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#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <asm/gpio.h>
/* Optional implementation infrastructure for GPIO interfaces.
*
* Platforms may want to use this if they tend to use very many GPIOs
* that aren't part of a System-On-Chip core; or across I2C/SPI/etc.
*
* When kernel footprint or instruction count is an issue, simpler
* implementations may be preferred. The GPIO programming interface
* allows for inlining speed-critical get/set operations for common
* cases, so that access to SOC-integrated GPIOs can sometimes cost
* only an instruction or two per bit.
*/
/* When debugging, extend minimal trust to callers and platform code.
* Also emit diagnostic messages that may help initial bringup, when
* board setup or driver bugs are most common.
*
* Otherwise, minimize overhead in what may be bitbanging codepaths.
*/
#ifdef DEBUG
#define extra_checks 1
#else
#define extra_checks 0
#endif
/* gpio_lock prevents conflicts during gpio_desc[] table updates.
* While any GPIO is requested, its gpio_chip is not removable;
* each GPIO's "requested" flag serves as a lock and refcount.
*/
static DEFINE_SPINLOCK(gpio_lock);
struct gpio_desc {
struct gpio_chip *chip;
unsigned long flags;
/* flag symbols are bit numbers */
#define FLAG_REQUESTED 0
#define FLAG_IS_OUT 1
#ifdef CONFIG_DEBUG_FS
const char *label;
#endif
};
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
static inline void desc_set_label(struct gpio_desc *d, const char *label)
{
#ifdef CONFIG_DEBUG_FS
d->label = label;
#endif
}
/* Warn when drivers omit gpio_request() calls -- legal but ill-advised
* when setting direction, and otherwise illegal. Until board setup code
* and drivers use explicit requests everywhere (which won't happen when
* those calls have no teeth) we can't avoid autorequesting. This nag
* message should motivate switching to explicit requests...
*/
static void gpio_ensure_requested(struct gpio_desc *desc)
{
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
desc_set_label(desc, "[auto]");
}
}
/* caller holds gpio_lock *OR* gpio is marked as requested */
static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
{
return gpio_desc[gpio].chip;
}
/**
* gpiochip_add() - register a gpio_chip
* @chip: the chip to register, with chip->base initialized
* Context: potentially before irqs or kmalloc will work
*
* Returns a negative errno if the chip can't be registered, such as
* because the chip->base is invalid or already associated with a
* different chip. Otherwise it returns zero as a success code.
*/
int gpiochip_add(struct gpio_chip *chip)
{
unsigned long flags;
int status = 0;
unsigned id;
/* NOTE chip->base negative is reserved to mean a request for
* dynamic allocation. We don't currently support that.
*/
if (chip->base < 0 || (chip->base + chip->ngpio) >= ARCH_NR_GPIOS) {
status = -EINVAL;
goto fail;
}
spin_lock_irqsave(&gpio_lock, flags);
/* these GPIO numbers must not be managed by another gpio_chip */
for (id = chip->base; id < chip->base + chip->ngpio; id++) {
if (gpio_desc[id].chip != NULL) {
status = -EBUSY;
break;
}
}
if (status == 0) {
for (id = chip->base; id < chip->base + chip->ngpio; id++) {
gpio_desc[id].chip = chip;
gpio_desc[id].flags = 0;
}
}
spin_unlock_irqrestore(&gpio_lock, flags);
fail:
/* failures here can mean systems won't boot... */
if (status)
pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
chip->base, chip->base + chip->ngpio,
chip->label ? : "generic");
return status;
}
EXPORT_SYMBOL_GPL(gpiochip_add);
/**
* gpiochip_remove() - unregister a gpio_chip
* @chip: the chip to unregister
*
* A gpio_chip with any GPIOs still requested may not be removed.
