linux-kernel - Re: [PATCH v5 2/6] drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

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Message-ID: <20200506164133.GB19296@ravnborg.org>
Date:   Wed, 6 May 2020 18:41:33 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-tegra@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v5 2/6] drm/of: Make drm_of_find_panel_or_bridge() to
 check graph's presence

On Sat, Apr 18, 2020 at 08:06:59PM +0300, Dmitry Osipenko wrote:
> When graph isn't defined in a device-tree, the of_graph_get_remote_node()
> prints a noisy error message, telling that port node is not found. This is
> undesirable behaviour in our case because absence of a panel/bridge graph
> is a valid case. Let's check presence of the local port in a device-tree
> before proceeding with parsing the graph.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
Reviewed-by: Sam Ravnborg <sam@...nborg.org>
> ---
>  drivers/gpu/drm/drm_of.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index b50b44e76279..e0652c38f357 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -239,13 +239,24 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>  				struct drm_bridge **bridge)
>  {
>  	int ret = -EPROBE_DEFER;
> -	struct device_node *remote;
> +	struct device_node *local, *remote;
>  
>  	if (!panel && !bridge)
>  		return -EINVAL;
>  	if (panel)
>  		*panel = NULL;
>  
> +	/*
> +	 * of_graph_get_remote_node() produces a noisy error message if port
> +	 * node isn't found and the absence of the port is a legit case here,
> +	 * so at first we silently check presence of the local port.
> +	 */
> +	local = of_graph_get_local_port(np);
> +	if (!local)
> +		return -ENODEV;
> +
> +	of_node_put(local);
> +
>  	remote = of_graph_get_remote_node(np, port, endpoint);
>  	if (!remote)
>  		return -ENODEV;
> -- 
> 2.26.0
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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