linux-kernel - Re: [PATCH v2 2/2] drm/i915/fbc: Avoid full proxy f

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Message-ID: <Y72z1T1bifo3YpSR@intel.com>
Date:   Tue, 10 Jan 2023 13:52:05 -0500
From:   Rodrigo Vivi <rodrigo.vivi@...el.com>
To:     Deepak R Varma <drv@...lo.com>
CC:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        "Daniel Vetter" <daniel@...ll.ch>,
        <intel-gfx@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        "Praveen Kumar" <kumarpraveen@...ux.microsoft.com>,
        Saurabh Singh Sengar <ssengar@...rosoft.com>
Subject: Re: [PATCH v2 2/2] drm/i915/fbc: Avoid full proxy f_ops for FBC
 debug attributes

On Tue, Jan 10, 2023 at 11:45:40PM +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@...lo.com>

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>

(Are you planning to send the one for pxp file?)

> ---
> Changes in v2:
>    - Include coccicheck make command in the patch log message for clarity.
>      Suggested by Rodrigo Vivi <rodrigo.vivi@...el.com>
> 
> 
>  drivers/gpu/drm/i915/display/intel_fbc.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
> index 5e69d3c11d21..c508dcf415b4 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> @@ -1807,10 +1807,10 @@ static int intel_fbc_debugfs_false_color_set(void *data, u64 val)
>  	return 0;
>  }
>  
> -DEFINE_SIMPLE_ATTRIBUTE(intel_fbc_debugfs_false_color_fops,
> -			intel_fbc_debugfs_false_color_get,
> -			intel_fbc_debugfs_false_color_set,
> -			"%llu\n");
> +DEFINE_DEBUGFS_ATTRIBUTE(intel_fbc_debugfs_false_color_fops,
> +			 intel_fbc_debugfs_false_color_get,
> +			 intel_fbc_debugfs_false_color_set,
> +			 "%llu\n");
>  
>  static void intel_fbc_debugfs_add(struct intel_fbc *fbc,
>  				  struct dentry *parent)
> @@ -1819,8 +1819,8 @@ static void intel_fbc_debugfs_add(struct intel_fbc *fbc,
>  			    fbc, &intel_fbc_debugfs_status_fops);
>  
>  	if (fbc->funcs->set_false_color)
> -		debugfs_create_file("i915_fbc_false_color", 0644, parent,
> -				    fbc, &intel_fbc_debugfs_false_color_fops);
> +		debugfs_create_file_unsafe("i915_fbc_false_color", 0644, parent,
> +					   fbc, &intel_fbc_debugfs_false_color_fops);
>  }
>  
>  void intel_fbc_crtc_debugfs_add(struct intel_crtc *crtc)
> -- 
> 2.34.1
> 
> 
>