gpio: dt: add gpio-export support

PATCH New Jean-Christophe PLAGNIOL-VILLARD 4 participants 15 messages Nov 21, 2012 – May 31, 2013

Subsystems (4)

Device tree bindings MIPS GPIO Generic include/asm header files

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Jean-Christophe PLAGNIOL-VILLARD

author

2012-11-21 10:12 UTC #0 lore raw

cover gpio: dt: add gpio-export support

HI,

This patch serie add the support of gpio-export to DT

This also extend to gpio_export with the possibility to specify a name for the gpio.
When you support different hardware you do not need to knwon which gpio is used at application level just you have it

based on next-20121115 tested on AT91 Animeo IP

gpiolib-of: ad gpio-export support (2012-11-19 20:36:03 +0800)

----------------------------------------------------------------
Jean-Christophe PLAGNIOL-VILLARD (2):
gpiolib: add gpio_export_with_name
gpiolib-of: ad gpio-export support

 Documentation/devicetree/bindings/gpio/gpio.txt |   60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 arch/mips/include/asm/mach-au1x00/gpio-au1000.h |    3 ++-
 arch/mips/include/asm/mach-au1x00/gpio-au1300.h |    3 ++-
 drivers/gpio/gpiolib-of.c                       |   61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpiolib.c                          |   12 +++++++-----
 include/asm-generic/gpio.h                      |    6 ++++--
 include/linux/gpio.h                            |   23 ++++++++++++++++++++++-
 7 files changed, 158 insertions(+), 10 deletions(-)

Best Regards,
J.

Jean-Christophe PLAGNIOL-VILLARD

author

2012-11-21 10:14 UTC #1 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

allow to specify a name to an exported gpio

Signed-off-by Jean-Christophe PLAGNIOL-VILLARD <[email protected]>

---
 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(-)

arch/mips/include/asm/mach-au1x00/gpio-au1000.h +2 -1

index 73853b5a..af4accb 100644
@@ -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;
 }

arch/mips/include/asm/mach-au1x00/gpio-au1300.h +2 -1

index fb9975c..fcd152e 100644
@@ -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;
 }

drivers/gpio/gpiolib.c +7 -5

index b667f76..2141165 100644
@@ -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 change

include/asm-generic/gpio.h +4 -2

index b6516f3..d04fc55 100644
@@ -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;
 }

include/linux/gpio.h +22 -1

index 7ba2762..6e01b8c 100644
@@ -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 */

Signature · 1 line

1.7.10.4

Jean-Christophe PLAGNIOL-VILLARD

author

2012-11-21 10:14 UTC #2 lore raw

PATCH 2/2 gpiolib-of: ad gpio-export support

This will allow to export gpios with or without names

Signed-off-by Jean-Christophe PLAGNIOL-VILLARD <[email protected]>

---
 Documentation/devicetree/bindings/gpio/gpio.txt |   60 ++++++++++++++++++++++
 drivers/gpio/gpiolib-of.c                       |   61 +++++++++++++++++++++++
 2 files changed, 121 insertions(+)

