From 83cabe33eb05b51a6239a3df344d89cafac2306c Mon Sep 17 00:00:00 2001
From: Alexandre Courbot <acourbot@nvidia.com>
Date: Sun, 3 Feb 2013 01:29:28 +0900
Subject: [PATCH] gpiolib: use gpio_chips list in gpiochip_find_base
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>
---
drivers/gpio/gpiolib.c | 35 +++++++++++++++--------------------
1 file changed, 15 insertions(+), 20 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 585d7c3ce12e..8ccf68bb8a40 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -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;
- break;
- }
- } else {
- spare = 0;
- if (chip)
- i -= chip->ngpio - 1;
- }
+ list_for_each_entry_reverse(chip, &gpio_chips, list) {
+ /* found a free space? */
+ if (chip->base + chip->ngpio <= base)
+ break;
+ 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;
+ 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 */