linux-kernel - Re: [PATCH] drm/i915/backlight: Remove a useless kstrdup

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Message-ID: <87cykiu3hk.fsf@intel.com>
Date: Wed, 02 Oct 2024 14:51:51 +0300
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>, Rodrigo Vivi
 <rodrigo.vivi@...el.com>, Joonas Lahtinen
 <joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
 intel-gfx@...ts.freedesktop.org, intel-xe@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/i915/backlight: Remove a useless kstrdup_const()

On Tue, 01 Oct 2024, Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:
> Le 30/09/2024 à 09:48, Jani Nikula a écrit :
>> On Sat, 28 Sep 2024, Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:
>>> "name" is allocated and freed in intel_backlight_device_register().
>>> The initial allocation just duplicates "intel_backlight".
>>>
>>> Later, if a device with this name has already been registered, another
>>> dynamically generated one is allocated using kasprintf().
>>>
>>> So at the end of the function, when "name" is freed, it can point either to
>>> the initial static literal "intel_backlight" or to the kasprintf()'ed one.
>>>
>>> So kfree_const() is used.
>>>
>>> However, when built as a module, kstrdup_const() and kfree_const() don't
>>> work as one would expect and are just plain kstrdup() and kfree().
>>>
>>>
>>> Slightly change the logic and introduce a new variable to hold the
>>> address returned by kasprintf() should it be used.
>>>
>>> This saves a memory allocation/free and avoids these _const functions,
>>> which names can be confusing when used with code built as module.
>> 
>> Okay, I'd rather revert your earlier commit 379b63e7e682
>> ("drm/i915/display: Save a few bytes of memory in
>> intel_backlight_device_register()") than add this.
>
> Hi,
>
> that works for me. Thanks and sorry for the noise.

Will you send the revert?

BR,
Jani.


-- 
Jani Nikula, Intel