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Diffstat (limited to 'Documentation/gpio/driver.txt')
| -rw-r--r-- | Documentation/gpio/driver.txt | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt index 224dbbcd1804..18790c237977 100644 --- a/Documentation/gpio/driver.txt +++ b/Documentation/gpio/driver.txt @@ -167,3 +167,24 @@ is released: 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. |