[02/22] USB: typec: fsusb302: no need to check return value of debugfs_create_dir()

[Guenter Roeck <linux@roeck-us.net>]

On Tue, May 29, 2018 at 06:27:03PM +0200, Greg Kroah-Hartman wrote:
> On Tue, May 29, 2018 at 09:15:30AM -0700, Guenter Roeck wrote:
> > On Tue, May 29, 2018 at 05:30:47PM +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.
> > > 
> > > Clean up the fsusb302 driver to not care about the dentry being created,
> > > or if the root directory was created, as the code should work properly
> > > either way.  We do not need to save the dentry anymore as things are
> > > properly cleaned up when we remove the root directory.
> > > 
> > > Note, this driver seems to only work for one device per system,
> > > otherwise the debugfs directories are going to get confused when a
> > > device is removed.
> > > 
> > > Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > > Cc: Guenter Roeck <linux@roeck-us.net>
> > > Cc: Hans de Goede <hdegoede@redhat.com>
> > > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > > Cc: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > ---
> > >  drivers/usb/typec/fusb302/fusb302.c | 24 +++++++-----------------
> > >  1 file changed, 7 insertions(+), 17 deletions(-)
> > > 
> > > diff --git a/drivers/usb/typec/fusb302/fusb302.c b/drivers/usb/typec/fusb302/fusb302.c
> > > index 9c1eba9ea004..07b07ddf6af0 100644
> > > --- a/drivers/usb/typec/fusb302/fusb302.c
> > > +++ b/drivers/usb/typec/fusb302/fusb302.c
> > > @@ -117,7 +117,6 @@ struct fusb302_chip {
> > >  	u32 snk_pdo[PDO_MAX_OBJECTS];
> > >  
> > >  #ifdef CONFIG_DEBUG_FS
> > > -	struct dentry *dentry;
> > >  	/* lock for log buffer access */
> > >  	struct mutex logbuffer_lock;
> > >  	int logbuffer_head;
> > > @@ -215,33 +214,26 @@ DEFINE_SHOW_ATTRIBUTE(fusb302_debug);
> > >  
> > >  static struct dentry *rootdir;
> > >  
> > > -static int fusb302_debugfs_init(struct fusb302_chip *chip)
> > > +static void fusb302_debugfs_init(struct fusb302_chip *chip)
> > >  {
> > >  	mutex_init(&chip->logbuffer_lock);
> > > -	if (!rootdir) {
> > > +	if (!rootdir)
> > >  		rootdir = debugfs_create_dir("fusb302", NULL);
> > > -		if (!rootdir)
> > > -			return -ENOMEM;
> > > -	}
> > > -
> > > -	chip->dentry = debugfs_create_file(dev_name(chip->dev),
> > > -					   S_IFREG | 0444, rootdir,
> > > -					   chip, &fusb302_debug_fops);
> > >  
> > > -	return 0;
> > > +	debugfs_create_file(dev_name(chip->dev), S_IFREG | 0444, rootdir, chip,
> > > +			    &fusb302_debug_fops);
> > >  }
> > >  
> > >  static void fusb302_debugfs_exit(struct fusb302_chip *chip)
> > >  {
> > > -	debugfs_remove(chip->dentry);
> > > -	debugfs_remove(rootdir);
> > > +	debugfs_remove_recursive(rootdir);
> > 
> > The idea was that debugfs_remove() would only remove the root directory
> > if nothing else was in it. This was the reason for the preceding
> > debugfs_remove(chip->dentry) followed by debugfs_remove(). Your patch
> > changes this behavior. "... this driver seems to only work for one
> > device per system" is introduced by your patch and was not previously
> > the case.
> 
> Ah, that makes more sense.  Nice hack :)
> 
> Why not just have a new directory per device like "most" drivers have?
> That would make this a bit simpler to manage.  Mind of I change the code
> that way?  Hm, you still end up having to save off a dentry that way,
> ah, it's the same either way...
> 

I personally prefer some kind of grouping, such as done for regulators.
Of course, that is easier if there is a subsystem behind it. No strong
opinion either way. And, yes, you'll still need to store dentry somewhere
to be able to remove it.

Guenter
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