linux-kernel - Re: [PATCH 0/2] usb: serial: handle -ENODEV and -EPROTO quietly

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Date:	Mon, 15 Dec 2014 08:38:01 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Jeremiah Mahler <jmmahler@...il.com>,
	Johan Hovold <johan@...nel.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] usb: serial: handle -ENODEV and -EPROTO quietly

On Mon, Dec 15, 2014 at 04:53:05AM -0800, Jeremiah Mahler wrote:
> Johan,
> 
> On Mon, Dec 15, 2014 at 11:23:21AM +0100, Johan Hovold wrote:
> > On Thu, Dec 11, 2014 at 03:29:52PM -0800, Jeremiah Mahler wrote:
> > > If a USB serial device (e.g. /dev/ttyUSB0) with an active program is
> > > unplugged, a bunch of -ENODEV and -EPROTO errors will be produced in the
> > > logs.  This patch set quiets these messages without changing the
> > > original behavior.
> > 
> > Don't unplug devices that are in use then. ;)
> > 
> I knew someone was going to say that :-)
> 
> > > This change is beneficial when using daemons such as slcand, which is
> > > similar to pppd or slip, that cannot determine whether they should exit
> > > until after the USB serial device is unplugged.  Producing these error
> > > messages for a normal use case is not helpful.
> > 
> > Your patches would hide these errors when they occur during normal use
> > (e.g. EPROTO).
> > 
> > Receiving an error message when unplugging an active device should not
> > surprise anyone. And at least you know where it came from (and it's
> > right there in the logs as well).
> > 
> > Johan
> 
> Hmm.  Yes, I can see why quieting -EPROTO would be bad because it would
> hide protocol errors which we want to know about.

Do you really want to "know about" them?  What can a user do with them?
Nothing, so just resubmit and you should be fine.

> I need to re-think this patch.
> Nack.

I like this patch, putting crud in the kernel log that no one can do
anything with for a "normal" operation like yanking a USB device out
while it is open should not happen.

thanks,

greg k-h
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