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Commit d468bf9e authored by Linus Walleij's avatar Linus Walleij
Browse files

gpio: add API to be strict about GPIO IRQ usage 



It is currently often possible in many GPIO drivers to request
a GPIO line to be used as IRQ after calling gpio_to_irq() and,
as the gpiolib is not aware of this, set the same line to
output and start driving it, with undesired side effects.

As it is a bogus usage scenario to request a line flagged as
output to used as IRQ, we introduce APIs to let gpiolib track
the use of a line as IRQ, and also set this flag from the
userspace ABI.

The API is symmetric so that lines can also be flagged from
.irq_enable() and unflagged from IRQ by .irq_disable().
The debugfs file is altered so that we see if a line is
reserved for IRQ.

Cc: Enric Balletbo i Serra <eballetbo@gmail.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Reviewed-by: default avatarStephen Warren <swarren@nvidia.com>
Reviewed-by: default avatarJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent d27e06ac

drivers/gpio/gpiolib.c

+86 −2
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ struct gpio_desc { 
#define FLAG_ACTIVE_LOW	6	/* sysfs value has active low */

#define FLAG_OPEN_DRAIN	7	/* Gpio is open drain type */

#define FLAG_OPEN_SOURCE 8	/* Gpio is open source type */

#define FLAG_USED_AS_IRQ 9	/* GPIO is connected to an IRQ */



#define ID_SHIFT	16	/* add new flags before this one */
@@ -96,6 +97,8 @@ static int gpiod_get_value(const struct gpio_desc *desc); 
static void gpiod_set_value(struct gpio_desc *desc, int value);

static int gpiod_cansleep(const struct gpio_desc *desc);

static int gpiod_to_irq(const struct gpio_desc *desc);

static int gpiod_lock_as_irq(struct gpio_desc *desc);

static void gpiod_unlock_as_irq(struct gpio_desc *desc);

static int gpiod_export(struct gpio_desc *desc, bool direction_may_change);

static int gpiod_export_link(struct device *dev, const char *name,

			     struct gpio_desc *desc);
@@ -162,6 +165,17 @@ static struct gpio_desc *gpio_to_desc(unsigned gpio) 
		return &gpio_desc[gpio];

}



/**

 * Convert an offset on a certain chip to a corresponding descriptor

 */

static struct gpio_desc *gpiochip_offset_to_desc(struct gpio_chip *chip,

						 unsigned int offset)

{

	unsigned int gpio = chip->base + offset;



	return gpio_to_desc(gpio);

}



/**

 * Convert a GPIO descriptor to the integer namespace.

 * This should disappear in the future but is needed since we still
@@ -428,6 +442,7 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev, 
	desc->flags &= ~GPIO_TRIGGER_MASK;



	if (!gpio_flags) {

		gpiod_unlock_as_irq(desc);

		ret = 0;

		goto free_id;

	}
@@ -466,6 +481,12 @@ static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev, 
	if (ret < 0)

		goto free_id;



	ret = gpiod_lock_as_irq(desc);

	if (ret < 0) {

		gpiod_warn(desc, "failed to flag the GPIO for IRQ\n");

		goto free_id;

	}



	desc->flags |= gpio_flags;

	return 0;
@@ -1730,6 +1751,14 @@ static int gpiod_direction_output(struct gpio_desc *desc, int value) 
		return -EINVAL;

	}



	/* GPIOs used for IRQs shall not be set as output */

	if (test_bit(FLAG_USED_AS_IRQ, &desc->flags)) {

		gpiod_err(desc,

			  "%s: tried to set a GPIO tied to an IRQ as output\n",

			  __func__);

		return -EIO;

	}



	/* Open drain pin should not be driven to 1 */

	if (value && test_bit(FLAG_OPEN_DRAIN,  &desc->flags))

		return gpiod_direction_input(desc);
@@ -2050,6 +2079,58 @@ int __gpio_to_irq(unsigned gpio) 
}

EXPORT_SYMBOL_GPL(__gpio_to_irq);



/**

 * gpiod_lock_as_irq() - lock a GPIO to be used as IRQ

 * @gpio: the GPIO line to lock as used for IRQ

 *

 * This is used directly by GPIO drivers that want to lock down

 * a certain GPIO line to be used as IRQs, for example in the

 * .to_irq() callback of their gpio_chip, or in the .irq_enable()

 * of its irq_chip implementation if the GPIO is known from that

 * code.

