From: Johan Hovold <johan@kernel.org>
To: Karoly Pados <pados@pados.hu>
Cc: Johan Hovold <johan@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
Loic Poulain <loic.poulain@linaro.org>
Subject: [v4] USB: serial: ftdi_sio: implement GPIO support for FT-X devices
Date: Tue, 18 Sep 2018 13:19:12 +0200 [thread overview]
Message-ID: <20180918111912.GE3943@localhost> (raw)
On Tue, Sep 18, 2018 at 10:27:58AM +0000, Karoly Pados wrote:
> >> Does that mean something can call into our module while this method is running?
> >> If not, I'm clueless about the possible race here.
> >
> > Correct, you can get gpio callbacks until the gpio chip has been
> > deregistered (anything coming in after that would be a gpiolib bug).
>
> I'm just puzzled by the fact that this can still happen even while the port
> removal code is running. It also makes me ask the question what else here can
> run in parallel. Don't we need mutexes here-and-there in the ftx gpio functions too
> in this case? Or does gpiolib make sure to serialize multiple pin and direction
> setting calls?
Good point. The old sysfs interface would keep things serialised, but
the new chardev-based one does not (nor does the in-kernel interface).
So yeah, we need to add a mutex protecting the gpio state (i.e.
direction and value).
Thanks,
Johan
next reply other threads:[~2018-09-18 11:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-18 11:19 Johan Hovold [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-09-18 10:27 [v4] USB: serial: ftdi_sio: implement GPIO support for FT-X devices Karoly Pados
2018-09-18 9:45 Johan Hovold
2018-09-18 9:35 Karoly Pados
2018-09-18 9:16 Johan Hovold
2018-09-16 17:58 Karoly Pados
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