Documentation/devicetree/bindings/gpio/gpio.txt +60 -0

index a336287..c2a9024 100644
@@ -112,3 +112,63 @@ where,
 
 The pinctrl node must have "#gpio-range-cells" property to show number of
 arguments to pass with phandle from gpio controllers node.
+
+3) gpio-export
+--------------
+
+gpio-export will allow you to automatically export gpio
+
+required properties:
+- compatible: Should be "gpio-export"
+
+in each child node will reprensent a gpio or if no name is specified
+a list of gpio to export
+
+required properties:
+- gpios: gpio to export
+
+optional properties:
+ - gpio-export,name: export name
+ - gpio-export,output: to set the as output with default value
+ 		       if no present gpio as input
+ - pio-export,direction_may_change: boolean to allow the direction to be controllable
+
+Example:
+
+
+gpio_export {
+	compatible = "gpio-export";
+	#size-cells = <0>;
+
+	in {
+		gpio-export,name = "in";
+		gpios = <&pioC 20 0>;
+	};
+
+	out {
+		gpio-export,name = "out";
+		gpio-export,output = <1>;
+		gpio-export,direction_may_change;
+		gpios = <&pioC 21 0>;
+	};
+
+	in_out {
+		gpio-export,name = "in_out";
+		gpio-export,direction_may_change;
+		gpios = <&pioC 21 0>;
+	};
+
+	gpios_in {
+		gpios = <&pioB 0 0
+			 &pioB 3 0
+			 &pioC 4 0>;
+		gpio-export,direction_may_change;
+	};
+
+	gpios_out {
+		gpios = <&pioB 1 0
+			 &pioB 2 0
+			 &pioC 3 0>;
+		gpio-export,output = <1>;
+	};
+};

drivers/gpio/gpiolib-of.c +61 -0

70 lines not on this page · raw message

Signature · 1 line

1.7.10.4

Grant Likely

2012-11-26 13:59 UTC #3 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

In reply to Jean-Christophe PLAGNIOL-VILLARD

Quoted 3 lines · Jean-Christophe PLAGNIOL-VILLARD

allow to specify a name to an exported gpio
Signed-off-by Jean-Christophe PLAGNIOL-VILLARD <[email protected]>

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.

Quoted 160 lines

---
 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(-)

arch/mips/include/asm/mach-au1x00/gpio-au1000.h +2 -1

index 73853b5a..af4accb 100644
@@ -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;
 }

arch/mips/include/asm/mach-au1x00/gpio-au1300.h +2 -1

index fb9975c..fcd152e 100644
@@ -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;
 }

drivers/gpio/gpiolib.c +7 -5

index b667f76..2141165 100644
@@ -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 change

include/asm-generic/gpio.h +4 -2

index b6516f3..d04fc55 100644
@@ -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;
 }

include/linux/gpio.h +22 -1

index 7ba2762..6e01b8c 100644
@@ -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 */

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linux-arm-kernel at lists.infradead.org
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Signature · 2 lines

Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.

Jean-Christophe PLAGNIOL-VILLARD

author

2012-11-28 20:19 UTC #4 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

Quoted 10 lines · Grant Likely

Quoted 3 lines · Jean-Christophe PLAGNIOL-VILLARD
allow to specify a name to an exported gpio
Signed-off-by Jean-Christophe PLAGNIOL-VILLARD <[email protected]>
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.

I do agree on this and mention it on the ML multiple times but this an ABI and we can not change it anymore we need to support it

Quoted 7 lines

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.

the problem here is that I do not want the user space to become smart

I want the user space to known which gpio use for a specific feature as example you just want to read lack restistor to detect a hw features

you known the encoding it does not change cross hw but the pin to read do

So the idea is just to tell the user space use this pin to get your information

how to do you want to solve this?

This apply to other case:
- chip poweron/off
- reset
etc... all control by userspace

Best Regards,
J.

Quoted 167 lines

Quoted 160 lines

---
 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(-)

arch/mips/include/asm/mach-au1x00/gpio-au1000.h +2 -1

index 73853b5a..af4accb 100644
@@ -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;
 }

arch/mips/include/asm/mach-au1x00/gpio-au1300.h +2 -1

index fb9975c..fcd152e 100644
@@ -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;
 }

drivers/gpio/gpiolib.c +7 -5

index b667f76..2141165 100644
@@ -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 change

include/asm-generic/gpio.h +4 -2

index b6516f3..d04fc55 100644
@@ -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;
 }

include/linux/gpio.h +22 -1

index 7ba2762..6e01b8c 100644
@@ -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 */

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Signature · 2 lines

Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.

