[PATCH 1/2] gpiolib: add gpio_export_with_name
From: Grant Likely <hidden>
Date: 2012-11-26 13:59:11
Also in:
linux-devicetree
Possibly related (same subject, not in this thread)
- 2013-05-31 · Re: [PATCH 1/2] gpiolib: add gpio_export_with_name · Florian Vaussard <hidden>
- 2013-05-30 · Re: [PATCH 1/2] gpiolib: add gpio_export_with_name · Linus Walleij <hidden>
- 2013-05-30 · Re: [PATCH 1/2] gpiolib: add gpio_export_with_name · Florian Vaussard <hidden>
- 2013-05-30 · Re: [PATCH 1/2] gpiolib: add gpio_export_with_name · Linus Walleij <hidden>
- 2012-12-19 · Re: [PATCH 1/2] gpiolib: add gpio_export_with_name · Grant Likely <hidden>
On Wed, 21 Nov 2012 11:14:08 +0100, Jean-Christophe PLAGNIOL-VILLARD [off-list ref] wrote:
allow to specify a name to an exported gpio Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <redacted>
The gpio sysfs ABI is already horrible, racy, and unsafe. Really, we need a proper chrdev interface for controlling gpios. Sysfs is fine for poking around and experimenting, but we cannot provide any fine grained access control, locking or faster IO with the one-file-per-gpio sysfs model. So, no, I don't think this is a good idea to extend gpiolib in this way. However, I would be okay with making gpiochips first-class kobjects or struct devices that appear as a child of the gpio controller device so that userspace could interrogate the device tree node associated with the device. g.
quoted hunk ↗ jump to hunk
--- arch/mips/include/asm/mach-au1x00/gpio-au1000.h | 3 ++- arch/mips/include/asm/mach-au1x00/gpio-au1300.h | 3 ++- drivers/gpio/gpiolib.c | 12 +++++++----- include/asm-generic/gpio.h | 6 ++++-- include/linux/gpio.h | 23 ++++++++++++++++++++++- 5 files changed, 37 insertions(+), 10 deletions(-)diff --git a/arch/mips/include/asm/mach-au1x00/gpio-au1000.h b/arch/mips/include/asm/mach-au1x00/gpio-au1000.h index 73853b5a..af4accb 100644 --- a/arch/mips/include/asm/mach-au1x00/gpio-au1000.h +++ b/arch/mips/include/asm/mach-au1x00/gpio-au1000.h@@ -633,7 +633,8 @@ static inline int gpio_set_debounce(unsigned gpio, unsigned debounce) return -ENOSYS; } -static inline int gpio_export(unsigned gpio, bool direction_may_change) +static inline int gpio_export_with_name(unsigned gpio, + bool direction_may_change, const char *name) { return -ENOSYS; }diff --git a/arch/mips/include/asm/mach-au1x00/gpio-au1300.h b/arch/mips/include/asm/mach-au1x00/gpio-au1300.h index fb9975c..fcd152e 100644 --- a/arch/mips/include/asm/mach-au1x00/gpio-au1300.h +++ b/arch/mips/include/asm/mach-au1x00/gpio-au1300.h@@ -234,7 +234,8 @@ static inline void gpio_unexport(unsigned gpio) { } -static inline int gpio_export(unsigned gpio, bool direction_may_change) +static inline int gpio_export_with_name(unsigned gpio, + bool direction_may_change, const char *name) { return -ENOSYS; }diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index b667f76..2141165 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c@@ -714,9 +714,10 @@ static struct class gpio_class = { /** - * gpio_export - export a GPIO through sysfs + * gpio_export_with_name - export a GPIO through sysfs * @gpio: gpio to make available, already requested * @direction_may_change: true if userspace may change gpio direction + * @name: gpio name * Context: arch_initcall or later * * When drivers want to make a GPIO accessible to userspace after they@@ -728,7 +729,7 @@ static struct class gpio_class = { * * Returns zero on success, else an error. */ -int gpio_export(unsigned gpio, bool direction_may_change) +int gpio_export_with_name(unsigned