linux-kernel - Re: [PATCH 1/2]drivers/usb/core/sysfs.c Fix variable 'retval' set but not used

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Date:	Tue, 03 Aug 2010 11:13:32 -0400
From:	Valdis.Kletnieks@...edu
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	"Justin P. Mattock" <justinmattock@...il.com>,
	linux-usb@...r.kernel.org, dbrownell@...rs.sourceforge.net,
	gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2]drivers/usb/core/sysfs.c Fix variable 'retval' set but not used

On Tue, 03 Aug 2010 10:29:52 EDT, Alan Stern said:
> On Tue, 3 Aug 2010 Valdis.Kletnieks@...edu wrote:
> 
> > On Mon, 02 Aug 2010 21:26:28 PDT, "Justin P. Mattock" said:
> > > diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
> > 
> > >  	if (alt->string)
> > > -		retval = device_create_file(&intf->dev, &dev_attr_interface);
> > > +		device_create_file(&intf->dev, &dev_attr_interface);
> > >  	intf->sysfs_files_created = 1;
> > >  	return 0;
> 
> Justin, did you try compiling your new code?  Those unused values are 
> there because device_create_file is declared as __must_check.
> 
> > What should the code do if device_create_file() manages to fail? Yes, ignoring
> > the return value is one option, but is it the best one?  'return ret;' might be
> > another one. Somebody who understands this code and has more caffeine than me
> > should look this over.
> 
> Failure to create a file in sysfs is almost never fatal and usually not 
> even dangerous.  Ignoring the error is generally better than failing 
> the entire operation.

Then why the __must_check attribute if it's usually ignorable? I thought
that was reserved for functions that you damned sight better well check
for errors because bad things are afoot otherwise?

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