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>

2 files changed, 48 insertions, 0 deletions

diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 8f702fcbe485..d4920ec1f1da 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -99,10 +99,15 @@ int gpiod_direction_output_raw(struct gpio_desc *desc, int value);
 
 /* Value get/set from non-sleeping context */
 int gpiod_get_value(const struct gpio_desc *desc);
+int gpiod_get_array_value(unsigned int array_size,
+                          struct gpio_desc **desc_array, int *value_array);
 void gpiod_set_value(struct gpio_desc *desc, int value);
 void gpiod_set_array_value(unsigned int array_size,
                            struct gpio_desc **desc_array, int *value_array);
 int gpiod_get_raw_value(const struct gpio_desc *desc);
+int gpiod_get_raw_array_value(unsigned int array_size,
+                              struct gpio_desc **desc_array,
+                              int *value_array);
 void gpiod_set_raw_value(struct gpio_desc *desc, int value);
 void gpiod_set_raw_array_value(unsigned int array_size,
                                struct gpio_desc **desc_array,
@@ -110,11 +115,17 @@ void gpiod_set_raw_array_value(unsigned int array_size,
 
 /* Value get/set from sleeping context */
 int gpiod_get_value_cansleep(const struct gpio_desc *desc);
+int gpiod_get_array_value_cansleep(unsigned int array_size,
+                                   struct gpio_desc **desc_array,
+                                   int *value_array);
 void gpiod_set_value_cansleep(struct gpio_desc *desc, int value);
 void gpiod_set_array_value_cansleep(unsigned int array_size,
                                     struct gpio_desc **desc_array,
                                     int *value_array);
 int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc);
+int gpiod_get_raw_array_value_cansleep(unsigned int array_size,
+                                       struct gpio_desc **desc_array,
+                                       int *value_array);
 void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value);
 void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
                                         struct gpio_desc **desc_array,
@@ -305,6 +316,14 @@ static inline int gpiod_get_value(const struct gpio_desc *desc)
         WARN_ON(1);
         return 0;
 }
+static inline int gpiod_get_array_value(unsigned int array_size,
+                                        struct gpio_desc **desc_array,
+                                        int *value_array)
+{
+        /* GPIO can never have been requested */
+        WARN_ON(1);
+        return 0;
+}
 static inline void gpiod_set_value(struct gpio_desc *desc, int value)
 {
         /* GPIO can never have been requested */
@@ -323,6 +342,14 @@ static inline int gpiod_get_raw_value(const struct gpio_desc *desc)
         WARN_ON(1);
         return 0;
 }
+static inline int gpiod_get_raw_array_value(unsigned int array_size,
+                                            struct gpio_desc **desc_array,
+                                            int *value_array)
+{
+        /* GPIO can never have been requested */
+        WARN_ON(1);
+        return 0;
+}
 static inline void gpiod_set_raw_value(struct gpio_desc *desc, int value)
 {
         /* GPIO can never have been requested */
@@ -342,6 +369,14 @@ static inline int gpiod_get_value_cansleep(const struct gpio_desc *desc)
         WARN_ON(1);
         return 0;
 }
+static inline int gpiod_get_array_value_cansleep(unsigned int array_size,
+                                     struct gpio_desc **desc_array,
+                                     int *value_array)
+{
+        /* GPIO can never have been requested */
+        WARN_ON(1);
+        return 0;
+}
 static inline void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
 {
         /* GPIO can never have been requested */
@@ -360,6 +395,14 @@ static inline int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc)
         WARN_ON(1);
         return 0;
 }
+static inline int gpiod_get_raw_array_value_cansleep(unsigned int array_size,
+                                               struct gpio_desc **desc_array,
+                                               int *value_array)
+{
+        /* GPIO can never have been requested */
+        WARN_ON(1);
+        return 0;
+}
 static inline void gpiod_set_raw_value_cansleep(struct gpio_desc *desc,
                                                 int value)
 {
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 6bbda879fb8b..bda95a9b7b8c 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,