Hi,
On Tue, Feb 15, 2022 at 4:41 PM Brian Norris briannorris@chromium.org wrote:
On Tue, Feb 15, 2022 at 3:46 PM Doug Anderson dianders@chromium.org wrote:
On Tue, Feb 15, 2022 at 2:52 PM Brian Norris briannorris@chromium.org wrote:
It still makes me wonder what the point of the /dev/drm_dp_aux<N> interface is though, because it seems like you're pretty much destined to not have reliable operation through that means.
I can't say I have tons of history for those files. I seem to recall maybe someone using them to have userspace tweak the embedded backlight on some external DP connected panels? I think we also might use it in Chrome OS to update the firmware of panels (dunno if internal or external) in some cases too? I suspect that it works OK for certain situations but it's really not going to work in all cases...
Yes, I believe I'm only submitting patches like this because fwupd apparently likes to indiscriminately whack at dpaux devices: https://github.com/fwupd/fwupd/tree/main/plugins/synaptics-mst#kernel-dp-aux...
That seems like a bad idea.
(We've already disabled that plugin on these systems, but it seems wise not to leave the stumbling block here for the next time.)
Yeah, it doesn't seem great. I guess it's _slightly_ less bad since it's for an external device. As I understand it, they never really turn off in the same way. It still feels like letting userspace indiscriminately whack at DP AUX registers isn't a great idea, though.