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From: Johan Hovold <johan@kernel.org>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hovold <johan@kernel.org>, shuah <shuah@kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	"open list:NFC SUBSYSTEM" <linux-wireless@vger.kernel.org>,
	chris@the-brannons.com, devel@driverdev.osuosl.org,
	Rob Herring <robh@kernel.org>,
	Samuel Ortiz <sameo@linux.intel.com>,
	"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
	Jiri Slaby <jslaby@suse.com>,
	santhameena13@gmail.com, kirk@reisers.ca,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>,
	samuel.thibault@ens-lyon.org, m.maya.nakamura@gmail.com,
	zhongjiang@huawei.com, Greg KH <gregkh@linuxfoundation.org>,
	speakup@linux-speakup.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Bluez mailing list <linux-bluetooth@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>,
	nishka.dasgupta_ug18@ashoka.edu.in,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH] tty: Fix WARNING in tty_set_termios
Date: Thu, 31 Jan 2019 16:33:06 +0100	[thread overview]
Message-ID: <20190131153306.GT3691@localhost> (raw)
In-Reply-To: <D0EE5C33-2930-4286-998C-822DD7898B76@holtmann.org>

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.

Johan

WARNING: multiple messages have this Message-ID (diff)
From: Johan Hovold <johan@kernel.org>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hovold <johan@kernel.org>, shuah <shuah@kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	"open list:NFC SUBSYSTEM" <linux-wireless@vger.kernel.org>,
	chris@the-brannons.com, devel@driverdev.osuosl.org,
	Rob Herring <robh@kernel.org>,
	Samuel Ortiz <sameo@linux.intel.com>,
	"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
	Jiri Slaby <jslaby@suse.com>,
	santhameena13@gmail.com, kirk@reisers.ca,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>,
	samuel.thibault@ens-lyon.org, m.maya.nakamura@gmail.com,
	zhongjiang@huawei.com, Greg KH <gregkh@linuxfoundation.org>,
	speakup@linux-speakup.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Bluez mailing list <linux-bluetooth@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH] tty: Fix WARNING in tty_set_termios
Date: Thu, 31 Jan 2019 16:33:06 +0100	[thread overview]
Message-ID: <20190131153306.GT3691@localhost> (raw)
In-Reply-To: <D0EE5C33-2930-4286-998C-822DD7898B76@holtmann.org>

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.

Johan

  reply	other threads:[~2019-01-31 15:33 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-25 23:29 [PATCH] tty: Fix WARNING in tty_set_termios Shuah Khan
2019-01-26  4:14 ` Al Viro
2019-01-28 21:29   ` shuah
2019-01-30 10:32     ` Johan Hovold
2019-01-31  0:35       ` shuah
2019-01-31 15:18       ` Marcel Holtmann
2019-01-31 15:18         ` Marcel Holtmann
2019-01-31 15:33         ` Johan Hovold [this message]
2019-01-31 15:33           ` Johan Hovold
2019-01-31 23:23           ` shuah
2019-01-31 23:23             ` shuah

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