From: Linus Walleij <linus.walleij@linaro.org>
To: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Alexandre Courbot <gnurou@gmail.com>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
Alexandre Belloni <alexandre.belloni@free-electrons.com>,
Nicolas Ferre <nicolas.ferre@atmel.com>,
Boris Brezillon <boris.brezillon@free-electrons.com>
Subject: Re: Requesting as a GPIO a pin already used through pinctrl
Date: Sun, 18 Sep 2016 13:30:24 +0200 [thread overview]
Message-ID: <CACRpkdbZ-TCNmmt4NyL2cQ2W3dE42uFGjQtxRyMxrf2ZUA_9Rg@mail.gmail.com> (raw)
In-Reply-To: <20160916135808.GA17518@lukather>
On Fri, Sep 16, 2016 at 3:58 PM, Maxime Ripard
<maxime.ripard@free-electrons.com> wrote:
> However, things are getting weird when you have that requested pin
> assigned to one device, and you try to export the GPIO on that pin
> (through sysfs for example,
DON'T use sysfs. Use the new chardev ABI which is by the way enabled
by default.
(But you will face the same issue there I guess.)
> but given the implementation, I think that
> it would work alike by calling gpiod_request).
Yes
> In this case, you get no error, and the GPIO is indeed exported,
> allowing the user to change the direction and / or value of the pin,
> taking away that pin from its device.
If and only if the pin controller does not specify .strict in
struct pinmux_ops.
> I have the feeling that the core should prevent that, making sure that
> the gpiod_request returns EBUSY in such a case, but I'm not really
> sure whether it's the case or not, and if it is, where that check is
> happening.
- Did you try specifying .strict for the pinmux?
- Did you read Documentation/pinctrl.txt, section titled
"GPIO mode pitfalls"?
Yours,
Linus Walleij
next prev parent reply other threads:[~2016-09-18 11:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-16 13:58 Requesting as a GPIO a pin already used through pinctrl Maxime Ripard
2016-09-18 11:30 ` Linus Walleij [this message]
2016-09-21 19:51 ` Maxime Ripard
2016-09-21 20:34 ` Michael Welling
2016-09-22 10:48 ` Maxime Ripard
2016-09-22 15:46 ` Michael Welling
2016-09-23 13:22 ` Linus Walleij
2016-09-23 15:24 ` Vladimir Zapolskiy
2016-09-23 21:34 ` Maxime Ripard
2016-09-30 16:26 ` Linus Walleij
2016-09-23 21:05 ` Maxime Ripard
2016-10-26 15:49 ` Maxime Ripard
2016-10-27 12:12 ` Linus Walleij
2016-11-02 21:31 ` Maxime Ripard
2016-11-06 10:11 ` Linus Walleij
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