linux-kernel - Re: [PATCH v2 1/2] USB: serial: ark3116: Remove unused TIOCSSERIAL ioctl case.

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Date:   Tue, 9 Jan 2018 12:55:35 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Mikhail Zaytsev <flashed@...l.ru>
Cc:     Johan Hovold <johan@...nel.org>, Oliver Neukum <oneukum@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 1/2] USB: serial: ark3116: Remove unused TIOCSSERIAL
 ioctl case.

On Tue, Jan 09, 2018 at 12:45:30AM +0300, Mikhail Zaytsev wrote:
> On Mon, 8 Jan 2018 16:28:58 +0100 Johan Hovold <johan@...nel.org> wrote:
> 
> > On Mon, Jan 08, 2018 at 11:33:32AM +0100, Oliver Neukum wrote:
> > > Am Samstag, den 06.01.2018, 20:14 +0300 schrieb Mikhail Zaytsev:  
> > > > The patch removes unused TIOCSSERIAL ioctl case and adds the default block
> > > > to the switch. This will make the ioctl return -ENOTTY to user space (e.g.
> > > > setserial), because TIOCSSERIAL really isn't supported for these devices
> > > > currently.  
> > > 
> > > Hi,
> > > 
> > > this will break software that is now running on these devices,
> > > won't it? Do you know why those devices basically ignore the
> > > ioctl?  
> > 
> > Yeah, that was my initial reactions as well, but then again, any sane
> > user space cannot rely on these ioctl being implemented for all tty
> > devices.
> > 
> > I did some digging now and these (dummy) ioctl implementations where
> > added by commit 2f430b4bbae7 ("USB: ark3116: Add TIOCGSERIAL and
> > TIOCSSERIAL ioctl calls.") back in 2006.  This in turn appears to have
> > been triggered by a change in a user space tool, wvdial, which started
> > erroring out if either was missing.
> > 
> > I found a couple of bug reports about that through google, and looking
> > at the wvstreams (library) code now, it looks like the issue has indeed
> > been resolved by handling errors more gracefully (e.g. just logging
> > them).
> > 
> > So I'm willing to give this a try, and if anyone complains later we add
> > back (or implement) TIOCSSERIAL.
> > 
> 
> Thanks Johan. I looked the commit 2f430b4bbae7. Author just did a cut'n'paste
>  from other USB serial drivers. I think that it would be better remove
> the TIOCGSERIAL implementation too.

I've applied this one now after adding some of the backstory from above
to the commit message.

Thanks,
Johan