linux-kernel - Re: [PATCH v3 3/4] drm/bridge: Add devm_drm_bridge

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Date:   Mon, 23 May 2022 10:00:39 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Philip Chen <philipchen@...omium.org>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Robert Foss <robert.foss@...aro.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] drm/bridge: Add devm_drm_bridge_add()

Hi,

On Sat, May 21, 2022 at 2:17 AM Maxime Ripard <maxime@...no.tech> wrote:
>
> Hi,
>
> On Tue, May 10, 2022 at 12:29:43PM -0700, Douglas Anderson wrote:
> > This adds a devm managed version of drm_bridge_add(). Like other
> > "devm" function listed in drm_bridge.h, this function takes an
> > explicit "dev" to use for the lifetime management. A few notes:
> > * In general we have a "struct device" for bridges that makes a good
> >   candidate for where the lifetime matches exactly what we want.
> > * The "bridge->dev->dev" device appears to be the encoder
> >   device. That's not the right device to use for lifetime management.
> >
> > Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
>
> If we are to introduce more managed helpers, I think it'd be wiser to
> introduce them as DRM-managed, and not device managed.
>
> Otherwise, you'll end up in a weird state when a device has been removed
> but the DRM device is still around.

I'm kinda confused. In this case there is no DRM device for the bridge
and, as per my CL description, "bridge-dev->dev" appears to be the
encoder device. I wasn't personally involved in discussions about it,
but I was under the impression that this was expected / normal. Thus
we can't make this DRM-managed.

-Doug