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

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Message-ID: <CAA8EJpoYJFfB5qfFMoc3-QsmYZzO16C28MOrPyokANQyPBhdyg@mail.gmail.com>
Date:   Tue, 21 Dec 2021 02:53:05 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...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 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?

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


-- 
With best wishes
Dmitry