linux-kernel - Re: [PATCH 2/3] drm/sitronix/st7571-i2c: Make the reset GPIO to be optional

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Message-ID: <aG-aXTgycE4JEJEZ@gmail.com>
Date: Thu, 10 Jul 2025 12:47:57 +0200
From: Marcus Folkesson <marcus.folkesson@...il.com>
To: Javier Martinez Canillas <javierm@...hat.com>
Cc: linux-kernel@...r.kernel.org, ipedrosa@...hat.com,
	David Airlie <airlied@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>, Simona Vetter <simona@...ll.ch>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 2/3] drm/sitronix/st7571-i2c: Make the reset GPIO to be
 optional

On Thu, Jul 10, 2025 at 12:24:34PM +0200, Javier Martinez Canillas wrote:
> Some Sitronix LCD controllers (such as the ST7567) don't have a reset pin,
> so lets relax this in the driver and make the reset GPIO to be optional.
> 
> The devm_gpiod_get_optional() helper is similar to devm_gpiod_get(), but
> returns NULL when there isn't a reset-gpios property defined in a DT node.
> 
> The DT binding schema for "sitronix,st7571" that require a reset GPIO will
> enforce the "reset-gpios" to be present, due being a required DT property.
> But in the driver itself the property can be made optional if not defined.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> ---
> 
>  drivers/gpu/drm/sitronix/st7571-i2c.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sitronix/st7571-i2c.c b/drivers/gpu/drm/sitronix/st7571-i2c.c
> index eec846892962..73e8db25f895 100644
> --- a/drivers/gpu/drm/sitronix/st7571-i2c.c
> +++ b/drivers/gpu/drm/sitronix/st7571-i2c.c
> @@ -802,15 +802,19 @@ static int st7571_parse_dt(struct st7571_device *st7571)
>  	st7571->nlines = dt.vactive.typ;
>  	st7571->ncols = dt.hactive.typ;
>  
> -	st7571->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> +	st7571->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
>  	if (IS_ERR(st7571->reset))
> -		return PTR_ERR(st7571->reset);
> +		return dev_err_probe(dev, PTR_ERR(st7571->reset),
> +				     "Failed to get reset gpio\n");

devm_gpiod_get_optional() returns -ENOENT when the GPIO is not found,
and that is no error we want to propagage upwards.

Maybe something like this instead:
if (IS_ERR(st7571->reset) && IS_ERR(st7571->reset) != -ENOENT)


Best regards,
Marcus Folkesson

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