From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Eric Miao <eric.y.miao@gmail.com>
Cc: Peter Tyser <ptyser@xes-inc.com>,
linux-kernel@vger.kernel.org, Alek Du <alek.du@intel.com>,
Samuel Ortiz <sameo@linux.intel.com>,
David Brownell <dbrownell@users.sourceforge.net>,
Mark Brown <broonie@opensource.wolfsonmicro.com>,
Joe Perches <joe@perches.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Grant Likely <grant.likely@secretlab.ca>
Subject: Re: [PATCH v2 1/4] gpiolib: Add "unknown" direction support
Date: Thu, 17 Feb 2011 12:05:47 +0100 [thread overview]
Message-ID: <20110217110547.GN22310@pengutronix.de> (raw)
In-Reply-To: <AANLkTi=yZZgh0v+-_Cw0JudAxxTZuBWeVCEZ-dBtENPw@mail.gmail.com>
On Thu, Feb 17, 2011 at 03:33:42PM +0800, Eric Miao wrote:
> On Thu, Feb 17, 2011 at 8:56 AM, Peter Tyser <ptyser@xes-inc.com> wrote:
> > Previously, gpiolib would unconditionally flag all GPIO pins as inputs,
> > regardless of their true state. This resulted in all GPIO output pins
> > initially being incorrectly identified as "input" in the GPIO sysfs.
> >
> > Since the direction of GPIOs is not known prior to having their
> > direction set, instead set the default direction to "unknown" to prevent
> > user confusion. A pin with an "unknown" direction can not be written or
> > read via sysfs; it must first be configured as an input or output before
> > it can be used.
> >
>
> Hrm... that's why I don't like the original definition of gpio_request()
> which is vague on the pin configurations. The pin configuration should
> be clear upon requesting, otherwise it's a potential issue.
I don't know (state: "unknown" :-) what you would prefer here. An
implicit gpio_direction_input()? Or gpio_reserve_and_direction_input()?
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
next prev parent reply other threads:[~2011-02-17 11:05 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-17 0:56 [PATCH v2 1/4] gpiolib: Add "unknown" direction support Peter Tyser
2011-02-17 0:56 ` [PATCH v2 2/4] gpiolib: Add ability to get GPIO pin direction Peter Tyser
2011-02-17 11:00 ` Wolfram Sang
2011-02-17 0:56 ` [PATCH v2 3/4] gpio: pca953x: Implement get_direction() hook Peter Tyser
2011-02-17 0:56 ` [PATCH v2 4/4] gpio: Add support for Intel ICHx/3100/Series[56] GPIO Peter Tyser
2011-02-17 7:33 ` [PATCH v2 1/4] gpiolib: Add "unknown" direction support Eric Miao
2011-02-17 11:05 ` Uwe Kleine-König [this message]
2011-02-17 12:03 ` Lars-Peter Clausen
2011-02-17 12:21 ` Alexander Stein
2011-02-17 13:06 ` Lars-Peter Clausen
2011-02-21 9:09 ` Alexander Stein
2011-02-21 9:19 ` Wolfram Sang
2011-02-21 9:37 ` Alexander Stein
2011-02-21 9:47 ` Wolfram Sang
2011-02-21 11:07 ` Alexander Stein
2011-02-21 11:22 ` Wolfram Sang
2011-02-21 11:38 ` Alexander Stein
2011-02-21 20:25 ` Ryan Mallon
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