diff options
Diffstat (limited to 'Documentation/gpio/driver.txt')
| -rw-r--r-- | Documentation/gpio/driver.txt | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt index fa9a0a8b3734..18790c237977 100644 --- a/Documentation/gpio/driver.txt +++ b/Documentation/gpio/driver.txt @@ -157,13 +157,34 @@ Locking IRQ usage Input GPIOs can be used as IRQ signals. When this happens, a driver is requested to mark the GPIO as being used as an IRQ: - int gpiod_lock_as_irq(struct gpio_desc *desc) + int gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset) This will prevent the use of non-irq related GPIO APIs until the GPIO IRQ lock is released: - void gpiod_unlock_as_irq(struct gpio_desc *desc) + void gpio_unlock_as_irq(struct gpio_chip *chip, unsigned int offset) When implementing an irqchip inside a GPIO driver, these two functions should typically be called in the .startup() and .shutdown() callbacks from the irqchip. + + +Requesting self-owned GPIO pins +------------------------------- + +Sometimes it is useful to allow a GPIO chip driver to request its own GPIO +descriptors through the gpiolib API. Using gpio_request() for this purpose +does not help since it pins the module to the kernel forever (it calls +try_module_get()). A GPIO driver can use the following functions instead +to request and free descriptors without being pinned to the kernel forever. + + int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label) + + void gpiochip_free_own_desc(struct gpio_desc *desc) + +Descriptors requested with gpiochip_request_own_desc() must be released with +gpiochip_free_own_desc(). + +These functions must be used with care since they do not affect module use +count. Do not use the functions to request gpio descriptors not owned by the +calling driver. |