Jean-Christophe PLAGNIOL-VILLARD

author

2012-12-18 06:04 UTC #5 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

Quoted 30 lines · Jean-Christophe PLAGNIOL-VILLARD

Quoted 10 lines · Grant Likely
Quoted 3 lines · Jean-Christophe PLAGNIOL-VILLARD
allow to specify a name to an exported gpio
Signed-off-by Jean-Christophe PLAGNIOL-VILLARD <[email protected]>
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.
I do agree on this and mention it on the ML multiple times but this an ABI and we can not change it anymore we need to support it
Quoted 7 lines
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.
the problem here is that I do not want the user space to become smart
I want the user space to known which gpio use for a specific feature as example you just want to read lack restistor to detect a hw features
you known the encoding it does not change cross hw but the pin to read do
So the idea is just to tell the user space use this pin to get your information

Quoted 6 lines

how to do you want to solve this?
This apply to other case:
- chip poweron/off
- reset
etc... all control by userspace

ping

Quoted 174 lines

Best Regards,
J.

Quoted 159 lines

Quoted 156 lines

---
 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(-)

arch/mips/include/asm/mach-au1x00/gpio-au1000.h +2 -1

index 73853b5a..af4accb 100644
@@ -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;
 }

arch/mips/include/asm/mach-au1x00/gpio-au1300.h +2 -1

index fb9975c..fcd152e 100644
@@ -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;
 }

drivers/gpio/gpiolib.c +7 -5

index b667f76..2141165 100644
@@ -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 change

include/asm-generic/gpio.h +4 -2

index b6516f3..d04fc55 100644
@@ -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;
 }

include/linux/gpio.h +22 -1

index 7ba2762..6e01b8c 100644
@@ -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 */

Signature · 1 line

1.7.10.4

Quoted 8 lines

Quoted 4 lines
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel at lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Signature · 2 lines
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.

_______________________________________________
devicetree-discuss mailing list
devicetree-discuss at lists.ozlabs.org
https://lists.ozlabs.org/listinfo/devicetree-discuss

Grant Likely

2012-12-19 13:11 UTC #6 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

Quoted 31 lines · Jean-Christophe PLAGNIOL-VILLARD

Quoted 30 lines · Jean-Christophe PLAGNIOL-VILLARD
Quoted 10 lines · Grant Likely
Quoted 3 lines · Jean-Christophe PLAGNIOL-VILLARD
allow to specify a name to an exported gpio
Signed-off-by Jean-Christophe PLAGNIOL-VILLARD <[email protected]>
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.
I do agree on this and mention it on the ML multiple times but this an ABI and we can not change it anymore we need to support it
Quoted 7 lines
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.
the problem here is that I do not want the user space to become smart
I want the user space to known which gpio use for a specific feature as example you just want to read lack restistor to detect a hw features
you known the encoding it does not change cross hw but the pin to read do
So the idea is just to tell the user space use this pin to get your information

Quoted 8 lines

Quoted 6 lines
how to do you want to solve this?
This apply to other case:
- chip poweron/off
- reset
etc... all control by userspace
ping

I've already stated in other thread that I want to see a significantly better GPIO interface created. Something based on a char dev and can handle 'bursts' of gpio manipulations/reads. I'm not going to accept extensions to the sysfs interface.

Within that context I would consider named subsets of the same interface that pre-packages a set of related gpio pins.

That said, I'm not convinced that direct gpio access is the abstraction that you want. If it is an interface for, say, reading feature bits, then it probably does want to be an actual driver that reads the gpios/registers/adc/etc and returns the parsed status in a file. That's the only way to reliably get the abstraction from your example above.

Florian Vaussard

2013-05-30 09:19 UTC #7 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

In reply to Grant Likely

Hello Grant,

Quoted 12 lines · Grant Likely

Quoted 3 lines · Jean-Christophe PLAGNIOL-VILLARD
allow to specify a name to an exported gpio
Signed-off-by Jean-Christophe PLAGNIOL-VILLARD <[email protected]>
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.

Would it make sense to provide only the DT binding to export a GPIO, without changing the sysfs ABI? