Re: [PATCH] tty: Fix WARNING in tty_set_termios

[shuah]

On 1/31/19 8:33 AM, Johan Hovold wrote:
> On Thu, Jan 31, 2019 at 04:18:33PM +0100, Marcel Holtmann wrote:
>
> > > I agree with Al that this change doesn't make much sense. The WARN_ON
> > > is there to catch any bugs leading to the termios being changed for a
> > > master side pty. Those should bugs should be fixed, and not worked
> > > around in order to silence a WARN_ON.
> > >
> > > The problem started with 7721383f4199 ("Bluetooth: hci_uart: Support
> > > operational speed during setup") which introduced a new way for how
> > > tty_set_termios() could end up being called for a master pty.
> > >
> > > As Al hinted at, setting these ldiscs for a master pty really makes no
> > > sense and perhaps that is what we should prevent unless simply making
> > > sure they do not call tty_set_termios() is sufficient for the time
> > > being.
> > >
> > > Finally, note that serdev never operates on a pty, and that this is only
> > > an issue for (the three) line disciplines.
> >
> > I think for PTYs we should just fail setting the HCI line discipline.
> > Fail early and just move on with life.
>
> Sounds good to me. At least for the pty master. There may be some people
> trying to use a bluetooth device connected to a remote serial port (I've
> seen descriptions of such setups at least), and maybe we need not prevent
> that.

Thanks for the feedback on the patch. Changes to prevent setting the HCI
line discipline from hci_uart fixes the problem.

I am sending v2 in a just a bit.

thanks,
-- Shuah