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From: Jani Nikula <jani.nikula@linux.intel.com>
To: pengfuyuan <pengfuyuan@kylinos.cn>, Liviu Dudau <liviu.dudau@arm.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard
 <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>, David
 Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
 dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, pengfuyuan
 <pengfuyuan@kylinos.cn>, k2ci <kernel-bot@kylinos.cn>
Subject: Re: [PATCH] arm/komeda: Compile DEFINE_SHOW_ATTRIBUTE() only when
 CONFIG_DEBUG_FS is enabled
In-Reply-To: <20240606075846.1307007-1-pengfuyuan@kylinos.cn>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
References: <20240606075846.1307007-1-pengfuyuan@kylinos.cn>
Date: Thu, 06 Jun 2024 11:20:58 +0300
Message-ID: <87ed9abhxx.fsf@intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain

On Thu, 06 Jun 2024, pengfuyuan <pengfuyuan@kylinos.cn> wrote:
> We do not call komeda_debugfs_init() and the debugfs core function
> declaration if CONFIG_DEBUG_FS is not defined, but we should not
> compile it either because the debugfs core function declaration is
> not included.
>
> Reported-by: k2ci <kernel-bot@kylinos.cn>
> Signed-off-by: pengfuyuan <pengfuyuan@kylinos.cn>

An interesting alternative might actually be to remove *all* the
CONFIG_DEBUG_FS conditional compilation from the file. Since the debugfs
functions have no-op stubs for CONFIG_DEBUG_FS=n, the compiler will
optimize the rest away, because they're no longer referenced. (For the
same reason, I don't think this patch has an impact for code size.)

The upside for removing conditional compilation is that you'll actually
do build testing for both CONFIG_DEBUG_FS config values. Assuming most
developers have it enabled, there's not a lot of testing going on for
CONFIG_DEBUG_FS=n, and you might introduce build failures with the
conditional compilation.

Of course, up to Liviu to decide.


BR,
Jani.


> ---
>  drivers/gpu/drm/arm/display/komeda/komeda_dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> index 14ee79becacb..7ada8e6f407c 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> @@ -21,6 +21,7 @@
>  
>  #include "komeda_dev.h"
>  
> +#ifdef CONFIG_DEBUG_FS
>  static int komeda_register_show(struct seq_file *sf, void *x)
>  {
>  	struct komeda_dev *mdev = sf->private;
> @@ -43,7 +44,6 @@ static int komeda_register_show(struct seq_file *sf, void *x)
>  
>  DEFINE_SHOW_ATTRIBUTE(komeda_register);
>  
> -#ifdef CONFIG_DEBUG_FS
>  static void komeda_debugfs_init(struct komeda_dev *mdev)
>  {
>  	if (!debugfs_initialized())

-- 
Jani Nikula, Intel