From: Doug Anderson <dianders@chromium.org>
To: Brian Norris <briannorris@chromium.org>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>,
Jonas Karlman <jonas@kwiboo.se>,
dri-devel <dri-devel@lists.freedesktop.org>,
Neil Armstrong <narmstrong@baylibre.com>,
LKML <linux-kernel@vger.kernel.org>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
Andrzej Hajda <a.hajda@samsung.com>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
"open list:ARM/Rockchip SoC..."
<linux-rockchip@lists.infradead.org>,
"# 4.0+" <stable@vger.kernel.org>, Sean Paul <sean@poorly.run>
Subject: Re: [PATCH v2] drm/bridge: analogix_dp: Grab runtime PM reference for DP-AUX
Date: Wed, 16 Feb 2022 10:10:16 -0800 [thread overview]
Message-ID: <CAD=FV=XivCxy-7Wszv9pnHELi=gRCMeVasEweza17XTtEoiT4A@mail.gmail.com> (raw)
In-Reply-To: <CA+ASDXO8c4dK31p=kvBABJQsDUs20qVHM6NxYf1JQDCr2oswAw@mail.gmail.com>
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-interface
>
> 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.
prev parent reply other threads:[~2022-02-16 18:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-01 21:42 [PATCH v2] drm/bridge: analogix_dp: Grab runtime PM reference for DP-AUX Brian Norris
2022-01-05 19:55 ` Brian Norris
2022-01-11 13:26 ` Andrzej Hajda
2022-01-11 19:17 ` Brian Norris
2022-02-15 21:31 ` Doug Anderson
2022-02-15 22:51 ` Brian Norris
2022-02-15 23:46 ` Doug Anderson
2022-02-16 0:40 ` Brian Norris
2022-02-16 18:10 ` Doug Anderson [this message]
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