Hi, On Thu, Apr 14, 2022 at 12:40 PM Stephen Boyd <swboyd@xxxxxxxxxxxx> wrote: > > Quoting Dmitry Baryshkov (2022-04-14 12:16:14) > > > > I think it's too verbose and a bit incorrect. Not sure which part you're asserting is incorrect, but shorter is OK w/ me too. > > This is a bit saner: > > /* > > * These ops do not make sense for eDP, since they are provided > > * by the panel-bridge corresponding to the attached eDP panel. > > */ > > > > My question was whether we really need to disable them for eDP since for > > eDP the detect and and get_modes will be overridden anyway. Hmm, interesting. Probably for DRM_BRIDGE_OP_MODES that will work? It's definitely worth confirming but from my reading of the code it _probably_ wouldn't hurt. One thing someone would want to confirm would be what would happen if we move this code and the panel code to implement DRM_BRIDGE_OP_EDID properly. It looks as if both actually ought to be implementing that instead of DRM_BRIDGE_OP_MODES, at least in some cases. A fix for a future day. Could we get into trouble if one moved before the other? Then the panel would no longer override the eDP controller and the eDP controller would try to read from a possibly unpowered panel? So I guess in the end my preference would be that we know that driving the EDID read from the controller isn't a great idea for eDP (since we have no way to ensure that the panel is powered) so why risk it and set the bit saying we can do it? For hotplug/detect I'm even less confident that setting the bits would be harmless. I haven't sat down and traced everything, but from what I can see the panel _doesn't_ set these bits, does it? I believe that the rule is that when every bridge in the chain _doesn't_ implement detect/hotplug that the panel is always present. The moment someone says "hey, I can detect" then it suddenly becomes _not_ always present. Yes, I guess we could have the panel implement "detect" and return true, but I'm not convinced that's actually better... > And to go further, I'd expect that a bridge should expose the > functionality that it supports, regardless of what is connected down the > chain. Otherwise we won't be able to mix and match bridges because the > code is brittle, making assumptions about what is connected.
