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 <[email protected]> --- drivers/gpio/gpiolib.c | 51 +++++++++++++++++++++++++++++++++++++++------- include/asm-generic/gpio.h | 2 ++ 2 files changed, 46 insertions(+), 7 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index e27877a..0050766 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -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 @@ -1013,6 +1016,43 @@ 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 @@ -1054,13 +1094,8 @@ 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; @@ -1134,6 +1169,8 @@ 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); diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h index 2034e69..b562f95 100644 --- a/include/asm-generic/gpio.h +++ b/include/asm-generic/gpio.h @@ -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); -- 1.8.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
