[v2,2/2] drm/i915/fbc: Avoid full proxy f_ops for FBC debug attributes

  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>
---
Changes in v2:
   - Include coccicheck make command in the patch log message for clarity.
     Suggested by Rodrigo Vivi <rodrigo.vivi@intel.com>


 drivers/gpu/drm/i915/display/intel_fbc.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)
  

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@mailo.com>

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

On Tue, Jan 10, 2023 at 01:52:05PM -0500, Rodrigo Vivi wrote:
> 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@mailo.com>
> 
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> 
> (Are you planning to send the one for pxp file?)

Hello Rodrigo,
The pxp file is implemented differently using a common function for another SHOW
attribute file. I am exploring how to best handle that and would send in a patch
if feasible. See the simplified code snip below:

	static const struct intel_gt_debugfs_file files[] = {
		{ "info", &pxp_info_fops, NULL },
		{ "terminate_state", &pxp_terminate_fops, NULL },
	};
	...
	intel_gt_debugfs_register_files(root, files, ARRAY_SIZE(files), pxp);

Thank you.
./drv

> 
> > ---
> > Changes in v2:
> >    - Include coccicheck make command in the patch log message for clarity.
> >      Suggested by Rodrigo Vivi <rodrigo.vivi@intel.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
> > 
> > 
> >