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: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e14eb88..453ac77 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 @@
};
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 @@
#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 @@
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 @@
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 @@
* @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 @@
const char *label;
struct device *dev;
struct module *owner;
+ struct list_head list;
int (*request)(struct gpio_chip *chip,
unsigned offset);