linux-kernel - Re: [PATCH] rpi_touchscreen_probe: check for failure case

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Date:   Wed, 24 Jul 2019 07:17:00 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Navid Emamdoost <navid.emamdoost@...il.com>
Cc:     emamd001@....edu, kjlu@....edu, smccaman@....edu,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rpi_touchscreen_probe: check for failure case

Hi Navid.

Thanks for your patch.
On Tue, Jul 23, 2019 at 09:56:43PM -0500, Navid Emamdoost wrote:
> of_graph_get_next_endpoint may return NULL, so null check is needed.
> 
> Signed-off-by: Navid Emamdoost <navid.emamdoost@...il.com>

The patch looks fine, but could you please audit the other calls in the
probe function. For example of_graph_get_remote_port_parent() may also
return NULL.
If you do this then we can have the error handling reviewed in one go,
and fixed in one patch.

	Sam

> ---
>  drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
> index 28c0620dfe0f..2e0977e26fab 100644
> --- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
> +++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
> @@ -399,6 +399,8 @@ static int rpi_touchscreen_probe(struct i2c_client *i2c,
>  
>  	/* Look up the DSI host.  It needs to probe before we do. */
>  	endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
> +	if (!endpoint)
> +		return -ENODEV;
>  	dsi_host_node = of_graph_get_remote_port_parent(endpoint);
>  	host = of_find_mipi_dsi_host_by_node(dsi_host_node);
>  	of_node_put(dsi_host_node);
> -- 
> 2.17.1