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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <875xfyedir.fsf@minerva.mail-host-address-is-not-set>
Date: Fri, 11 Jul 2025 21:25:00 +0200
From: Javier Martinez Canillas <javierm@...hat.com>
To: Marcus Folkesson <marcus.folkesson@...il.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

Marcus Folkesson <marcus.folkesson@...il.com> writes:

Hello Marcus,

> Hello Javier,
>
> On Thu, Jul 10, 2025 at 01:00:41PM +0200, Javier Martinez Canillas wrote:
>> >
>> > 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)
>> >
>> 
>> Are you sure about that? As far as I know, that is exactly the
>> difference between gpiod_get() and gpiod_get_optional() variants.
>> 
>> From the gpiod_get_optional() function helper kernel-doc [0]:
>> 
>> /**
>>  * gpiod_get_optional - obtain an optional GPIO for a given GPIO function
>>  * @dev: GPIO consumer, can be NULL for system-global GPIOs
>>  * @con_id: function within the GPIO consumer
>>  * @flags: optional GPIO initialization flags
>>  *
>>  * This is equivalent to gpiod_get(), except that when no GPIO was assigned to
>>  * the requested function it will return NULL. This is convenient for drivers
>>  * that need to handle optional GPIOs.
>>  *
>>  * Returns:
>>  * The GPIO descriptor corresponding to the function @con_id of device
>>  * dev, NULL if no GPIO has been assigned to the requested function, or
>>  * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
>>  */
>> 
>> while the gpiod_get() kernel-doc says the following:
>> 
>> /**
>>  * gpiod_get - obtain a GPIO for a given GPIO function
>>  * @dev:	GPIO consumer, can be NULL for system-global GPIOs
>>  * @con_id:	function within the GPIO consumer
>>  * @flags:	optional GPIO initialization flags
>>  *
>>  * Returns:
>>  * The GPIO descriptor corresponding to the function @con_id of device
>>  * dev, -ENOENT if no GPIO has been assigned to the requested function, or
>>  * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
>>  */
>> 
>
> You are completely righ.
>
> Reviewed-by: Marcus Folkesson <marcus.folkesson@...il.com>
>

Thanks for your review! Do you plan to look at the other patches too ?

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat