. We can't just put >> a DisplayID blob in there, that would break user-space. We'll need a new >> property. > I think the big question is what do we do with the EDID property when we > encounter a display with native DisplayID. > > The VESA E-DDC spec says the host should try DisplayID first, and not > read the EDID if a DisplayID is found. However, if we only update the > DisplayID property and not the EDID property, I think that'll be a > regression. Is there a technical problem/side effect/interference from reading both? > > So maybe we need to read both DisplayID and EDID, contrary to what the > E-DDC spec says. Obviously that means slower detection overall, for all > displays, old and new. Especially if there are errors reading DisplayID, > which you'd expect with old displays. IMHO we should 1) follow the spec and expose DisplayID first and EDID only if the former is not available, and 2) provide a kernel config option to provide both. People building kernel usually have control over user space as well. That option can be enabled by anyone with a legacy user space. This also puts some mild pressure on user space to implement DisplayID. > > There's an additional catch. The E-DDC spec says the capabilities in the > DisplayID don't need to be a strict superset of the capabilities in the > EDID. The idea is that the DisplayID is for new hosts, and the EDID is > for legacy and max interoperability. But if we read both and aim for no > regressions, we'll have to expose a union of the capabilities. > > Strict adherence to spec isn't exactly what EDID is known for. We're > likely to encounter displays where the DisplayID and EDID contradict > each other, and we'll have to mediate between them. Same here. DisplayID first and treat EDID as legacy. Best regards Thomas > > And what userspace does with all of this is a mess of its own... > > > BR, > Jani. > > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)