linux-kernel - Re: [PATCH v2] drm: of: Properly try all possible cases for bridge/panel detection

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Message-ID: <20220318161847.ezi6yat4on7rvfdf@houat>
Date:   Fri, 18 Mar 2022 17:18:47 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2] drm: of: Properly try all possible cases for
 bridge/panel detection

On Fri, Mar 18, 2022 at 05:02:49PM +0100, Paul Kocialkowski wrote:
> While bridge/panel detection was initially relying on the usual
> port/ports-based of graph detection, it was recently changed to
> perform the lookup on any child node that is not port/ports
> instead when such a node is available, with no fallback on the
> usual way.
> 
> This results in breaking detection when a child node is present
> but does not contain any panel or bridge node, even when the
> usual port/ports-based of graph is there.
> 
> In order to support both situations properly, this commit reworks
> the logic to try both options and not just one of the two: it will
> only return -EPROBE_DEFER when both have failed.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> Fixes: 80253168dbfd ("drm: of: Lookup if child node has panel or bridge")
> ---
> 
> Changes since v1:
> - Renamed remote to node;
> - Renamed helper to find_panel_or_bridge;
> - Cleared bridge pointer early;
> - Returned early to make the code more concise;
> 
> ---
>  drivers/gpu/drm/drm_of.c | 98 ++++++++++++++++++++--------------------
>  1 file changed, 49 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index 9d90cd75c457..63137c833b7a 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -219,6 +219,28 @@ int drm_of_encoder_active_endpoint(struct device_node *node,
>  }
>  EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);
>  
> +static int find_panel_or_bridge(struct device_node *node,
> +				struct drm_panel **panel,
> +				struct drm_bridge **bridge)
> +{
> +	if (panel) {
> +		*panel = of_drm_find_panel(node);
> +		if (!IS_ERR(*panel))
> +			return 0;
> +		else
> +			*panel = NULL;

You don't need the else branch here, we already cleared panel in
drm_of_find_panel_or_bridge

Looks good otherwise, thanks!
Maxime

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