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/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 6bbda87..bda95a9 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -35,6 +35,8 @@ struct module;
* @direction_input: configures signal "offset" as input, or returns error
* @direction_output: configures signal "offset" as output, or returns error
* @get: returns value for signal "offset", 0=low, 1=high, or negative error
+ * @get_multiple: reads values for multiple signals defined by "mask" and
+ * stores them in "bits", returns 0 on success or negative error
* @set: assigns output value for signal "offset"
* @set_multiple: assigns output values for multiple signals defined by "mask"
* @set_config: optional hook for all kinds of settings. Uses the same
@@ -125,6 +127,9 @@ struct gpio_chip {
unsigned offset, int value);
int (*get)(struct gpio_chip *chip,
unsigned offset);
+ int (*get_multiple)(struct gpio_chip *chip,
+ unsigned long *mask,
+ unsigned long *bits);
void (*set)(struct gpio_chip *chip,
unsigned offset, int value);
void (*set_multiple)(struct gpio_chip *chip,