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gpiolib: link all gpio_chips using a list

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Add a list member to gpio_chip that allows all chips to be parsed
quickly. The current method requires parsing the entire GPIO integer
space, which is painfully slow. Using a list makes many chip operations
that involve lookup or parsing faster, and also simplifies the code. It
is also necessary to eventually get rid of the global gpio_desc[] array.

The list of gpio_chips is always ordered by base GPIO number to ensure
chips traversal is done in the right order.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Alexandre Courbot 2013-02-03 01:29:24 +09:00 committed by Grant Likely
parent 0fa2fd9a0d
commit 1a989d0f1d
2 changed files with 46 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
drivers/gpio/gpiolib.c
View File

@ -3,6 +3,7 @@
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/debugfs.h>
@ -71,6 +72,8 @@ struct gpio_desc {
};
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
static LIST_HEAD(gpio_chips);
#ifdef CONFIG_GPIO_SYSFS
static DEFINE_IDR(dirent_idr);
#endif
@ -1014,6 +1017,43 @@ static inline void gpiochip_unexport(struct gpio_chip *chip)
#endif /* CONFIG_GPIO_SYSFS */
/*
* Add a new chip to the global chips list, keeping the list of chips sorted
* by base order.
*
* Return -EBUSY if the new chip overlaps with some other chip's integer
* space.
*/
static int gpiochip_add_to_list(struct gpio_chip *chip)
{
struct list_head *pos = &gpio_chips;
struct gpio_chip *_chip;
int err = 0;
/* find where to insert our chip */
list_for_each(pos, &gpio_chips) {
_chip = list_entry(pos, struct gpio_chip, list);
/* shall we insert before _chip? */
if (_chip->base >= chip->base + chip->ngpio)
break;
}
/* are we stepping on the chip right before? */
if (pos != &gpio_chips && pos->prev != &gpio_chips) {
_chip = list_entry(pos->prev, struct gpio_chip, list);
if (_chip->base + _chip->ngpio > chip->base) {
dev_err(chip->dev,
"GPIO integer space overlap, cannot add chip\n");
err = -EBUSY;
}
}
if (!err)
list_add_tail(&chip->list, pos);
return err;
}
/**
* gpiochip_add() - register a gpio_chip
* @chip: the chip to register, with chip->base initialized
@ -1055,13 +1095,8 @@ int gpiochip_add(struct gpio_chip *chip)
chip->base = base;
}
/* these GPIO numbers must not be managed by another gpio_chip */
for (id = base; id < base + chip->ngpio; id++) {
if (gpio_desc[id].chip != NULL) {
status = -EBUSY;
break;
}
}
status = gpiochip_add_to_list(chip);
if (status == 0) {
for (id = base; id < base + chip->ngpio; id++) {
gpio_desc[id].chip = chip;
@ -1135,6 +1170,8 @@ int gpiochip_remove(struct gpio_chip *chip)
if (status == 0) {
for (id = chip->base; id < chip->base + chip->ngpio; id++)
gpio_desc[id].chip = NULL;
list_del(&chip->list);
}
spin_unlock_irqrestore(&gpio_lock, flags);

2
include/asm-generic/gpio.h
View File

@ -53,6 +53,7 @@ struct device_node;
* @label: for diagnostics
* @dev: optional device providing the GPIOs
* @owner: helps prevent removal of modules exporting active GPIOs
* @list: links gpio_chips together for traversal
* @request: optional hook for chip-specific activation, such as
* enabling module power and clock; may sleep
* @free: optional hook for chip-specific deactivation, such as
@ -98,6 +99,7 @@ struct gpio_chip {
const char *label;
struct device *dev;
struct module *owner;
struct list_head list;
int (*request)(struct gpio_chip *chip,
unsigned offset);