linux-kernel - Re: [PATCH] drm: bridge: remove error message for EPROBE_DEFER in bridge

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Message-ID: <Yanj7O9Kktw8PPY1@pendragon.ideasonboard.com>
Date:   Fri, 3 Dec 2021 11:31:24 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Yannick Fertre <yannick.fertre@...s.st.com>
Cc:     Philippe Cornu <philippe.cornu@...s.st.com>,
        Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: bridge: remove error message for EPROBE_DEFER in
 bridge_attach

Hi Yannick,

Thank you for the patch.

On Fri, Dec 03, 2021 at 09:59:31AM +0100, Yannick Fertre wrote:
> Probe deferred is not an error, don't print it.
> 
> Signed-off-by: Yannick Fertre <yannick.fertre@...s.st.com>
> ---
>  drivers/gpu/drm/drm_bridge.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index c96847fc0ebc..cef0a62ef5d0 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -288,11 +288,13 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>  	list_del(&bridge->chain_node);
>  
>  #ifdef CONFIG_OF
> -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> -		  bridge->of_node, encoder->name, ret);
> +	if (ret != -EPROBE_DEFER)
> +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> +			  bridge->of_node, encoder->name, ret);
>  #else
> -	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> -		  encoder->name, ret);
> +	if (ret != -EPROBE_DEFER)
> +		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> +			  encoder->name, ret);

It's useful to know about what caused a probe deferral though. There's
now a dev_err_probe() function that prints the message as an dev_err if
the error code is not -EPROBE_DEFER, and as dev_dbg otherwise. It's
meant for probe time only though, so I don't think it can be used here,
but a similar feature could be useful. Or dev_err_probe() could be
extended to support non-probe use cases, but that would be more
difficult.

>  #endif
>  
>  	return ret;

-- 
Regards,

Laurent Pinchart