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authorAnton Vorontsov <avorontsov@ru.mvista.com>2008-04-28 02:14:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-28 08:58:34 -0700
commit8d0aab2f16c4fa170f32e7a74a52cd0122bbafef (patch)
treec9e559489af8f2cbcceda8a323e4ac496114765a
parente6de1808f8ebfeb7e49f3c5a30cb8f2032beb287 (diff)
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gpiolib: dynamic gpio number allocation
If gpio_chip->base is negative during registration, gpiolib performs dynamic base allocation. This is useful for devices that aren't always present, such as GPIOs on hotplugged devices rather than mainboards. (This behavior was previously specified but not implemented.) To avoid using any numbers that may have been explicitly assigned but not yet registered, this dynamic allocation assigns GPIO numbers from the biggest number on down, instead of from the smallest on up. Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/gpio/gpiolib.c52
1 files changed, 45 insertions, 7 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 623fcd9b547..2ba6127c4fa 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -80,6 +80,33 @@ static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
return gpio_desc[gpio].chip;
}
+/* dynamic allocation of GPIOs, e.g. on a hotplugged device */
+static int gpiochip_find_base(int ngpio)
+{
+ int i;
+ int spare = 0;
+ int base = -ENOSPC;
+
+ for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
+ struct gpio_chip *chip = gpio_desc[i].chip;
+
+ if (!chip) {
+ spare++;
+ if (spare == ngpio) {
+ base = i;
+ break;
+ }
+ } else {
+ spare = 0;
+ i -= chip->ngpio - 1;
+ }
+ }
+
+ if (gpio_is_valid(base))
+ pr_debug("%s: found new base at %d\n", __func__, base);
+ return base;
+}
+
/**
* gpiochip_add() - register a gpio_chip
* @chip: the chip to register, with chip->base initialized
@@ -88,38 +115,49 @@ static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
* Returns a negative errno if the chip can't be registered, such as
* because the chip->base is invalid or already associated with a
* different chip. Otherwise it returns zero as a success code.
+ *
+ * If chip->base is negative, this requests dynamic assignment of
+ * a range of valid GPIOs.
*/
int gpiochip_add(struct gpio_chip *chip)
{
unsigned long flags;
int status = 0;
unsigned id;
+ int base = chip->base;
- /* NOTE chip->base negative is reserved to mean a request for
- * dynamic allocation. We don't currently support that.
- */
-
- if (chip->base < 0 || !gpio_is_valid(chip->base + chip->ngpio)) {
+ if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio))
+ && base >= 0) {
status = -EINVAL;
goto fail;
}
spin_lock_irqsave(&gpio_lock, flags);
+ if (base < 0) {
+ base = gpiochip_find_base(chip->ngpio);
+ if (base < 0) {
+ status = base;
+ goto fail_unlock;
+ }
+ chip->base = base;
+ }
+
/* these GPIO numbers must not be managed by another gpio_chip */
- for (id = chip->base; id < chip->base + chip->ngpio; id++) {
+ for (id = base; id < base + chip->ngpio; id++) {
if (gpio_desc[id].chip != NULL) {
status = -EBUSY;
break;
}
}
if (status == 0) {
- for (id = chip->base; id < chip->base + chip->ngpio; id++) {
+ for (id = base; id < base + chip->ngpio; id++) {
gpio_desc[id].chip = chip;
gpio_desc[id].flags = 0;
}
}
+fail_unlock:
spin_unlock_irqrestore(&gpio_lock, flags);
fail:
/* failures here can mean systems won't boot... */