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authorEric Miao <eric.y.miao@gmail.com>2010-03-05 21:44:35 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-06 19:26:48 (GMT)
commit3e45f1d1155894e6f4291f5536b224874d52d8e2 (patch)
treed7b44dd5248bdb053c0cd6632e82ce8893833519 /Documentation/gpio.txt
parent62fecb70cfaa9b4c6aa1981acd53b18f4ad925f0 (diff)
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>
Diffstat (limited to 'Documentation/gpio.txt')
-rw-r--r--Documentation/gpio.txt64
1 files changed, 64 insertions, 0 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 1866c27..c2c6e9b 100644
--- 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
--------------------

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