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gpiolib: decouple might_sleep_if() from DEBUG 

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 <dbrownell@users.sourceforge.net>
Cc: Jani Nikula <ext-jani.1.nikula@nokia.com>
Cc: "Ryan Mallon" <ryan@bluewatersys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Brownell 2010-08-10 18:02:24 -07:00 committed by Linus Torvalds
parent 49946f6814
commit 9c4ba94661
2 changed files with 35 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
Documentation/gpio.txt
View File

@ -158,10 +158,11 @@ and configure pullups/pulldowns appropriately.)
Spinlock-Safe GPIO access
-------------------------
Most GPIO controllers can be accessed with memory read/write instructions.
That doesn't need to sleep, and can safely be done from inside IRQ handlers.
(That includes hardirq contexts on RT kernels.)
Those don't need to sleep, and can safely be done from inside hard
(nonthreaded) IRQ handlers and similar contexts.
Use these calls to access such GPIOs:
Use the following calls to access such GPIOs,
for which gpio_cansleep() will always return false (see below):
/* GPIO INPUT: return zero or nonzero */
int gpio_get_value(unsigned gpio);
@ -210,9 +211,31 @@ To access such GPIOs, a different set of accessors is defined:
/* GPIO OUTPUT, might sleep */
void gpio_set_value_cansleep(unsigned gpio, int value);
Other than the fact that these calls might sleep, and will not be ignored
for GPIOs that can't be accessed from IRQ handlers, these calls act the
same as the spinlock-safe calls.
Accessing such GPIOs requires a context which may sleep, for example
a threaded IRQ handler, and those accessors must be used instead of
spinlock-safe accessors without the cansleep() name suffix.
Other than the fact that these accessors might sleep, and will work
on GPIOs that can't be accessed from hardIRQ handlers, these calls act
the same as the spinlock-safe calls.
** IN ADDITION ** calls to setup and configure such GPIOs must be made
from contexts which may sleep, since they may need to access the GPIO
controller chip too: (These setup calls are usually made from board
setup or driver probe/teardown code, so this is an easy constraint.)
gpio_direction_input()
gpio_direction_output()
gpio_request()
## gpio_request_one()
## gpio_request_array()
## gpio_free_array()
gpio_free()
gpio_set_debounce()
Claiming and Releasing GPIOs

12
drivers/gpio/gpiolib.c
View File

@ -1272,7 +1272,7 @@ void gpio_free(unsigned gpio)
if (chip && test_bit(FLAG_REQUESTED, &desc->flags)) {
if (chip->free) {
spin_unlock_irqrestore(&gpio_lock, flags);
might_sleep_if(extra_checks && chip->can_sleep);
might_sleep_if(chip->can_sleep);
chip->free(chip, gpio - chip->base);
spin_lock_irqsave(&gpio_lock, flags);
}
@ -1410,7 +1410,7 @@ int gpio_direction_input(unsigned gpio)
spin_unlock_irqrestore(&gpio_lock, flags);
might_sleep_if(extra_checks && chip->can_sleep);
might_sleep_if(chip->can_sleep);
if (status) {
status = chip->request(chip, gpio);
@ -1463,7 +1463,7 @@ int gpio_direction_output(unsigned gpio, int value)
spin_unlock_irqrestore(&gpio_lock, flags);
might_sleep_if(extra_checks && chip->can_sleep);
might_sleep_if(chip->can_sleep);
if (status) {
status = chip->request(chip, gpio);
@ -1521,7 +1521,7 @@ int gpio_set_debounce(unsigned gpio, unsigned debounce)
spin_unlock_irqrestore(&gpio_lock, flags);
might_sleep_if(extra_checks && chip->can_sleep);
might_sleep_if(chip->can_sleep);
return chip->set_debounce(chip, gpio, debounce);
@ -1571,7 +1571,7 @@ int __gpio_get_value(unsigned gpio)
struct gpio_chip *chip;
chip = gpio_to_chip(gpio);
WARN_ON(extra_checks && chip->can_sleep);
WARN_ON(chip->can_sleep);
return chip->get ? chip->get(chip, gpio - chip->base) : 0;
}
EXPORT_SYMBOL_GPL(__gpio_get_value);
@ -1590,7 +1590,7 @@ void __gpio_set_value(unsigned gpio, int value)
struct gpio_chip *chip;
chip = gpio_to_chip(gpio);
WARN_ON(extra_checks && chip->can_sleep);
WARN_ON(chip->can_sleep);
chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(__gpio_set_value);