diff options
| -rw-r--r-- | drivers/gpio/gpiolib.c | 52 |
1 files changed, 45 insertions, 7 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 623fcd9..2ba6127 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... */ |