linux-kernel - Re: [PATCH v2] drm/msm/dp: Only create debugfs for PRIMARY minor

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Message-ID: <YcEZljENYJQAk9We@ripper>
Date:   Mon, 20 Dec 2021 16:02:30 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm/dp: Only create debugfs for PRIMARY minor

On Mon 20 Dec 15:53 PST 2021, Dmitry Baryshkov wrote:

> On Fri, 17 Dec 2021 at 03:19, Bjorn Andersson
> <bjorn.andersson@...aro.org> wrote:
> >
> > dpu_kms_debugfs_init() is invoked for each minor being registered. Most
> > of the files created are unrelated to the minor, so there's no reason to
> > present them per minor.
> > The exception to this is the DisplayPort code, which ends up invoking
> > dp_debug_get() for each minor, each time associate the allocated object
> > with dp->debug.
> >
> > As such dp_debug will create debugfs files in both the PRIMARY and the
> > RENDER minor's debugfs directory, but only the last reference will be
> > remembered.
> >
> > The only use of this reference today is in the cleanup path in
> > dp_display_deinit_sub_modules() and the dp_debug_private object does
> > outlive the debugfs entries in either case, so there doesn't seem to be
> > any adverse effects of this, but per the code the current behavior is
> > unexpected, so change it to only create debugfs files for the PRIMARY
> > minor.
> >
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > ---
> >
> > Changes since v1:
> > - Moved the check up from msm_dp_debugfs_init() to dpu_kms_debugfs_init()
> >
> >  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > index 2ee70072a1b4..a54f7d373f14 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > @@ -193,6 +193,10 @@ static int dpu_kms_debugfs_init(struct msm_kms *kms, struct drm_minor *minor)
> >         if (!p)
> >                 return -EINVAL;
> >
> > +       /* Only create one set of debugfs per DP instance */
> 
> The comment is misleading. Could you please fix it?
> 

I agree, and as Abhinav pointed out I didn't update $subject fully
either.

Will resubmit.

Regards,
Bjorn

> > +       if (minor->type != DRM_MINOR_PRIMARY)
> > +               return 0;
> > +
> >         dev = dpu_kms->dev;
> >         priv = dev->dev_private;
> >
> > --
> > 2.33.1
> >
> 
> 
> -- 
> With best wishes
> Dmitry