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gpiolib: rewrite gpiodev_add_to_list

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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 ef7c755303 ("gpiolib: improve overlap check of range of
    gpio").
2.  Commit 96098df125 ("gpiolib: fix chip order in gpio list")

Warning:
1.  Commit e28ecca6ea ("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: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Bamvor Jian Zhang 2016-02-26 22:37:14 +08:00 committed by Linus Walleij
parent 24030d9d95
commit a961f9b472
1 changed files with 27 additions and 42 deletions
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69
drivers/gpio/gpiolib.c
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@ -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;
}
}
previous = iterator;
}
/*
* 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.
*/
iterator = list_last_entry(&gpio_devices, struct gpio_device, list);
if (iterator->base + iterator->ngpio <= gdev->base) {
list_add(&gdev->list, &iterator->list);
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;
}
dev_err(&gdev->dev,
"GPIO integer space overlap, cannot add chip\n");
return -EBUSY;
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;
}
found:
list_add_tail(&gdev->list, &iterator->list);
return 0;
list_for_each_entry_safe(prev, next, &gpio_devices, list) {
/* at the end of the list */
if (&next->list == &gpio_devices)
break;
/* 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");
return -EBUSY;
}
/**