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From:   Stephen Boyd <swboyd@chromium.org>
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Date:   Mon, 26 Jul 2021 19:11:59 -0400
Message-ID: <CAE-0n500_tQZK6cDfJgPWO-VWfzW3kj+oS5VEY2EOBHuqv+JHQ@mail.gmail.com>
Subject: Re: [PATCH 1/5] drm/msm/dp: Remove global g_dp_display variable
To:     Abhinav Kumar <abhinavk@codeaurora.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Kalyan Thota <kalyan_t@codeaurora.org>,
        Kuogee Hsieh <khsieh@codeaurora.org>,
        Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>
Cc:     Rob Herring <robh+dt@kernel.org>, linux-arm-msm@vger.kernel.org,
        dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
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Precedence: bulk

Quoting Bjorn Andersson (2021-07-24 21:24:31)
> As the Qualcomm DisplayPort driver only supports a single instance of
> the driver the commonly used struct dp_display is kept in a global
> variable. As we introduce additional instances this obviously doesn't
> work.
>
> Replace this with a combination of existing references to adjacent
> objects and drvdata.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---

Thanks for removing the global.

>  drivers/gpu/drm/msm/dp/dp_display.c | 78 ++++++++++++++---------------
>  1 file changed, 37 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 70b319a8fe83..8696b36d30e4 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -27,7 +27,6 @@
>  #include "dp_audio.h"
>  #include "dp_debug.h"
>
> -static struct msm_dp *g_dp_display;
>  #define HPD_STRING_SIZE 30
>
>  enum {
> @@ -122,6 +121,13 @@ static const struct of_device_id dp_dt_match[] = {
>         {}
>  };
>
> +static struct dp_display_private *dev_to_dp_display_private(struct device *dev)
> +{
> +       struct msm_dp *dp = dev_get_drvdata(dev);
> +
> +       return container_of(dp, struct dp_display_private, dp_display);
> +}
> +
>  static int dp_add_event(struct dp_display_private *dp_priv, u32 event,
>                                                 u32 data, u32 delay)
>  {
> @@ -198,14 +204,16 @@ static int dp_display_bind(struct device *dev, struct device *master,
>                            void *data)
>  {
>         int rc = 0;
> -       struct dp_display_private *dp;
> +       struct dp_display_private *dp = dev_to_dp_display_private(dev);
>         struct drm_device *drm;
>         struct msm_drm_private *priv;
>
>         drm = dev_get_drvdata(master);
>
> -       dp = container_of(g_dp_display,
> -                       struct dp_display_private, dp_display);
> +       if (!dp) {

How can it be NULL? dev_to_dp_display_private() returns container_of()
pointer so it doesn't look possible.

> +               DRM_ERROR("DP driver bind failed. Invalid driver data\n");
> +               return -EINVAL;
> +       }
>
>         dp->dp_display.drm_dev = drm;
>         priv = drm->dev_private;