[PATCH v4 4/6] gpio: introduce lock mechanism for gpiochip_find
Dong Aisheng
b29396 at freescale.com
Fri May 25 09:36:18 EDT 2012
From: Dong Aisheng <dong.aisheng at linaro.org>
The module lock will be automatically claimed for gpiochip_find function
in case the gpio module is removed during the using of gpiochip instance.
Users are responsible to call gpiochip_put to release the lock after
the using.
Signed-off-by: Dong Aisheng <dong.aisheng at linaro.org>
---
drivers/gpio/gpiolib-of.c | 5 ++++-
drivers/gpio/gpiolib.c | 17 +++++++++++++++++
include/asm-generic/gpio.h | 2 +-
3 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index b8010a9..d521452 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -63,6 +63,7 @@ int of_get_named_gpio_flags(struct device_node *np, const char *propname,
int index, enum of_gpio_flags *flags)
{
struct gg_data gg_data = { .flags = flags, .out_gpio = -ENODEV };
+ struct gpio_chip *chip;
int ret;
/* .of_xlate might decide to not fill in the flags, so clear it. */
@@ -76,7 +77,9 @@ int of_get_named_gpio_flags(struct device_node *np, const char *propname,
return -EINVAL;
}
- gpiochip_find(&gg_data, of_gpiochip_find_and_xlate);
+ chip = gpiochip_find(&gg_data, of_gpiochip_find_and_xlate);
+ if (chip)
+ gpiochip_put(chip);
of_node_put(gg_data.gpiospec.np);
pr_debug("%s exited with status %d\n", __func__, ret);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 120b2a0..6453d43 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1144,6 +1144,18 @@ int gpiochip_remove(struct gpio_chip *chip)
EXPORT_SYMBOL_GPL(gpiochip_remove);
/**
+ * gpiochip_put() - release a gpio_chip
+ * @chip: the chip to release
+ */
+inline void gpiochip_put(struct gpio_chip *chip)
+{
+ BUG_ON(!chip);
+
+ module_put(chip->owner);
+}
+EXPORT_SYMBOL_GPL(gpiochip_put);
+
+/**
* gpiochip_find() - iterator for locating a specific gpio_chip
* @data: data to pass to match function
* @callback: Callback function to check gpio_chip
@@ -1153,6 +1165,9 @@ EXPORT_SYMBOL_GPL(gpiochip_remove);
* 0 if the device doesn't match and non-zero if it does. If the callback is
* non-zero, this function will return to the caller and not iterate over any
* more gpio_chips.
+ *
+ * Note the gpio_chip is returned with the module locked, users are responsible
+ * to release the lock with gpiochip_put(chip) after using it.
*/
struct gpio_chip *gpiochip_find(void *data,
int (*match)(struct gpio_chip *chip,
@@ -1169,6 +1184,8 @@ struct gpio_chip *gpiochip_find(void *data,
if (match(gpio_desc[i].chip, data)) {
chip = gpio_desc[i].chip;
+ if (!try_module_get(chip->owner))
+ chip = NULL;
break;
}
}
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 365ea09..af372be 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -145,7 +145,7 @@ extern int __must_check gpiochip_remove(struct gpio_chip *chip);
extern struct gpio_chip *gpiochip_find(void *data,
int (*match)(struct gpio_chip *chip,
void *data));
-
+extern void gpiochip_put(struct gpio_chip *chip);
/* Always use the library code for GPIO management calls,
* or when sleeping may be involved.
--
1.7.0.4
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