Commit 1a989d0f authored by Alexandre Courbot's avatar Alexandre Courbot Committed by Grant Likely
Browse files

gpiolib: link all gpio_chips using a list 



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: default avatarAlexandre Courbot <acourbot@nvidia.com>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent 0fa2fd9a

drivers/gpio/gpiolib.c

+44 −7
Original line number Diff line number Diff line
@@ -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);

include/asm-generic/gpio.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

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