linux-kernel - Re: [PATCH] drm/panel: novatek-nt35950: Improve error handling

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Date:   Mon, 17 Apr 2023 09:25:43 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Marijn Suijten <marijn.suijten@...ainline.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panel: novatek-nt35950: Improve error handling

On 15/04/2023 13:00, Konrad Dybcio wrote:
> In a very peculiar case when probing and registering with the secondary
> DSI host succeeds, but the OF backlight or DSI attachment fails, the
> primary DSI device is automatically cleaned up, but the secondary one
> is not, leading to -EEXIST when the driver core tries to handle
> -EPROBE_DEFER.
> 
> Unregister the DSI1 device manually on failure to prevent that.
> 
> Fixes: 623a3531e9cf ("drm/panel: Add driver for Novatek NT35950 DSI DriverIC panels")
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>   drivers/gpu/drm/panel/panel-novatek-nt35950.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-novatek-nt35950.c b/drivers/gpu/drm/panel/panel-novatek-nt35950.c
> index abf752b36a52..7498fc6258bb 100644
> --- a/drivers/gpu/drm/panel/panel-novatek-nt35950.c
> +++ b/drivers/gpu/drm/panel/panel-novatek-nt35950.c
> @@ -585,8 +585,11 @@ static int nt35950_probe(struct mipi_dsi_device *dsi)
>   		       DRM_MODE_CONNECTOR_DSI);
>   
>   	ret = drm_panel_of_backlight(&nt->panel);
> -	if (ret)
> +	if (ret) {
> +		mipi_dsi_device_unregister(nt->dsi[1]);
> +
>   		return dev_err_probe(dev, ret, "Failed to get backlight\n");
> +	}
>   
>   	drm_panel_add(&nt->panel);
>   
> @@ -602,6 +605,9 @@ static int nt35950_probe(struct mipi_dsi_device *dsi)
>   
>   		ret = mipi_dsi_attach(nt->dsi[i]);
>   		if (ret < 0) {
> +			/* If we fail to attach to either host, we're done */
> +			mipi_dsi_device_unregister(nt->dsi[1]);
> +
>   			return dev_err_probe(dev, ret,
>   					     "Cannot attach to DSI%d host.\n", i);
>   		}
> 
> ---
> base-commit: 035ba5f9cf511b9299fd9c9d0688ef930d33c886
> change-id: 20230415-konrad-longbois-next-847d57abb4d2
> 
> Best regards,

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>