gpio: introduce gpio_request_one() and friends

gpio_request() without initial configuration of the GPIO is normally
useless, introduce gpio_request_one() together with GPIOF_ flags for
input/output direction and initial output level.

gpio_{request,free}_array() for multiple GPIOs.

Signed-off-by: Eric Miao <eric.y.miao@gmail.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Ben Nizette <bn@niasdigital.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 1866c27..c2c6e9b 100644 (file)
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -253,6 +253,70 @@ pin setup (e.g. controlling which pin the GPIO uses, pullup/pulldown).
 Also note that it's your responsibility to have stopped using a GPIO
 before you free it.
 
+Considering in most cases GPIOs are actually configured right after they
+are claimed, three additional calls are defined:
+
+       /* request a single GPIO, with initial configuration specified by
+        * 'flags', identical to gpio_request() wrt other arguments and
+        * return value
+        */
+       int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
+
+       /* request multiple GPIOs in a single call
+        */
+       int gpio_request_array(struct gpio *array, size_t num);
+
+       /* release multiple GPIOs in a single call
+        */
+       void gpio_free_array(struct gpio *array, size_t num);
+
+where 'flags' is currently defined to specify the following properties:
+
+       * GPIOF_DIR_IN          - to configure direction as input
+       * GPIOF_DIR_OUT         - to configure direction as output
+
+       * GPIOF_INIT_LOW        - as output, set initial level to LOW
+       * GPIOF_INIT_HIGH       - as output, set initial level to HIGH
+
+since GPIOF_INIT_* are only valid when configured as output, so group valid
+combinations as:
+
+       * GPIOF_IN              - configure as input
+       * GPIOF_OUT_INIT_LOW    - configured as output, initial level LOW
+       * GPIOF_OUT_INIT_HIGH   - configured as output, initial level HIGH
+
+In the future, these flags can be extended to support more properties such
+as open-drain status.
+
+Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
+introduced to encapsulate all three fields as:
+
+       struct gpio {
+               unsigned        gpio;
+               unsigned long   flags;
+               const char      *label;
+       };
+
+A typical example of usage:
+
+       static struct gpio leds_gpios[] = {
+               { 32, GPIOF_OUT_INIT_HIGH, "Power LED" }, /* default to ON */
+               { 33, GPIOF_OUT_INIT_LOW,  "Green LED" }, /* default to OFF */
+               { 34, GPIOF_OUT_INIT_LOW,  "Red LED"   }, /* default to OFF */
+               { 35, GPIOF_OUT_INIT_LOW,  "Blue LED"  }, /* default to OFF */
+               { ... },
+       };
+
+       err = gpio_request_one(31, GPIOF_IN, "Reset Button");
+       if (err)
+               ...
+
+       err = gpio_request_array(leds_gpios, ARRAY_SIZE(leds_gpios));
+       if (err)
+               ...
+
+       gpio_free_array(leds_gpios, ARRAY_SIZE(leds_gpios));
+
 
 GPIOs mapped to IRQs
 --------------------

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 350842a..9006fdb 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1237,6 +1237,64 @@ void gpio_free(unsigned gpio)
 }
 EXPORT_SYMBOL_GPL(gpio_free);
 
+/**
+ * gpio_request_one - request a single GPIO with initial configuration
+ * @gpio:      the GPIO number
+ * @flags:     GPIO configuration as specified by GPIOF_*
+ * @label:     a literal description string of this GPIO
+ */
+int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
+{
+       int err;
+
+       err = gpio_request(gpio, label);
+       if (err)
+               return err;
+
+       if (flags & GPIOF_DIR_IN)
+               err = gpio_direction_input(gpio);
+       else
+               err = gpio_direction_output(gpio,
+                               (flags & GPIOF_INIT_HIGH) ? 1 : 0);
+
+       return err;
+}
+EXPORT_SYMBOL_GPL(gpio_request_one);
+
+/**
+ * gpio_request_array - request multiple GPIOs in a single call
+ * @array:     array of the 'struct gpio'
+ * @num:       how many GPIOs in the array
+ */
+int gpio_request_array(struct gpio *array, size_t num)
+{
+       int i, err;
+
+       for (i = 0; i < num; i++, array++) {
+               err = gpio_request_one(array->gpio, array->flags, array->label);
+               if (err)
+                       goto err_free;
+       }
+       return 0;
+
+err_free:
+       while (i--)
+               gpio_free((--array)->gpio);
+       return err;
+}
+EXPORT_SYMBOL_GPL(gpio_request_array);
+
+/**
+ * gpio_free_array - release multiple GPIOs in a single call
+ * @array:     array of the 'struct gpio'
+ * @num:       how many GPIOs in the array
+ */
+void gpio_free_array(struct gpio *array, size_t num)
+{
+       while (num--)
+               gpio_free((array++)->gpio);
+}
+EXPORT_SYMBOL_GPL(gpio_free_array);
 
 /**
  * gpiochip_is_requested - return string iff signal was requested

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 485eeb6..979c6a5 100644 (file)
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -136,6 +136,32 @@ extern int __gpio_cansleep(unsigned gpio);
 
 extern int __gpio_to_irq(unsigned gpio);
 
+#define GPIOF_DIR_OUT  (0 << 0)
+#define GPIOF_DIR_IN   (1 << 0)
+
+#define GPIOF_INIT_LOW (0 << 1)
+#define GPIOF_INIT_HIGH        (1 << 1)
+
+#define GPIOF_IN               (GPIOF_DIR_IN)
+#define GPIOF_OUT_INIT_LOW     (GPIOF_DIR_OUT | GPIOF_INIT_LOW)
+#define GPIOF_OUT_INIT_HIGH    (GPIOF_DIR_OUT | GPIOF_INIT_HIGH)
+
+/**
+ * struct gpio - a structure describing a GPIO with configuration
+ * @gpio:      the GPIO number
+ * @flags:     GPIO configuration as specified by GPIOF_*
+ * @label:     a literal description string of this GPIO
+ */
+struct gpio {
+       unsigned        gpio;
+       unsigned long   flags;
+       const char      *label;
+};
+
+extern int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
+extern int gpio_request_array(struct gpio *array, size_t num);
+extern void gpio_free_array(struct gpio *array, size_t num);
+
 #ifdef CONFIG_GPIO_SYSFS
 
 /*