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-rw-r--r--Documentation/gpio.txt35
-rw-r--r--drivers/gpio/gpiolib.c12
2 files changed, 35 insertions, 12 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index c2c6e9b..d96a6db 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -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
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6a6bd56..1a8c18c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -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);
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