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: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 4fc2860..1014cb5 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -60,6 +60,7 @@
#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 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);
@@ -163,6 +166,17 @@
}
/**
+ * 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
* use GPIO numbers for error messages and sysfs nodes
@@ -428,6 +442,7 @@
desc->flags &= ~GPIO_TRIGGER_MASK;
if (!gpio_flags) {
+ gpiod_unlock_as_irq(desc);
ret = 0;
goto free_id;
}
@@ -466,6 +481,12 @@
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 @@
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 @@
}
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 @@
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 @@
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");
}
}
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index bde6469..b309a5c 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -192,6 +192,9 @@
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);
diff --git a/include/linux/gpio.h b/include/linux/gpio.h
index 552e3f4..a06ec3e 100644
--- a/include/linux/gpio.h
+++ b/include/linux/gpio.h
@@ -204,6 +204,18 @@
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() */