gpiolib: request/free hooks
Add a new internal mechanism to gpiolib to support low power operations by letting gpio_chip instances see when their GPIOs are in use. When no GPIOs are active, chips may be able to enter lower powered runtime states by disabling clocks and/or power domains. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: "Magnus Damm" <magnus.damm@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Brownell
Linus Torvalds
Родитель
93a22f8b95
Коммит
35e8bb5175
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@ -240,6 +240,10 @@ signal, or (b) something wrongly believes it's safe to remove drivers
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needed to manage a signal that's in active use. That is, requesting a
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GPIO can serve as a kind of lock.
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Some platforms may also use knowledge about what GPIOs are active for
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power management, such as by powering down unused chip sectors and, more
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easily, gating off unused clocks.
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These two calls are optional because not not all current Linux platforms
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offer such functionality in their GPIO support; a valid implementation
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could return success for all gpio_request() calls. Unlike the other calls,
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@ -67,17 +67,28 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
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* when setting direction, and otherwise illegal. Until board setup code
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* and drivers use explicit requests everywhere (which won't happen when
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* those calls have no teeth) we can't avoid autorequesting. This nag
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* message should motivate switching to explicit requests...
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* message should motivate switching to explicit requests... so should
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* the weaker cleanup after faults, compared to gpio_request().
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*/
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static void gpio_ensure_requested(struct gpio_desc *desc)
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static int gpio_ensure_requested(struct gpio_desc *desc, unsigned offset)
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{
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if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
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pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
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struct gpio_chip *chip = desc->chip;
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int gpio = chip->base + offset;
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if (!try_module_get(chip->owner)) {
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pr_err("GPIO-%d: module can't be gotten \n", gpio);
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clear_bit(FLAG_REQUESTED, &desc->flags);
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/* lose */
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return -EIO;
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}
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pr_warning("GPIO-%d autorequested\n", gpio);
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desc_set_label(desc, "[auto]");
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if (!try_module_get(desc->chip->owner))
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pr_err("GPIO-%d: module can't be gotten \n",
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(int)(desc - gpio_desc));
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/* caller must chip->request() w/o spinlock */
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if (chip->request)
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return 1;
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}
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return 0;
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}
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/* caller holds gpio_lock *OR* gpio is marked as requested */
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@ -752,6 +763,7 @@ EXPORT_SYMBOL_GPL(gpiochip_remove);
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int gpio_request(unsigned gpio, const char *label)
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{
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struct gpio_desc *desc;
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struct gpio_chip *chip;
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int status = -EINVAL;
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unsigned long flags;
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@ -760,14 +772,15 @@ int gpio_request(unsigned gpio, const char *label)
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if (!gpio_is_valid(gpio))
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goto done;
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desc = &gpio_desc[gpio];
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if (desc->chip == NULL)
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chip = desc->chip;
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if (chip == NULL)
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goto done;
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if (!try_module_get(desc->chip->owner))
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if (!try_module_get(chip->owner))
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goto done;
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/* NOTE: gpio_request() can be called in early boot,
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* before IRQs are enabled.
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* before IRQs are enabled, for non-sleeping (SOC) GPIOs.
