linux.git/Documentation/gpio.txt, branch master

Documentation: gpiolib: document new interface

2013-11-25T08:02:30+00:00

gpiolib now exports a new descriptor-based interface which deprecates
the older integer-based one. This patch documents this new interface and
also takes the opportunity to brush-up the GPIO documentation a little
bit.

The new descriptor-based interface follows the same consumer/driver
model as many other kernel subsystems (e.g. clock, regulator), so its
documentation has similarly been splitted into different files.

The content of the former documentation has been reused whenever it
made sense; however, some of its content did not apply to the new
interface anymore and have this been removed. Likewise, new sections
like the mapping of GPIOs to devices have been written from scratch.

The deprecated legacy-based documentation is still available, untouched,
under Documentation/gpio/gpio-legacy.txt.

Signed-off-by: Alexandre Courbot 
Signed-off-by: Linus Walleij

Remove GENERIC_GPIO config option

2013-04-16T09:47:19+00:00

GENERIC_GPIO has been made equivalent to GPIOLIB in architecture code
and all driver code has been switch to depend on GPIOLIB. It is thus
safe to have GENERIC_GPIO removed.

Signed-off-by: Alexandre Courbot 
Acked-by: Linus Walleij 
Acked-by: Grant Likely

gpiolib: provide provision to register pin ranges

2012-11-11T18:06:00+00:00

pinctrl subsystem needs gpio chip base to prepare set of gpio
pin ranges, which a given pinctrl driver can handle. This is
important to handle pinctrl gpio request calls in order to
program a given pin properly for gpio operation.

As gpio base is allocated dynamically during gpiochip
registration, presently there exists no clean way to pass this
information to the pinctrl subsystem.

After few discussions from [1], it was concluded that may be
gpio controller reporting the pin range it supports, is a
better way than pinctrl subsystem directly registering it.

[1] http://comments.gmane.org/gmane.linux.ports.arm.kernel/184816

Cc: Grant Likely 
Signed-off-by: Viresh Kumar 
Signed-off-by: Shiraz Hashim 
[Edited documentation a bit]
Signed-off-by: Linus Walleij

gpio: add flags to export GPIOs when requesting

2012-04-06T04:24:06+00:00

Introduce new flags to automatically export GPIOs when using the convenience
functions gpio_request_one() or gpio_request_array(). This eases support for
custom boards where lots of GPIOs need to be exported for customer
applications.

Signed-off-by: Wolfram Sang 
Signed-off-by: Grant Likely

Documentation/gpio.txt: Explain expected pinctrl interaction

2012-03-12T17:27:07+00:00

Update gpio.txt based on recent discussions regarding interaction with the
pinctrl subsystem.

Previously, gpio_request() was described as explicitly not performing any
required mux setup operations etc.

Now, gpio_request() is explicitly as explicitly performing any required mux
setup operations where possible. In the case it isn't, platform code is
required to have set up any required muxing or other configuration prior to
gpio_request() being called, in order to maintain the same semantics.

This is achieved by gpiolib drivers calling e.g. pinctrl_request_gpio() in
their .request() operation.

Cc: Randy Dunlap 
Cc: linux-doc@vger.kernel.org
Signed-off-by: Stephen Warren 
Reviewed-by: Linus Walleij 
Signed-off-by: Grant Likely

Documentation: gpio: Add details of open-drain/source configuration

2012-03-05T14:49:44+00:00

Adding details of open drain(open collector) and open source
(open emitter) configuration of the gpio so that client can
set the pin as open drain at the time of gpio request.

Signed-off-by: Laxman Dewangan 
Reviwed-by: Mark Brown 
Acked-by: Linus Walleij 
Signed-off-by: Grant Likely

Revert "gpiolib: annotate gpio-intialization with __must_check"

2011-01-14T01:26:46+00:00

This reverts commit 0fdae42d361bbb431ca0ab0efed5126a94821177, which
wasn't really supposed to go in, and causes lots of annoying warnings.

Quoth Andrew:
  "Complete brainfart - I meant to drop that patch ages ago."

Quoth Greg:
  "Ick, yeah, that patch isn't ok to go in as-is, all of the callers
   need to be fixed up first, which is what I thought we had agreed on..."

Reported-by: Stephen Rothwell 
Acked-by: Andrew Morton 
Acked-by: Greg KH 
Signed-off-by: Linus Torvalds

gpiolib: annotate gpio-intialization with __must_check

2011-01-13T16:03:14+00:00

Because GPIOs can have crucial functions especially in embedded systems,
we are better safe than sorry regarding their configuration.  For
gpio_request, the documentation is simply enforced: "The return
value of gpio_request() must be checked." For gpio_direction_* and
gpio_request_*, we now act accordingly.

Signed-off-by: Wolfram Sang 
Cc: David Brownell 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation/gpio.txt: explain poll/select usage

2010-11-18T23:00:46+00:00

Add a bit more information how to use poll(2) on GPIO value files
correctly. For me it was not clear that I need to poll(2) for
POLLPRI|POLLERR or select(2) for exceptfds.

Signed-off-by: Bernhard Walle 
Signed-off-by: Randy Dunlap 
Signed-off-by: Linus Torvalds

gpio: doc updates

2010-09-10T01:57:24+00:00

There's been some recent confusion about error checking GPIO numbers.
briefly, it should be handled mostly during setup, when gpio_request() is
called, and NEVER by expectig gpio_is_valid to report more than
never-usable GPIO numbers.

[akpm@linux-foundation.org: terminate unterminated comment]
Signed-off-by: David Brownell 
Cc: Eric Miao" 
Cc: "Ryan Mallon" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds