Date:   Sun, 22 Jan 2023 23:52:18 +0530
From:   Deepak R Varma <drv@mailo.com>
To:     Alain Volmat <alain.volmat@foss.st.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Cc:     Saurabh Singh Sengar <ssengar@microsoft.com>,
        Praveen Kumar <kumarpraveen@linux.microsoft.com>
Subject: Re: [PATCH] drm/sti: Avoid full proxy f_ops for sti debug attributes
Message-ID: <Y81+2gAtmPW2n0gS@ubun2204.myguest.virtualbox.org>
References: <Y73IdsbXhB5aUrkP@ubun2204.myguest.virtualbox.org>
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On Wed, Jan 11, 2023 at 01:50:06AM +0530, Deepak R Varma wrote:
> Using DEFINE_SIMPLE_ATTRIBUTE macro with the debugfs_create_file()
> function adds the overhead of introducing a proxy file operation
> functions to wrap the original read/write inside file removal protection
> functions. This adds significant overhead in terms of introducing and
> managing the proxy factory file operations structure and function
> wrapping at runtime.
> As a replacement, a combination of DEFINE_DEBUGFS_ATTRIBUTE macro paired
> with debugfs_create_file_unsafe() is suggested to be used instead.  The
> DEFINE_DEBUGFS_ATTRIBUTE utilises debugfs_file_get() and
> debugfs_file_put() wrappers to protect the original read and write
> function calls for the debug attributes. There is no need for any
> runtime proxy file operations to be managed by the debugfs core.
> Following coccicheck make command helped identify this change:
> 
> make coccicheck M=drivers/gpu/drm/i915/ MODE=patch COCCI=./scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci
> 
> Signed-off-by: Deepak R Varma <drv@mailo.com>
> ---
> Note: Change cross compile tested using stm32_defconfig for arm

Hello,
Is there a feedback/comment on this patch proposal please? Let me know if I
should resend it.

Thank you,
./drv

> 
>  drivers/gpu/drm/sti/sti_drv.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sti/sti_drv.c b/drivers/gpu/drm/sti/sti_drv.c
> index ef6a4e63198f..c9be82043638 100644
> --- a/drivers/gpu/drm/sti/sti_drv.c
> +++ b/drivers/gpu/drm/sti/sti_drv.c
> @@ -67,8 +67,8 @@ static int sti_drm_fps_set(void *data, u64 val)
>  	return 0;
>  }
>  
> -DEFINE_SIMPLE_ATTRIBUTE(sti_drm_fps_fops,
> -			sti_drm_fps_get, sti_drm_fps_set, "%llu\n");
> +DEFINE_DEBUGFS_ATTRIBUTE(sti_drm_fps_fops,
> +			 sti_drm_fps_get, sti_drm_fps_set, "%llu\n");
>  
>  static int sti_drm_fps_dbg_show(struct seq_file *s, void *data)
>  {
> @@ -97,8 +97,8 @@ static void sti_drm_dbg_init(struct drm_minor *minor)
>  				 ARRAY_SIZE(sti_drm_dbg_list),
>  				 minor->debugfs_root, minor);
>  
> -	debugfs_create_file("fps_show", S_IRUGO | S_IWUSR, minor->debugfs_root,
> -			    minor->dev, &sti_drm_fps_fops);
> +	debugfs_create_file_unsafe("fps_show", S_IRUGO | S_IWUSR, minor->debugfs_root,
> +				   minor->dev, &sti_drm_fps_fops);
>  
>  	DRM_INFO("%s: debugfs installed\n", DRIVER_NAME);
>  }
> -- 
> 2.34.1
> 
> 
>