linux-kernel - Re: [PATCH 7/7] media: usb: uvc: no need to check return value of debugfs

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Date:   Thu, 17 Sep 2020 15:37:57 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-media@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] media: usb: uvc: no need to check return value of
 debugfs_create functions

Hi Greg,

On Thu, Sep 17, 2020 at 02:34:26PM +0200, Greg Kroah-Hartman wrote:
> On Thu, Sep 17, 2020 at 03:25:50PM +0300, Laurent Pinchart wrote:
> > On Wed, Aug 19, 2020 at 02:47:19AM +0300, Laurent Pinchart wrote:
> > > On Tue, Aug 18, 2020 at 03:36:08PM +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.
> > > 
> > > Is there no value in warning the user that something went wrong ? Silent
> > > failures are harder to debug.
> > 
> > Could yous share your opinion about this ?
> 
> For debugfs, this isn't an issue, what can a user do with something like
> "debugfs isn't working?  What does that mean???"
> 
> And if we _really_ want warnings like this, it should go into the
> debugfs core, not require this to be done for every debugfs user, right?
> 
> debugfs is just there for kernel developers to help debug things, it's
> not a dependancy on any userspace functionality, so if it works or not
> should not be an issue for any user.
> 
> Unless that user is a kernel developer of course :)

Exactly my point :-)

I'm fine moving the error message to the debugfs core itself instead of
duplicating it in drivers. Maybe it's already there though, I haven't
checked. Not printing any message isn't a great idea in my opinion, it
makes debugging more difficult. I can't count the number of times where
I've had to add printk's and recompile the kernel to debug issues that
really should have generated at least a dev_dbg().

-- 
Regards,

Laurent Pinchart