linux-kernel - Re: [PATCH v2] drm/msm: use compatible lists to find mdp node

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Date:   Tue, 19 Oct 2021 23:23:01 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Krishna Manikandan <mkrishn@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     kalyan_t@...eaurora.org, robdclark@...il.com,
        freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2] drm/msm: use compatible lists to find mdp node

Quoting Krishna Manikandan (2021-10-18 22:30:28)
> In the current implementation, substring comparison
> using device node name is used to find mdp node
> during driver probe. Use compatible string list instead
> of node name to get mdp node from the parent mdss node.
>
> Signed-off-by: Krishna Manikandan <mkrishn@...eaurora.org>
>
> Changes in v2:
>    - Use compatible lists instead of duplicate string
>      check (Stephen Boyd)
> ---
>  drivers/gpu/drm/msm/msm_drv.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 2e6fc18..451d667 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -1241,9 +1241,13 @@ static int add_components_mdp(struct device *mdp_dev,
>         return 0;
>  }
>
> -static int compare_name_mdp(struct device *dev, void *data)
> +static int find_mdp_node(struct device *dev, void *data)
>  {
> -       return (strstr(dev_name(dev), "mdp") != NULL);
> +       if (!dev->driver)

I don't think we want to wait for the device to have an attached driver.
That could be far later than when we're trying to add all the
components here. Can you reference the match tables directly?


> +               return 0;
> +
> +       return (of_match_node(dev->driver->of_match_table,
> +                               dev->of_node) != NULL);

Drop useless parenthesis.

>  }
>
>  static int add_display_components(struct platform_device *pdev,
> @@ -1268,7 +1272,7 @@ static int add_display_components(struct platform_device *pdev,
>                         return ret;
>                 }
>
> -               mdp_dev = device_find_child(dev, NULL, compare_name_mdp);
> +               mdp_dev = device_find_child(dev, NULL, find_mdp_node);
>                 if (!mdp_dev) {
>                         DRM_DEV_ERROR(dev, "failed to find MDSS MDP node\n");
>                         of_platform_depopulate(dev);