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path: root/Documentation/gpio.txt
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2008-03-04gpio: <linux/gpio.h> and "no GPIO support here" stubsDavid Brownell
Add a <linux/gpio.h> defining fail/warn stubs for GPIO calls on platforms that don't support the GPIO programming interface. That includes the arch-specific implementation glue otherwise. This facilitates a new model for GPIO usage: drivers that can use GPIOs if they're available, but don't require them. One example of such a driver is NAND driver for various FreeScale chips. On platforms update with GPIO support, they can be used instead of a worst-case delay to verify that the BUSY signal is off. (Also includes a couple minor unrelated doc updates.) Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05gpiolib: update Documentation/gpio.txtDavid Brownell
Update Documentation/gpio.txt, primarily to include the new "gpiolib" infrastructure. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Jean Delvare <khali@linux-fr.org> Cc: Eric Miao <eric.miao@marvell.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Haavard Skinnemoen <hskinnemoen@atmel.com> Cc: Philipp Zabel <philipp.zabel@gmail.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ben Gardner <bgardner@wabtec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-24minor gpio doc updateDavid Brownell
Fix doc bug noted by Uwe Kleine-König: gpio_set_direction() is long gone, replaced by gpio_direction_input() and gpio_direction_output(). Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: <ukleinek@informatik.uni-freiburg.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-19gpio calls don't need i/o barriersDavid Brownell
Clarify that drivers using the GPIO operations don't need to issue io barrier instructions themselves. Previously this wasn't clear, and at least one platform assumed otherwise (and would thus break various otherwise-portable drivers which don't issue barriers). Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-17gpio interface loosens call restrictionsDavid Brownell
Loosen gpio_{request,free}() and gpio_direction_{in,out}put() call context restrictions slightly, so a common idiom is no longer an error: board init code setting up spinlock-safe GPIOs before tasking is enabled. The issue was caught by some paranoid code with might_sleep() checks. The legacy platform-specific GPIO interfaces stick to spinlock-safe GPIOs, so this change reflects current implementations and won't break anything. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-11Documentation/gpio.txt mentions GENERIC_GPIODavid Brownell
Documentation/gpio.txt should mention the Kconfig GENERIC_GPIO flag, for platforms to declare when relevant. This should help minimize goofs like omitting it, or not depending on it when needed. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-04-12[PATCH] doc: gpio.txt describes open-drain emulationDavid Brownell
Update the GPIO docs to describe the idiom whereby open drain signals are emulated by toggling the GPIO direction. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-03-16[PATCH] gpio_direction_output() needs an initial valueDavid Brownell
It's been pointed out that output GPIOs should have an initial value, to avoid signal glitching ... among other things, it can be some time before a driver is ready. This patch corrects that oversight, fixing - documentation - platforms supporting the GPIO interface - users of that call (just one for now, others are pending) There's only one user of this call for now since most platforms are still using non-generic GPIO setup code, which in most cases already couples the initial value with its "set output mode" request. Note that most platforms are clear about the hardware letting the output value be set before the pin direction is changed, but the s3c241x docs are vague on that topic ... so those chips might not avoid the glitches. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Andrew Victor <andrew@sanpeople.com> Acked-by: Milan Svoboda <msvoboda@ra.rockwell.com> Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16[PATCH] GPIO core documentationDavid Brownell
Small updates to the GPIO documentation, addressing feedback and fixing a few spelling errors. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-12[PATCH] GPIO coreDavid Brownell
This defines a simple and minimalist programming interface for GPIO APIs: - Documentation/gpio.txt ... describes things (read it) - include/asm-arm/gpio.h ... defines the ARM hook, which just punts to <asm/arch/gpio.h> for any implementation - include/asm-generic/gpio.h ... implement "can sleep" variants as calling the normal ones, for systems that don't handle i2c expanders. The immediate need for such a cross-architecture API convention is to support drivers that work the same on AT91 ARM and AVR32 AP7000 chips, which embed many of the same controllers but have different CPUs. However, several other users have been reported, including a driver for a hardware watchdog chip and some handhelds.org multi-CPU button drivers. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>