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*/
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if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
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@ -775,7 +788,20 @@ int gpio_request(unsigned gpio, const char *label)
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status = 0;
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} else {
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status = -EBUSY;
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module_put(desc->chip->owner);
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module_put(chip->owner);
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}
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if (chip->request) {
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/* chip->request may sleep */
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spin_unlock_irqrestore(&gpio_lock, flags);
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status = chip->request(chip, gpio - chip->base);
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spin_lock_irqsave(&gpio_lock, flags);
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if (status < 0) {
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desc_set_label(desc, NULL);
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module_put(chip->owner);
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clear_bit(FLAG_REQUESTED, &desc->flags);
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}
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}
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done:
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@ -791,6 +817,7 @@ void gpio_free(unsigned gpio)
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{
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unsigned long flags;
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struct gpio_desc *desc;
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struct gpio_chip *chip;
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might_sleep();
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@ -804,9 +831,17 @@ void gpio_free(unsigned gpio)
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spin_lock_irqsave(&gpio_lock, flags);
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desc = &gpio_desc[gpio];
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if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {
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chip = desc->chip;
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if (chip && test_bit(FLAG_REQUESTED, &desc->flags)) {
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if (chip->free) {
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spin_unlock_irqrestore(&gpio_lock, flags);
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might_sleep_if(extra_checks && chip->can_sleep);
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chip->free(chip, gpio - chip->base);
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spin_lock_irqsave(&gpio_lock, flags);
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}
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desc_set_label(desc, NULL);
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module_put(desc->chip->owner);
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clear_bit(FLAG_REQUESTED, &desc->flags);
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} else
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WARN_ON(extra_checks);
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@ -871,7 +906,9 @@ int gpio_direction_input(unsigned gpio)
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gpio -= chip->base;
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if (gpio >= chip->ngpio)
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goto fail;
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gpio_ensure_requested(desc);
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status = gpio_ensure_requested(desc, gpio);
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if (status < 0)
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goto fail;
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/* now we know the gpio is valid and chip won't vanish */
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@ -879,9 +916,22 @@ int gpio_direction_input(unsigned gpio)
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might_sleep_if(extra_checks && chip->can_sleep);
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if (status) {
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status = chip->request(chip, gpio);
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if (status < 0) {
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pr_debug("GPIO-%d: chip request fail, %d\n",
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chip->base + gpio, status);
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/* and it's not available to anyone else ...
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* gpio_request() is the fully clean solution.
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*/
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goto lose;
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}
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}
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status = chip->direction_input(chip, gpio);
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if (status == 0)
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clear_bit(FLAG_IS_OUT, &desc->flags);
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lose:
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return status;
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fail:
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spin_unlock_irqrestore(&gpio_lock, flags);
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@ -909,7 +959,9 @@ int gpio_direction_output(unsigned gpio, int value)
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gpio -= chip->base;
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if (gpio >= chip->ngpio)
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goto fail;
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gpio_ensure_requested(desc);
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status = gpio_ensure_requested(desc, gpio);
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if (status < 0)
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goto fail;
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/* now we know the gpio is valid and chip won't vanish */
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@ -917,9 +969,22 @@ int gpio_direction_output(unsigned gpio, int value)
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might_sleep_if(extra_checks && chip->can_sleep);
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if (status) {
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status = chip->request(chip, gpio);
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if (status < 0) {
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pr_debug("GPIO-%d: chip request fail, %d\n",
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chip->base + gpio, status);
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/* and it's not available to anyone else ...
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* gpio_request() is the fully clean solution.
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*/
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goto lose;
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}
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}
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status = chip->direction_output(chip, gpio, value);
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if (status == 0)
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set_bit(FLAG_IS_OUT, &desc->flags);
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lose:
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return status;
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fail:
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spin_unlock_irqrestore(&gpio_lock, flags);
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@ -35,6 +35,10 @@ struct module;
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* @label: for diagnostics
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* @dev: optional device providing the GPIOs
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* @owner: helps prevent removal of modules exporting active GPIOs
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* @request: optional hook for chip-specific activation, such as
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* enabling module power and clock; may sleep
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* @free: optional hook for chip-specific deactivation, such as
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* disabling module power and clock; may sleep
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* @direction_input: configures signal "offset" as input, or returns error
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* @get: returns value for signal "offset"; for output signals this
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* returns either the value actually sensed, or zero
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@ -67,6 +71,11 @@ struct gpio_chip {
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struct device *dev;
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struct module *owner;
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int (*request)(struct gpio_chip *chip,
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unsigned offset);
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void (*free)(struct gpio_chip *chip,
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unsigned offset);
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int (*direction_input)(struct gpio_chip *chip,
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unsigned offset);
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int (*get)(struct gpio_chip *chip,
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