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gpiolib: Export gpiochip_request_own_desc and gpiochip_free_own_desc

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Both functions were introduced to let gpio drivers request their own
gpio pins. Without exporting the functions, this can however only be
used by gpio drivers built into the kernel.

Secondary impact is that the functions can not currently be used by
platform initialization code associated with the gpio-pca953x driver.
This code permits auto-export of gpio pins through platform data, but
if this functionality is used, the module can no longer be unloaded due
to the problem solved with the introduction of gpiochip_request_own_desc
and gpiochip_free_own_desc.

Export both function so they can be used from modules and from
platform initialization code.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Guenter Roeck 2014-07-22 08:01:01 -07:00 committed by Linus Walleij
parent d82da79722
commit f7d4ad98fd
4 changed files with 26 additions and 3 deletions
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21
Documentation/gpio/driver.txt
View File

@ -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.

2
drivers/gpio/gpiolib.c
View File

@ -897,6 +897,7 @@ int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label)
return __gpiod_request(desc, label);
}
EXPORT_SYMBOL_GPL(gpiochip_request_own_desc);
/**
* gpiochip_free_own_desc - Free GPIO requested by the chip driver
@ -910,6 +911,7 @@ void gpiochip_free_own_desc(struct gpio_desc *desc)
if (desc)
__gpiod_free(desc);
}
EXPORT_SYMBOL_GPL(gpiochip_free_own_desc);
/* Drivers MUST set GPIO direction before making get/set calls. In
* some cases this is done in early boot, before IRQs are enabled.

3
drivers/gpio/gpiolib.h
View File

@ -45,9 +45,6 @@ acpi_get_gpiod_by_index(struct device *dev, int index,
}
#endif
int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label);
void gpiochip_free_own_desc(struct gpio_desc *desc);
struct gpio_desc *of_get_named_gpiod_flags(struct device_node *np,
const char *list_name, int index, enum of_gpio_flags *flags);

3
include/linux/gpio/driver.h
View File

@ -220,6 +220,9 @@ int gpiochip_irqchip_add(struct gpio_chip *gpiochip,
#endif /* CONFIG_GPIO_IRQCHIP */
int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label);
void gpiochip_free_own_desc(struct gpio_desc *desc);
#else /* CONFIG_GPIOLIB */
static inline struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)