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path: root/drivers/gpio/gpiolib.c
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Diffstat (limited to 'drivers/gpio/gpiolib.c')
-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... */