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Commit a961f9b4 authored by Bamvor Jian Zhang's avatar Bamvor Jian Zhang Committed by Linus Walleij
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gpiolib: rewrite gpiodev_add_to_list 

The original code of gpiodev_add_to_list is not very clear which
lead to bugs or compiling warning, reference the following patches:
Bugs:
1.  Commit ef7c7553 ("gpiolib: improve overlap check of range of
    gpio").
2.  Commit 96098df1 ("gpiolib: fix chip order in gpio list")

Warning:
1.  Commit e28ecca6 ("gpio: fix warning about iterator").
of gpio").

There is a off-list discussion about how to improve it consequently.
This commit try to follow this by rewriting the whole functions.

Tested pass with my gpio mockup driver and test scripts[1].

[1] http://www.spinics.net/lists/linux-gpio/msg09598.html



Suggested-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarBamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 24030d9d

drivers/gpio/gpiolib.c

+25 −40
Original line number Diff line number Diff line
@@ -206,58 +206,43 @@ EXPORT_SYMBOL_GPL(gpiod_get_direction); 
 */

static int gpiodev_add_to_list(struct gpio_device *gdev)

{

	struct gpio_device *iterator;

	struct gpio_device *previous = NULL;



	if (!gdev->chip)

		return -EINVAL;

	struct gpio_device *prev, *next;



	if (list_empty(&gpio_devices)) {

		/* initial entry in list */

		list_add_tail(&gdev->list, &gpio_devices);

		return 0;

	}



	list_for_each_entry(iterator, &gpio_devices, list) {

		if (iterator->base >= gdev->base + gdev->ngpio) {

			/*

			 * Iterator is the first GPIO chip so there is no

			 * previous one

			 */

			if (!previous) {

				goto found;

			} else {

				/*

				 * We found a valid range(means

				 * [base, base + ngpio - 1]) between previous

				 * and iterator chip.

				 */

				if (previous->base + previous->ngpio

				    <= gdev->base)

					goto found;

			}

	next = list_entry(gpio_devices.next, struct gpio_device, list);

	if (gdev->base + gdev->ngpio <= next->base) {

		/* add before first entry */

		list_add(&gdev->list, &gpio_devices);

		return 0;

	}

		previous = iterator;



	prev = list_entry(gpio_devices.prev, struct gpio_device, list);

	if (prev->base + prev->ngpio <= gdev->base) {

		/* add behind last entry */

		list_add_tail(&gdev->list, &gpio_devices);

		return 0;

	}



	/*

	 * We are beyond the last chip in the list and iterator now

	 * points to the head.

	 * Let iterator point to the last chip in the list.

	 */

	list_for_each_entry_safe(prev, next, &gpio_devices, list) {

		/* at the end of the list */

		if (&next->list == &gpio_devices)

			break;



	iterator = list_last_entry(&gpio_devices, struct gpio_device, list);

	if (iterator->base + iterator->ngpio <= gdev->base) {

		list_add(&gdev->list, &iterator->list);

		/* add between prev and next */

		if (prev->base + prev->ngpio <= gdev->base

				&& gdev->base + gdev->ngpio <= next->base) {

			list_add(&gdev->list, &prev->list);

			return 0;

		}

	}



	dev_err(&gdev->dev,

	       "GPIO integer space overlap, cannot add chip\n");

	dev_err(&gdev->dev, "GPIO integer space overlap, cannot add chip\n");

	return -EBUSY;



found:

	list_add_tail(&gdev->list, &iterator->list);

	return 0;

}



/**