 */

static int gpiod_lock_as_irq(struct gpio_desc *desc)

{

	if (!desc)

		return -EINVAL;



	if (test_bit(FLAG_IS_OUT, &desc->flags)) {

		gpiod_err(desc,

			  "%s: tried to flag a GPIO set as output for IRQ\n",

			  __func__);

		return -EIO;

	}



	set_bit(FLAG_USED_AS_IRQ, &desc->flags);

	return 0;

}



int gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset)

{

	return gpiod_lock_as_irq(gpiochip_offset_to_desc(chip, offset));

}

EXPORT_SYMBOL_GPL(gpio_lock_as_irq);



/**

 * gpiod_unlock_as_irq() - unlock a GPIO used as IRQ

 * @gpio: the GPIO line to unlock from IRQ usage

 *

 * This is used directly by GPIO drivers that want to indicate

 * that a certain GPIO is no longer used exclusively for IRQ.

 */

static void gpiod_unlock_as_irq(struct gpio_desc *desc)

{

	if (!desc)

		return;



	clear_bit(FLAG_USED_AS_IRQ, &desc->flags);

}



void gpio_unlock_as_irq(struct gpio_chip *chip, unsigned int offset)

{

	return gpiod_unlock_as_irq(gpiochip_offset_to_desc(chip, offset));

}

EXPORT_SYMBOL_GPL(gpio_unlock_as_irq);



/* There's no value in making it easy to inline GPIO calls that may sleep.

 * Common examples include ones connected to I2C or SPI chips.
@@ -2091,6 +2172,7 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip) 
	unsigned		gpio = chip->base;

	struct gpio_desc	*gdesc = &chip->desc[0];

	int			is_out;

	int			is_irq;



	for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {

		if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
@@ -2098,12 +2180,14 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip) 


		gpiod_get_direction(gdesc);

		is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);

		seq_printf(s, " gpio-%-3d (%-20.20s) %s %s",

		is_irq = test_bit(FLAG_USED_AS_IRQ, &gdesc->flags);

		seq_printf(s, " gpio-%-3d (%-20.20s) %s %s %s",

			gpio, gdesc->label,

			is_out ? "out" : "in ",

			chip->get

				? (chip->get(chip, i) ? "hi" : "lo")

				: "?  ");

				: "?  ",

			is_irq ? "IRQ" : "   ");

		seq_printf(s, "\n");

	}

}

include/asm-generic/gpio.h

+3 −0
Original line number Diff line number Diff line
@@ -192,6 +192,9 @@ extern int __gpio_cansleep(unsigned gpio); 


extern int __gpio_to_irq(unsigned gpio);



extern int gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset);

extern void gpio_unlock_as_irq(struct gpio_chip *chip, unsigned int offset);



extern int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);

extern int gpio_request_array(const struct gpio *array, size_t num);

extern void gpio_free_array(const struct gpio *array, size_t num);

include/linux/gpio.h

+12 −0
Original line number Diff line number Diff line
@@ -204,6 +204,18 @@ static inline int gpio_to_irq(unsigned gpio) 
	return -EINVAL;

}



static inline int gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset)

{

	WARN_ON(1);

	return -EINVAL;

}



static inline void gpio_unlock_as_irq(struct gpio_chip *chip,

				      unsigned int offset)

{

	WARN_ON(1);

}



static inline int irq_to_gpio(unsigned irq)

{

	/* irq can never have been returned from gpio_to_irq() */