On Tuesday, February 28th, 2023 at 09:46, Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > can these be negative as well, to achieve overscan and not just > underscan? Did I get overscan and underscan right... these are related > to under/overscan, aren't they? > > Hmm, no, I guess that doesn't make sense, there is no room in the > signal to have negative margins, it would result in clipping the > framebuffer while scaling up. So this can only be used to scale > framebuffer down, add borders, and the TV then scales it back up > again? Correct. > Looks like neither my Intel nor AMD cards support these, I don't see > the properties. More things to the list of KMS properties Weston needs > to explicitly control. Oh, it seems vc4 exclusive for now. i915 does support it but for TV connectors only (i915/display/intel_tv.c). gud also supports it. > Where does this text appear in the HTML kernel docs? I tried to look at > drm_connector.c but I cannot find the spot where this patch applies. Here: https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#analog-tv-specific-connector-properties > Is this actually a connector property? How does that work, should this > not be a CRTC property? Yeah, it's a connector property for some reason. > Is this instead not scaling anything but simply sending metadata > through the connector? No metadata is sent. This is purely equivalent to setting up CRTC_* properties to scale the planes. > Or are there underlying requirements that this connector property is > actually affecting the CRTC, which means that it is fundamentally > impossible to use multiple connectors with different values on the same > CRTC? And drivers will reject any attempt, so there is no need to > define what conflicting settings will do? I don't think any driver above supports cloning CRTCs for these connector types. i915 sets clonable = false for these connectors. vc4 picks the first connector's TV margins, always. > IOW, does simply the existence of these properties on a connector > guarantee that the connector must be the only one on a CRTC? I suppose that there could exist some hardware capable of applying margins post-CRTC? Such driver could support cloning CRTCs and still applying the connector margins correctly.
