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Message-ID: <4B7127AC.9020600@petalogix.com>
Date: Tue, 09 Feb 2010 10:15:24 +0100
From: Michal Simek <michal.simek@...alogix.com>
To: Anton Vorontsov <avorontsov@...mvista.com>
CC: Grant Likely <grant.likely@...retlab.ca>,
David Brownell <dbrownell@...rs.sourceforge.net>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
David Miller <davem@...emloft.net>,
Michal Simek <monstr@...str.eu>, linuxppc-dev@...abs.org,
linux-kernel@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
microblaze-uclinux@...e.uq.edu.au
Subject: Re: [PATCH 3/3] of/gpio: Introduce of_put_gpio(), add ref counting
for OF GPIO chips
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 that of_get_gpio()'s returned GPIO number will be no longer valid, or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@...mvista.com>
> ---
> 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
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