linux-kernel - Re: [PATCH] drm/i915/display: Remove kstrdup_const() and kfree

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Message-ID: <87h69srz1q.fsf@intel.com>
Date: Fri, 04 Oct 2024 12:35:13 +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,
 Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 intel-gfx@...ts.freedesktop.org, intel-xe@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/i915/display: Remove kstrdup_const() and
 kfree_const() usage

On Thu, 03 Oct 2024, Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:
> kstrdup_const() and kfree_const() can be confusing in code built as a
> module. In such a case, it does not do what one could expect from the name
> of the functions.
>
> The code is not wrong by itself, but in such a case, it is equivalent to
> kstrdup() and kfree().
>
> So, keep thinks simple and straightforward.
>
> This reverts commit 379b63e7e682 ("drm/i915/display: Save a few bytes of
> memory in intel_backlight_device_register()")

Sorry, I guess I'm confused here. Or I just didn't read the commit
message to [1] properly. Or both.

So the whole point of [1] was that the _const versions can be confusing
if i915 is builtin? But not wrong?

BR,
Jani.


[1] https://lore.kernel.org/r/3b3d3af8739e3016f3f80df0aa85b3c06230a385.1727533674.git.christophe.jaillet@wanadoo.fr



>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
>  drivers/gpu/drm/i915/display/intel_backlight.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c
> index 9e05745d797d..3f81a726cc7d 100644
> --- a/drivers/gpu/drm/i915/display/intel_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_backlight.c
> @@ -949,7 +949,7 @@ int intel_backlight_device_register(struct intel_connector *connector)
>  	else
>  		props.power = BACKLIGHT_POWER_OFF;
>  
> -	name = kstrdup_const("intel_backlight", GFP_KERNEL);
> +	name = kstrdup("intel_backlight", GFP_KERNEL);
>  	if (!name)
>  		return -ENOMEM;
>  
> @@ -963,7 +963,7 @@ int intel_backlight_device_register(struct intel_connector *connector)
>  		 * compatibility. Use unique names for subsequent backlight devices as a
>  		 * fallback when the default name already exists.
>  		 */
> -		kfree_const(name);
> +		kfree(name);
>  		name = kasprintf(GFP_KERNEL, "card%d-%s-backlight",
>  				 i915->drm.primary->index, connector->base.name);
>  		if (!name)
> @@ -987,7 +987,7 @@ int intel_backlight_device_register(struct intel_connector *connector)
>  		    connector->base.base.id, connector->base.name, name);
>  
>  out:
> -	kfree_const(name);
> +	kfree(name);
>  
>  	return ret;
>  }

-- 
Jani Nikula, Intel