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gpiolib: use gpio_chips list in gpiochip_find_base

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Re-implement gpiochip_find_base using the list of chips instead of the
global gpio_desc[] array. This makes it both simpler and more efficient,
and is needed to remove the global descriptors array.

The new code should preserve the exact same GPIO number assignment
policy as the code it is replacing. There shouldn't be any visible
change to the assigned GPIO numbers.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
[grant.likely: Added comment about assignment policy]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Alexandre Courbot 2013-02-03 01:29:28 +09:00 committed by Grant Likely
parent cb1650d4e0
commit 83cabe33eb
1 changed files with 15 additions and 20 deletions
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31
drivers/gpio/gpiolib.c
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@ -126,30 +126,25 @@ struct gpio_chip *gpio_to_chip(unsigned gpio)
/* 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;
struct gpio_chip *chip;
int base = ARCH_NR_GPIOS - ngpio;
for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
struct gpio_desc *desc = &gpio_desc[i];
struct gpio_chip *chip = desc->chip;
if (!chip) {
spare++;
if (spare == ngpio) {
base = i;
list_for_each_entry_reverse(chip, &gpio_chips, list) {
/* found a free space? */
if (chip->base + chip->ngpio <= base)
break;
}
} else {
spare = 0;
if (chip)
i -= chip->ngpio - 1;
}
else
/* nope, check the space right before the chip */
base = chip->base - ngpio;
}
if (gpio_is_valid(base))
if (gpio_is_valid(base)) {
pr_debug("%s: found new base at %d\n", __func__, base);
return base;
} else {
pr_err("%s: cannot find free range\n", __func__);
return -ENOSPC;
}
}
/* caller ensures gpio is valid and requested, chip->get_direction may sleep */