[PATCH] omapdrm: no need to check return value of debugfs_create functions

[PATCH] omapdrm: no need to check return value of debugfs_create functions

[Greg Kroah-Hartman]

When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Sebastian Reichel <sebastian.reichel@collabora.com>
Cc: Jyri Sarha <jsarha@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: zhong jiang <zhongjiang@huawei.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/omapdrm/dss/dss.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/dss/dss.c b/drivers/gpu/drm/omapdrm/dss/dss.c
index 55e68863ef15..83b973813394 100644
--- a/drivers/gpu/drm/omapdrm/dss/dss.c
+++ b/drivers/gpu/drm/omapdrm/dss/dss.c
@@ -934,7 +934,6 @@ dss_debugfs_create_file(struct dss_device *dss, const char *name,
 			void *data)
 {
 	struct dss_debugfs_entry *entry;
-	struct dentry *d;
 
 	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 	if (!entry)
@@ -942,15 +941,9 @@ dss_debugfs_create_file(struct dss_device *dss, const char *name,
 
 	entry->show_fn = show_fn;
 	entry->data = data;
+	entry->dentry = debugfs_create_file(name, 0444, dss->debugfs.root,
+					    entry, &dss_debug_fops);
 
-	d = debugfs_create_file(name, 0444, dss->debugfs.root, entry,
-				&dss_debug_fops);
-	if (IS_ERR(d)) {
-		kfree(entry);
-		return ERR_CAST(d);
-	}
-
-	entry->dentry = d;
 	return entry;
 }
 
-- 
2.22.0

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Re: [PATCH] omapdrm: no need to check return value of debugfs_create functions

[Laurent Pinchart]

Hi Greg,

Thank you for the patch.

On Thu, Jun 13, 2019 at 01:57:49PM +0200, Greg Kroah-Hartman wrote:
> When calling debugfs functions, there is no need to ever check the
> return value.  The function can work or not, but the code logic should
> never do something different based on this.
> 
> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Sebastian Reichel <sebastian.reichel@collabora.com>
> Cc: Jyri Sarha <jsarha@ti.com>
> Cc: Tony Lindgren <tony@atomide.com>
> Cc: zhong jiang <zhongjiang@huawei.com>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This makes sense.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Tomi, will you take this patch in your tree ?

> ---
>  drivers/gpu/drm/omapdrm/dss/dss.c | 11 ++---------
>  1 file changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/dss.c b/drivers/gpu/drm/omapdrm/dss/dss.c
> index 55e68863ef15..83b973813394 100644
> --- a/drivers/gpu/drm/omapdrm/dss/dss.c
> +++ b/drivers/gpu/drm/omapdrm/dss/dss.c
> @@ -934,7 +934,6 @@ dss_debugfs_create_file(struct dss_device *dss, const char *name,
>  			void *data)
>  {
>  	struct dss_debugfs_entry *entry;
> -	struct dentry *d;
>  
>  	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
>  	if (!entry)
> @@ -942,15 +941,9 @@ dss_debugfs_create_file(struct dss_device *dss, const char *name,
>  
>  	entry->show_fn = show_fn;
>  	entry->data = data;
> +	entry->dentry = debugfs_create_file(name, 0444, dss->debugfs.root,
> +					    entry, &dss_debug_fops);
>  
> -	d = debugfs_create_file(name, 0444, dss->debugfs.root, entry,
> -				&dss_debug_fops);
> -	if (IS_ERR(d)) {
> -		kfree(entry);
> -		return ERR_CAST(d);
> -	}
> -
> -	entry->dentry = d;
>  	return entry;
>  }
>  

-- 
Regards,

Laurent Pinchart
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Re: [PATCH] omapdrm: no need to check return value of debugfs_create functions

[Tomi Valkeinen]

Hi,

On 08/08/2019 15:50, Laurent Pinchart wrote:
> Hi Greg,
> 
> Thank you for the patch.
> 
> On Thu, Jun 13, 2019 at 01:57:49PM +0200, Greg Kroah-Hartman wrote:
>> When calling debugfs functions, there is no need to ever check the
>> return value.  The function can work or not, but the code logic should
>> never do something different based on this.
>>
>> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
>> Cc: David Airlie <airlied@linux.ie>
>> Cc: Daniel Vetter <daniel@ffwll.ch>
>> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> Cc: Sebastian Reichel <sebastian.reichel@collabora.com>
>> Cc: Jyri Sarha <jsarha@ti.com>
>> Cc: Tony Lindgren <tony@atomide.com>
>> Cc: zhong jiang <zhongjiang@huawei.com>
>> Cc: dri-devel@lists.freedesktop.org
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> This makes sense.
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> Tomi, will you take this patch in your tree ?

Yes, I'll pick this up. I presume debugfs_create_file() will give a 
warning print if it fails to create the file, instead of being silent.

  Tomi

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Re: [PATCH] omapdrm: no need to check return value of debugfs_create functions

[Greg Kroah-Hartman]

On Fri, Aug 09, 2019 at 09:59:56AM +0300, Tomi Valkeinen wrote:
> Hi,
> 
> On 08/08/2019 15:50, Laurent Pinchart wrote:
> > Hi Greg,
> > 
> > Thank you for the patch.
> > 
> > On Thu, Jun 13, 2019 at 01:57:49PM +0200, Greg Kroah-Hartman wrote:
> > > When calling debugfs functions, there is no need to ever check the
> > > return value.  The function can work or not, but the code logic should
> > > never do something different based on this.
> > > 
> > > Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> > > Cc: David Airlie <airlied@linux.ie>
> > > Cc: Daniel Vetter <daniel@ffwll.ch>
> > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > Cc: Sebastian Reichel <sebastian.reichel@collabora.com>
> > > Cc: Jyri Sarha <jsarha@ti.com>
> > > Cc: Tony Lindgren <tony@atomide.com>
> > > Cc: zhong jiang <zhongjiang@huawei.com>
> > > Cc: dri-devel@lists.freedesktop.org
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > 
> > This makes sense.
> > 
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > 
> > Tomi, will you take this patch in your tree ?
> 
> Yes, I'll pick this up. I presume debugfs_create_file() will give a warning
> print if it fails to create the file, instead of being silent.

Yes it does, please see 43e23b6c0b01 ("debugfs: log errors when
something goes wrong") and c33d442328f5 ("debugfs: make error message a
bit more verbose") for the details if you are curious.

Those warnings have already found at least one user of debugfs that was
doing things wrong and no one had noticed before.

thanks,

greg k-h
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