*/
int gpiochip_remove(struct gpio_chip *chip)
{
unsigned long flags;
int status = 0;
unsigned id;
spin_lock_irqsave(&gpio_lock, flags);
for (id = chip->base; id < chip->base + chip->ngpio; id++) {
if (test_bit(FLAG_REQUESTED, &gpio_desc[id].flags)) {
status = -EBUSY;
break;
}
}
if (status == 0) {
for (id = chip->base; id < chip->base + chip->ngpio; id++)
gpio_desc[id].chip = NULL;
}
spin_unlock_irqrestore(&gpio_lock, flags);
return status;
}
EXPORT_SYMBOL_GPL(gpiochip_remove);
/* These "optional" allocation calls help prevent drivers from stomping
* on each other, and help provide better diagnostics in debugfs.
* They're called even less than the "set direction" calls.
*/
int gpio_request(unsigned gpio, const char *label)
{
struct gpio_desc *desc;
int status = -EINVAL;
unsigned long flags;
spin_lock_irqsave(&gpio_lock, flags);
if (gpio >= ARCH_NR_GPIOS)
goto done;
desc = &gpio_desc[gpio];
if (desc->chip == NULL)
goto done;
/* NOTE: gpio_request() can be called in early boot,
* before IRQs are enabled.
*/
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
desc_set_label(desc, label ? : "?");
status = 0;
} else
status = -EBUSY;
done:
if (status)
pr_debug("gpio_request: gpio-%d (%s) status %d\n",
gpio, label ? : "?", status);
spin_unlock_irqrestore(&gpio_lock, flags);
return status;
}
EXPORT_SYMBOL_GPL(gpio_request);
void gpio_free(unsigned gpio)
{
unsigned long flags;
struct gpio_desc *desc;
if (gpio >= ARCH_NR_GPIOS) {
WARN_ON(extra_checks);
return;
}
spin_lock_irqsave(&gpio_lock, flags);
desc = &gpio_desc[gpio];
if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags))
desc_set_label(desc, NULL);
else
WARN_ON(extra_checks);
spin_unlock_irqrestore(&gpio_lock, flags);
}
EXPORT_SYMBOL_GPL(gpio_free);
/**
* gpiochip_is_requested - return string iff signal was requested
* @chip: controller managing the signal
* @offset: of signal within controller's 0..(ngpio - 1) range
*
* Returns NULL if the GPIO is not currently requested, else a string.
* If debugfs support is enabled, the string returned is the label passed
* to gpio_request(); otherwise it is a meaningless constant.
*
* This function is for use by GPIO controller drivers. The label can
* help with diagnostics, and knowing that the signal is used as a GPIO
* can help avoid accidentally multiplexing it to another controller.
*/
const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset)
{
unsigned gpio = chip->base + offset;
if (gpio >= ARCH_NR_GPIOS || gpio_desc[gpio].chip != chip)
return NULL;
if (test_bit(FLAG_REQUESTED, &gpio_desc[gpio].flags) == 0)
return NULL;
#ifdef CONFIG_DEBUG_FS
return gpio_desc[gpio].label;
#else
return "?";
#endif
}
EXPORT_SYMBOL_GPL(gpiochip_is_requested);
/* Drivers MUST set GPIO direction before making get/set calls. In
* some cases this is done in early boot, before IRQs are enabled.
*
* As a rule these aren't called more than once (except for drivers
* using the open-drain emulation idiom) so these are natural places
* to accumulate extra debugging checks. Note that we can't (yet)
* rely on gpio_request() having been called beforehand.
*/
int gpio_direction_input(unsigned gpio)
{
unsigned long flags;
struct gpio_chip *chip;
struct gpio_desc *desc = &gpio_desc[gpio];
int status = -EINVAL;
spin_lock_irqsave(&gpio_lock, flags);
if (gpio >= ARCH_NR_GPIOS)
goto fail;
chip = desc->chip;
if (!chip || !chip->get || !chip->direction_input)
goto fail;
gpio -= chip->base;
if (gpio >= chip->ngpio)
|