gpio, bool direction_may_change, const char *name) { unsigned long flags; struct gpio_desc *desc;@@ -766,7 +767,9 @@ int gpio_export(unsigned gpio, bool direction_may_change) direction_may_change = false; spin_unlock_irqrestore(&gpio_lock, flags); - if (desc->chip->names && desc->chip->names[gpio - desc->chip->base]) + if (name) + ioname = name; + else if (desc->chip->names && desc->chip->names[gpio - desc->chip->base]) ioname = desc->chip->names[gpio - desc->chip->base]; dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),@@ -804,7 +807,7 @@ fail_unlock: pr_debug("%s: gpio%d status %d\n", __func__, gpio, status); return status; } -EXPORT_SYMBOL_GPL(gpio_export); +EXPORT_SYMBOL_GPL(gpio_export_with_name); static int match_export(struct device *dev, void *data) {@@ -856,7 +859,6 @@ done: } EXPORT_SYMBOL_GPL(gpio_export_link); - /** * gpio_sysfs_set_active_low - set the polarity of gpio sysfs value * @gpio: gpio to changediff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h index b6516f3..d04fc55 100644 --- a/include/asm-generic/gpio.h +++ b/include/asm-generic/gpio.h@@ -204,7 +204,8 @@ void devm_gpio_free(struct device *dev, unsigned int gpio); * A sysfs interface can be exported by individual drivers if they want, * but more typically is configured entirely from userspace. */ -extern int gpio_export(unsigned gpio, bool direction_may_change); +extern int gpio_export_with_name(unsigned gpio, bool direction_may_change, + const char *name); extern int gpio_export_link(struct device *dev, const char *name, unsigned gpio); extern int gpio_sysfs_set_active_low(unsigned gpio, int value);@@ -249,7 +250,8 @@ struct device; /* sysfs support is only available with gpiolib, where it's optional */ -static inline int gpio_export(unsigned gpio, bool direction_may_change) +static inline int gpio_export_with_name(unsigned gpio, + bool direction_may_change, const char *name) { return -ENOSYS; }diff --git a/include/linux/gpio.h b/include/linux/gpio.h index 7ba2762..6e01b8c 100644 --- a/include/linux/gpio.h +++ b/include/linux/gpio.h@@ -189,7 +189,8 @@ static inline void gpio_set_value_cansleep(unsigned gpio, int value) WARN_ON(1); } -static inline int gpio_export(unsigned gpio, bool direction_may_change) +static inline int gpio_export_with_name(unsigned gpio, + bool direction_may_change, const char *name) { /* GPIO can never have been requested or set as {in,out}put */ WARN_ON(1);@@ -247,4 +248,24 @@ gpiochip_remove_pin_ranges(struct gpio_chip *chip) #endif /* ! CONFIG_GENERIC_GPIO */ +/** + * gpio_export - export a GPIO through sysfs + * @gpio: gpio to make available, already requested + * @direction_may_change: true if userspace may change gpio direction + * Context: arch_initcall or later + * + * When drivers want to make a GPIO accessible to userspace after they + * have requested it -- perhaps while debugging, or as part of their + * public interface -- they may use this routine. If the GPIO can + * change direction (some can't) and the caller allows it, userspace + * will see "direction" sysfs attribute which may be used to change + * the gpio's direction. A "value" attribute will always be provided. + * + * Returns zero on success, else an error. + */ +static inline int gpio_export(unsigned gpio,bool direction_may_change) +{ + return gpio_export_with_name(gpio, direction_may_change, NULL); +} + #endif /* __LINUX_GPIO_H */-- 1.7.10.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel at lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
-- Grant Likely, B.Sc, P.Eng. Secret Lab Technologies, Ltd.