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Date:   Fri, 15 Nov 2019 11:19:51 +0800
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     USB list <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Jonathan Corbet <corbet@lwn.net>,
        Felipe Balbi <balbi@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>
Subject: Re: [PATCH 1/1] usb: gadget: add raw-gadget interface
Message-ID: <20191115031951.GA793701@kroah.com>
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 <20191108211745.GA1282512@kroah.com>
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On Thu, Nov 14, 2019 at 04:08:29PM +0100, Andrey Konovalov wrote:
> On Fri, Nov 8, 2019 at 10:17 PM Greg Kroah-Hartman
> > > +static void gadget_unbind(struct usb_gadget *gadget)
> > > +{
> > > +     struct raw_dev *dev = get_gadget_data(gadget);
> > > +     unsigned long flags;
> > > +
> > > +     if (WARN_ON(!dev))
> > > +             return;
> >
> > Why warn?  How can this happen?
> 
> This shouldn't happen and I initially had BUG_ON there, but checkpatch
> complained. I can use BUG_ON of leave it as WARN_ON, which would you
> prefer?

If it should never happen, then why test it?
If it can happen, then just test and print an error, why panic the
machine if panic-on-warn is enabled for something that we can test and
recover from?

And no, never add BUG_ON please.

> > > +static int raw_open(struct inode *inode, struct file *fd)
> > > +{
> > > +     struct raw_dev *dev;
> > > +
> > > +     dev = dev_new();
> > > +     if (!dev) {
> > > +             pr_err("failed to created device");
> >
> > So many error messages printed on failures, you only needed the original
> > one if memory was gone that the core sent out.
> 
> What do you mean by the original one? I see only one error printed in
> case dev_new() fails. However I'm not sure if there's much value in
> printing an error in case the kernel ran out of memory, as it doesn't
> handle this very well anyway AFAIK. Should I remove this pr_err?

Yes, please do.

thanks,

greg k-h