of/gpio: Introduce of_put_gpio(), add ref counting for OF GPIO chips
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From: Michal Simek on 9 Feb 2010 04:20 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 that of_get_gpio()'s returned GPIO number will be no longer valid, or 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(a)ru.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Michal Simek on 9 Feb 2010 04:30 Michal Simek wrote: > 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. I see where the problem is. I applied Andrews patch too that's why I am getting the fault above. Anyway will be good to fix it. Will test gpio and let you know. Michal > > 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(a)ru.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Anton Vorontsov on 9 Feb 2010 14:20 On Tue, Feb 09, 2010 at 10:28:15AM -0700, Grant Likely wrote: [...] > Rather than having a lock at the device tree data pointer level which > mixes usage with potentially many other drivers; wouldn't it make more > sense to use a mutex at the of_gc subsystem context? I don't think so. of_gc = np->data; lock(of_gc); (or lock(devtree)) <do something with of_gc> doesn't provide us what we need, i.e. it doesn't guarantee that np->data (of_gc) is still alive. And here: lock(np->data); (or lock(devtree)) of_gc = np->data; lock(of_gc); <do something with of_gc> The second lock becomes useless (unless you also refcount np->data usage and can drop the devtree/np->data lock, and grab some other kind of lock, e.g. mutex, but this is silly). Thanks, -- Anton Vorontsov email: cbouatmailru(a)gmail.com irc://irc.freenode.net/bd2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Anton Vorontsov on 15 Feb 2010 16:00
On Mon, Feb 15, 2010 at 12:49:56PM -0700, Grant Likely wrote: [...] > Okay, I'm convinced now. The model is wrong. struct of_gc does need > to be a member of struct gpio_chip and conditionally compiled against > CONFIG_OF_GPIO. This locking requirement is just too plain ugly, And how would you implement of_get_gpio(np, index) then? You don't have 'struct gpio_chip' in of_get_gpio(), so you can't get of_gc out of it. It's possible to lookup all GPIOs (gpio[0..ARCH_NR_GPIOS]) matching on chip->dev->archdata.node == np, but you're just moving this stuff into gpiolib, where you'll have to grab global gpio_lock instead of devtree lock. And just as with np->data_lock or global devtree lock, you'll have to grab gpio_lock in of_gpio_put(), of_gpio_chip_register and of_gpio_chip_unregister(). See? Your suggestion doesn't make things better or simpler, instead it turns the OF GPIO inside out, exposing arch details to the generic code. There is really no excuse for the arch-specific (OF) stuff being in the generic code. Not in the irq subsystem, not in the gpio subsystem. My implementation actually proves that. > and > dereferencing the np->data pointer in this way is dangerous > (what if > something that is not struct of_gc is stored there). Not possible with the safe np->data accessors. -- Anton Vorontsov email: cbouatmailru(a)gmail.com irc://irc.freenode.net/bd2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |