linux-kernel - Re: [Intel-gfx] [PATCH v2 1/2] drm/i915/display: Avoid full proxy f

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Message-ID: <Y72zsk1eAmROtU9B@intel.com>
Date:   Tue, 10 Jan 2023 13:51:30 -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: [Intel-gfx] [PATCH v2 1/2] drm/i915/display: Avoid full proxy
 f_ops for DRRS debug attributes

On Tue, Jan 10, 2023 at 11:45:02PM +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>
> ---
> Changes in v2:
>    - Include coccicheck make command in the patch log message for clarity.
>      Suggested by Rodrigo Vivi <rodrigo.vivi@...el.com>

Thank you

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

> 
>  drivers/gpu/drm/i915/display/intel_drrs.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_drrs.c b/drivers/gpu/drm/i915/display/intel_drrs.c
> index 5b9e44443814..84ba7379d6f8 100644
> --- a/drivers/gpu/drm/i915/display/intel_drrs.c
> +++ b/drivers/gpu/drm/i915/display/intel_drrs.c
> @@ -374,16 +374,16 @@ static int intel_drrs_debugfs_ctl_set(void *data, u64 val)
>  	return ret;
>  }
>  
> -DEFINE_SIMPLE_ATTRIBUTE(intel_drrs_debugfs_ctl_fops,
> -			NULL, intel_drrs_debugfs_ctl_set, "%llu\n");
> +DEFINE_DEBUGFS_ATTRIBUTE(intel_drrs_debugfs_ctl_fops,
> +			 NULL, intel_drrs_debugfs_ctl_set, "%llu\n");
>  
>  void intel_drrs_crtc_debugfs_add(struct intel_crtc *crtc)
>  {
>  	debugfs_create_file("i915_drrs_status", 0444, crtc->base.debugfs_entry,
>  			    crtc, &intel_drrs_debugfs_status_fops);
>  
> -	debugfs_create_file("i915_drrs_ctl", 0644, crtc->base.debugfs_entry,
> -			    crtc, &intel_drrs_debugfs_ctl_fops);
> +	debugfs_create_file_unsafe("i915_drrs_ctl", 0644, crtc->base.debugfs_entry,
> +				    crtc, &intel_drrs_debugfs_ctl_fops);
>  }
>  
>  static int intel_drrs_debugfs_type_show(struct seq_file *m, void *unused)
> -- 
> 2.34.1
> 
> 
>