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authorAlexandre Courbot <acourbot@nvidia.com>2014-11-19 16:51:27 +0900
committerLinus Walleij <linus.walleij@linaro.org>2014-11-28 11:28:23 +0100
commit14e85c0e69d5c7fdbd963edbbec1dc5cdd385200 (patch)
tree1cd91d3c5bf4fd27c9e2c08290832e3c5cf2ce8a /drivers/gpio
parentc8aaa1bf068f76c84111671a7c13ad7b06b21997 (diff)
downloadop-kernel-dev-14e85c0e69d5c7fdbd963edbbec1dc5cdd385200.zip
op-kernel-dev-14e85c0e69d5c7fdbd963edbbec1dc5cdd385200.tar.gz
gpio: remove gpio_descs global array
Replace the ARCH_NR_GPIOS-sized static array of GPIO descriptors by dynamically-allocated arrays for each GPIO chip. This change makes gpio_to_desc() perform in O(n) (where n is the number of GPIO chips registered) instead of O(1), however since n is rarely bigger than 1 or 2 no noticeable performance issue is expected. Besides this provides more incentive for GPIO consumers to move to the gpiod interface. One could use a O(log(n)) structure to link the GPIO chips together, but considering the low limit of n the hypothetical performance benefit is probably not worth the added complexity. This patch uses kcalloc() in gpiochip_add(), which removes the ability to add a chip before kcalloc() can operate. I am not aware of such cases, but if someone bisects up to this patch then I will be proven wrong... Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/gpio')
-rw-r--r--drivers/gpio/gpiolib.c47
1 files changed, 31 insertions, 16 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 12d981a..5619922 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -47,8 +47,6 @@
*/
DEFINE_SPINLOCK(gpio_lock);
-static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
-
#define GPIO_OFFSET_VALID(chip, offset) (offset >= 0 && offset < chip->ngpio)
static DEFINE_MUTEX(gpio_lookup_lock);
@@ -65,10 +63,22 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
*/
struct gpio_desc *gpio_to_desc(unsigned gpio)
{
- if (WARN(!gpio_is_valid(gpio), "invalid GPIO %d\n", gpio))
- return NULL;
- else
- return &gpio_desc[gpio];
+ struct gpio_chip *chip;
+ unsigned long flags;
+
+ spin_lock_irqsave(&gpio_lock, flags);
+
+ list_for_each_entry(chip, &gpio_chips, list) {
+ if (chip->base <= gpio && chip->base + chip->ngpio > gpio) {
+ spin_unlock_irqrestore(&gpio_lock, flags);
+ return &chip->desc[gpio - chip->base];
+ }
+ }
+
+ spin_unlock_irqrestore(&gpio_lock, flags);
+
+ WARN(1, "invalid GPIO %d\n", gpio);
+ return NULL;
}
EXPORT_SYMBOL_GPL(gpio_to_desc);
@@ -91,7 +101,7 @@ struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip,
*/
int desc_to_gpio(const struct gpio_desc *desc)
{
- return desc - &gpio_desc[0];
+ return desc->chip->base + (desc - &desc->chip->desc[0]);
}
EXPORT_SYMBOL_GPL(desc_to_gpio);
@@ -206,7 +216,7 @@ static int gpiochip_add_to_list(struct gpio_chip *chip)
/**
* gpiochip_add() - register a gpio_chip
* @chip: the chip to register, with chip->base initialized
- * Context: potentially before irqs or kmalloc will work
+ * Context: potentially before irqs will work
*
* Returns a negative errno if the chip can't be registered, such as
* because the chip->base is invalid or already associated with a
@@ -226,12 +236,11 @@ int gpiochip_add(struct gpio_chip *chip)
int status = 0;
unsigned id;
int base = chip->base;
+ struct gpio_desc *descs;
- if (base >= 0 &&
- (!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))) {
- status = -EINVAL;
- goto fail;
- }
+ descs = kcalloc(chip->ngpio, sizeof(descs[0]), GFP_KERNEL);
+ if (!descs)
+ return -ENOMEM;
spin_lock_irqsave(&gpio_lock, flags);
@@ -247,10 +256,8 @@ int gpiochip_add(struct gpio_chip *chip)
status = gpiochip_add_to_list(chip);
if (status == 0) {
- chip->desc = &gpio_desc[chip->base];
-
for (id = 0; id < chip->ngpio; id++) {
- struct gpio_desc *desc = &chip->desc[id];
+ struct gpio_desc *desc = &descs[id];
desc->chip = chip;
/* REVISIT: most hardware initializes GPIOs as
@@ -266,6 +273,8 @@ int gpiochip_add(struct gpio_chip *chip)
}
}
+ chip->desc = descs;
+
spin_unlock_irqrestore(&gpio_lock, flags);
#ifdef CONFIG_PINCTRL
@@ -291,6 +300,9 @@ int gpiochip_add(struct gpio_chip *chip)
unlock:
spin_unlock_irqrestore(&gpio_lock, flags);
fail:
+ kfree(descs);
+ chip->desc = NULL;
+
/* failures here can mean systems won't boot... */
pr_err("%s: GPIOs %d..%d (%s) failed to register\n", __func__,
chip->base, chip->base + chip->ngpio - 1,
@@ -331,6 +343,9 @@ void gpiochip_remove(struct gpio_chip *chip)
list_del(&chip->list);
spin_unlock_irqrestore(&gpio_lock, flags);
gpiochip_unexport(chip);
+
+ kfree(chip->desc);
+ chip->desc = NULL;
}
EXPORT_SYMBOL_GPL(gpiochip_remove);
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