linux-toradex.git/Documentation/gpio.txt, branch v3.0.71

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

gpiolib: decouple might_sleep_if() from DEBUG

2010-08-11T15:59:08+00:00

Be more consistent about runtime programming interface abuse warnings,
which can reduce some confusion and trigger bugfixes.  Based on an
observation and patch from Jani Nikula.

Also update doc to highlight some sleeping-call issues and to match some
recent changes.

Signed-off-by: David Brownell 
Cc: Jani Nikula 
Cc: "Ryan Mallon" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpio: introduce gpio_request_one() and friends

2010-03-06T19:26:48+00:00

gpio_request() without initial configuration of the GPIO is normally
useless, introduce gpio_request_one() together with GPIOF_ flags for
input/output direction and initial output level.

gpio_{request,free}_array() for multiple GPIOs.

Signed-off-by: Eric Miao 
Cc: David Brownell 
Cc: Ben Nizette 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpiolib: add support for changing value polarity in sysfs

2009-12-16T15:20:01+00:00

Drivers may use gpiolib sysfs as part of their public user space
interface. The GPIO number and polarity might change from board to
board. The gpio_export_link() call can be used to hide the GPIO number
from user space. Add support for also hiding the GPIO line polarity
changes from user space.

Signed-off-by: Jani Nikula 
Cc: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

correct gpio.txt typos

2009-12-10T02:59:52+00:00

Corrected sysfs gpio chip node name and fixed punctuation.

Signed-off-by: Dominik D. Geyer 
Signed-off-by: Randy Dunlap 
Cc: David Brownell 
Signed-off-by: Linus Torvalds

gpiolib: allow poll() on value

2009-09-23T14:39:48+00:00

Many gpio chips allow to generate interrupts when the value of a pin
changes.  This patch gives usermode application the opportunity to make
use of this feature by calling poll(2) on the /sys/class/gpio/gpioN/value
sysfs file.  The edge to trigger can be set in the edge file in the same
directory.  Possible values are "none", "rising", "falling", and "both".

Using level triggers is not possible with current sysfs since nothing
changes the GPIO value (and the IRQ keeps triggering).  Edge triggering
will "just work".  Note that if there was an event between read() and
poll(), the poll() returns immediately.

Also note that this version only supports true GPIO interrupts.  Some
later patch might be able to synthesize this behavior by timer-driven
polling; some systems seem to need that.

[dbrownell@users.sourceforge.net: align ids to 16 bit ids; whitespace]
Signed-off-by: Daniel Glöckner 
Signed-off-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpiolib: allow exported GPIO nodes to be named using sysfs links

2009-09-23T14:39:46+00:00

Commit 926b663ce8215ba448960e1ff6e58b67a2c3b99b (gpiolib: allow GPIOs to
be named) already provides naming on the chip level. This patch provides
more flexibility by allowing multiple names where ever in sysfs on a per
GPIO basis.

Adapted from David Brownell's comments on a similar concept:
http://lkml.org/lkml/2009/4/20/203.

[randy.dunlap@oracle.com: fix build for CONFIG_GENERIC_GPIO=n]
Signed-off-by: Jani Nikula 
Acked-by: David Brownell 
Cc: Daniel Silverstone 
Signed-off-by: Randy Dunlap 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds