Re: [PATCH 3/3] of/gpio: Introduce of_put_gpio(), add ref countingfor OF GPIO chips
From: Michal Simek
Date: Tue Feb 09 2010 - 04:18:19 EST
Anton Vorontsov wrote:
OF GPIO infrastructure is using dynamic GPIO bases, so it is possible
that of_get_gpio()'s returned GPIO number will be no longer valid, or
worse, it may point to an unexpected GPIO controller.
I am not able to apply this last patch.
$ git-am < \[PATCH\ 3_3\]\ of_gpio\:\ Introduce\ of_put_gpio\(\)\,\ add\
ref\ counting\ for\ OF\ GPIO\ chips.eml
Applying of/gpio: Introduce of_put_gpio(), add ref counting for OF GPIO
chips
error: patch failed: drivers/of/gpio.c:254
error: drivers/of/gpio.c: patch does not apply
Patch failed at 0001.
When you have resolved this problem run "git-am --resolved".
If you would prefer to skip this patch, instead run "git-am --skip".
Below is my git-log which patches I applied.
Please fix it.
Thanks,
Michal
99d5baaa53562252a896080bf426b4ae71a5e55f of: Introduce safe accessors
for node->data
df6d71af9c0691716ad8a368609a7e26a8dfdaa0 of platforms: Move common
static initialization to of_node_init()
566969302a9dd70ce8a07c978bd08804ee73d0d6 powerpc/mcu_mpc8349emitx:
Remove OF GPIO handling stuff
816932ea74919867c1f899758ea4cdd138145453 of/gpio: Implement GPIOLIB
notifier hooks
3ea035a9e0f446b2b9cd9bacf73395a0c80ae3e9 of/gpio: Implement GPIOLIB
notifier hooks
b7b96a9ee215c800476d002b06a338c4499f3813 of/gpio: Add support for
two-stage registration for the of_gpio_chips
15678cc192c03a2b1bbb36da18ff2a3fe2d78897 gpiolib: Introduce chip
addition/removal notifier
deb0c98c7f6035d47a247e548384517a955314a5 Merge branch 'for-2.6.33' of
git://linux-nfs.org/~bfields/linux
This scenario is possible:
driver A: driver B: driver C:
--------- --------- ---------
gpiochip_add()
gpio = of_get_gpio()
gpiochip_remove()
gpiochip_add()
gpio_request(gpio);
gpio_set_value(gpio);
That is, driver A assumes that it is working with GPIO from driver B,
but in practice it may disappear and driver C will take its GPIO base
number, so it will provide the same GPIO numbers.
With this patch that situation is no longer possible. Though drivers
will need to learn to put GPIOs back, so that GPIO controllers could
be removed.
Signed-off-by: Anton Vorontsov <avorontsov@xxxxxxxxxxxxx>
---
drivers/of/gpio.c | 82 ++++++++++++++++++++++++++++++++++++++++-------
include/linux/of_gpio.h | 5 +++
2 files changed, 75 insertions(+), 12 deletions(-)
diff --git a/drivers/of/gpio.c b/drivers/of/gpio.c
index 9d8df77..e94c5c8 100644
--- a/drivers/of/gpio.c
+++ b/drivers/of/gpio.c
@@ -28,6 +28,8 @@
* Returns GPIO number to use with Linux generic GPIO API, or one of the errno
* value on the error condition. If @flags is not NULL the function also fills
* in flags for the GPIO.
+ *
+ * Remeber to put the GPIO back using of_put_gpio() call.
*/
int of_get_gpio_flags(struct device_node *np, int index,
enum of_gpio_flags *flags)
@@ -46,6 +48,8 @@ int of_get_gpio_flags(struct device_node *np, int index,
goto err0;
}
+ spin_lock(&gc->data_lock);
+
of_gc = gc->data;
if (!of_gc) {
pr_debug("%s: gpio controller %s isn't registered\n",
@@ -72,15 +76,62 @@ int of_get_gpio_flags(struct device_node *np, int index,
goto err1;
ret += of_gc->chip->base;
+
+ if (!try_module_get(of_gc->chip->owner)) {
+ ret = -EINVAL;
+ goto err1;
+ }
+
+ of_gc->refcnt++;
err1:
+ spin_unlock(&gc->data_lock);
+
of_node_put(gc);
err0:
pr_debug("%s exited with status %d\n", __func__, ret);
+
return ret;
}
EXPORT_SYMBOL(of_get_gpio_flags);
/**
+ * of_put_gpio - Put a GPIO back to the OF subsystem
+ * @np: device node of the GPIO owner
+ * @index: index of the GPIO
+ */
+static inline void of_put_gpio(struct device_node *np, int index)
+{
+ int ret;
+ struct device_node *gc;
+ struct of_gpio_chip *of_gc;
+
+ ret = of_parse_phandles_with_args(np, "gpios", "#gpio-cells", index,
+ &gc, NULL);
+ if (ret) {
+ pr_debug("%s: can't parse gpios property\n", __func__);
+ return;
+ }
+
+ spin_lock(&gc->data_lock);
+
+ of_gc = gc->data;
+ if (!of_gc) {
+ pr_debug("%s: gpio controller %s isn't registered\n",
+ np->full_name, gc->full_name);
+ goto err;
+ }
+
+ if (of_gc->refcnt)
+ of_gc->refcnt--;
+ else
+ WARN_ON(1);
+
+ module_put(of_gc->chip->owner);
+err:
+ spin_unlock(&gc->data_lock);
+}
+
+/**
* of_gpio_count - Count GPIOs for a device
* @np: device node to count GPIOs for
*
@@ -254,11 +305,7 @@ static int of_gpiochip_register_simple(struct gpio_chip *chip,
struct device_node *np)
{
struct of_gpio_chip *of_gc;
-
- if (np->data) {
- WARN_ON(1);
- return -EBUSY;
- }
+ int ret;
of_gc = kzalloc(sizeof(*of_gc), GFP_KERNEL);
if (!of_gc)
@@ -267,10 +314,12 @@ static int of_gpiochip_register_simple(struct gpio_chip *chip,
of_gc->gpio_cells = 2;
of_gc->xlate = of_gpio_simple_xlate;
of_gc->chip = chip;
- np->data = of_gc;
- of_node_get(np);
- return 0;
+ ret = of_node_set_data(np, of_gc);
+ if (ret)
+ kfree(of_gc);
+
+ return ret;
}
EXPORT_SYMBOL(of_gpiochip_register_simple);
@@ -286,17 +335,26 @@ static int of_gpiochip_unregister(struct gpio_chip *chip,
struct device_node *np)
{
struct of_gpio_chip *of_gc = np->data;
+ int ret = 0;
if (!of_gc || of_gc->chip != chip) {
WARN_ON(1);
return -EINVAL;
}
- np->data = NULL;
- kfree(of_gc);
- of_node_put(np);
+ spin_lock(&np->data_lock);
- return 0;
+ if (of_gc->refcnt)
+ ret = -EBUSY;
+ else
+ of_node_release_data_unlocked(np);
+
+ spin_unlock(&np->data_lock);
+
+ if (!ret)
+ kfree(of_gc);
+
+ return ret;
}
static int of_gpio_notify(struct notifier_block *nb, unsigned long msg,
diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h
index c74cb37..aca7ab1 100644
--- a/include/linux/of_gpio.h
+++ b/include/linux/of_gpio.h
@@ -38,6 +38,7 @@ enum of_gpio_flags {
struct of_gpio_chip {
struct gpio_chip gc; /* legacy, don't use for a new code */
struct gpio_chip *chip;
+ unsigned int refcnt;
int gpio_cells;
int (*xlate)(struct of_gpio_chip *of_gc, struct device_node *np,
const void *gpio_spec, enum of_gpio_flags *flags);
@@ -83,6 +84,8 @@ static inline int of_get_gpio_flags(struct device_node *np, int index,
return -ENOSYS;
}
+static inline void of_put_gpio(struct device_node *np, int index) {}
+
static inline unsigned int of_gpio_count(struct device_node *np)
{
return 0;
@@ -97,6 +100,8 @@ static inline unsigned int of_gpio_count(struct device_node *np)
*
* Returns GPIO number to use with Linux generic GPIO API, or one of the errno
* value on the error condition.
+ *
+ * Remeber to put the GPIO back using of_put_gpio() call.
*/
static inline int of_get_gpio(struct device_node *np, int index)
{
--
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/