gpio: Introduce ->get_multiple callback
SPI-attached GPIO controllers typically read out all inputs in one go.
If callers desire the values of multipe inputs, ideally a single readout
should take place to return the desired values. However the current
driver API only offers a ->get callback but no ->get_multiple (unlike
->set_multiple, which is present). Thus, to read multiple inputs, a
full readout needs to be performed for every single value (barring
driver-internal caching), which is inefficient.
In fact, the lack of a ->get_multiple callback has been bemoaned
repeatedly by the gpio subsystem maintainer:
http://www.spinics.net/lists/linux-gpio/msg10571.html
http://www.spinics.net/lists/devicetree/msg121734.html
Introduce the missing callback. Add corresponding consumer functions
such as gpiod_get_array_value(). Amend linehandle_ioctl() to take
advantage of the newly added infrastructure. Update the documentation.
Cc: Rojhalat Ibrahim <imr@rtschenk.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index d003ccb..10a48ca 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -180,6 +180,10 @@ static inline bool acpi_can_fallback_to_crs(struct acpi_device *adev,
#endif
struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip, u16 hwnum);
+int gpiod_get_array_value_complex(bool raw, bool can_sleep,
+ unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array);
void gpiod_set_array_value_complex(bool raw, bool can_sleep,
unsigned int array_size,
struct gpio_desc **desc_array,
