linux-kernel - Re: [PATCH v2 3/5] drm/panel: panel-simple: Make panel_simple

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Message-ID: <875xghczxe.fsf@minerva.mail-host-address-is-not-set>
Date: Fri, 27 Jun 2025 11:10:53 +0200
From: Javier Martinez Canillas <javierm@...hat.com>
To: Maxime Ripard <mripard@...nel.org>, Neil Armstrong
 <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann
 <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter
 <simona@...ll.ch>, Luca Ceresoli <luca.ceresoli@...tlin.com>, Anusha
 Srivatsa <asrivats@...hat.com>, Francesco Dolcini <francesco@...cini.it>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, Maxime
 Ripard <mripard@...nel.org>
Subject: Re: [PATCH v2 3/5] drm/panel: panel-simple: Make panel_simple_probe
 return its panel

Maxime Ripard <mripard@...nel.org> writes:

> In order to fix the regession introduced by commit de04bb0089a9
> ("drm/panel/panel-simple: Use the new allocation in place of
> devm_kzalloc()"), we need to move the panel_desc lookup into the common
> panel_simple_probe() function.
>
> There's two callers for that function, the probe implementations of the
> platform and MIPI-DSI drivers panel-simple implements.
>
> The MIPI-DSI driver's probe will need to access the current panel_desc
> to initialize properly, which won't be possible anymore if we make that
> lookup in panel_simple_probe().
>
> However, we can make panel_simple_probe() return the initialized
> panel_simple structure it allocated, which will contain a pointer to the
> associated panel_desc in its desc field.
>
> This doesn't fix de04bb0089a9 ("drm/panel/panel-simple: Use the new
> allocation in place of devm_kzalloc()") still, but makes progress
> towards that goal.
>
> Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---

[...]

> -static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
> +static struct panel_simple *panel_simple_probe(struct device *dev, const struct panel_desc *desc)
>  {

[...]

>  
>  	ddc = of_parse_phandle(dev->of_node, "ddc-i2c-bus", 0);
>  	if (ddc) {
>  		panel->ddc = of_find_i2c_adapter_by_node(ddc);
>  		of_node_put(ddc);
>  
>  		if (!panel->ddc)
> -			return -EPROBE_DEFER;
> +			return ERR_PTR(-EPROBE_DEFER);

Not related with your patch, but it would be great to also add a
dev_err_probe() here to record the reason of this probe deferral.

Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat