On Tue, Sep 23, 2014 at 12:40:24PM +0300, Tomi Valkeinen wrote: > On 23/09/14 11:35, Thierry Reding wrote: > > > Well, a display controller is never going to attach to a panel directly. > > With parallel RGB, that (almost) happens. There's voltage level shifting > probably in the middle, but I don't see anything else there. The level shifting could be considered an encoder. Anyway, I didn't mean physically attach to a panel but rather in DRM. You'll always need an encoder and connector before you go to the panel. > > But I agree that it would be nice to unify bridges and encoders more. It > > should be possible to make encoder always a bridge (or perhaps even > > replace encoders with bridges altogether). Then once you're out of the > > DRM device everything would be a bridge until you get to a panel. > > What exactly is a bridge and what is an encoder? Those are DRM > constructs, aren't they? Yes. I think bridges are mostly a superset of encoders. > As I see it, a video pipeline consist of a video source (display > controller usually), a chain of encoders (all of which may not be > strictly "encoders", they could be level shifters, muxes, ESD protection > devices or such), and either a display device like a panel or a > connector to outside world. Well, the panel itself is attached to a connector. The connector is really what userspace uses to control the output and indirectly the panel. > Am I right that in DRM world the encoder is the first device in the > display chain after the display controller, Yes. > and the next is a bridge? A bridge or a connector. Typically it would be a connector, but that's only if you don't have bridges in between. > That sounds totally artificial, and I hope we don't reflect that in the > DT side in any way. Yes, they are software concepts and I'm not aware of any of it being exposed in DT. A display controller is usually implemented as DRM CRTC object and outputs (DSI, eDP, HDMI) as encoder (often with a connector tied to it). Thierry
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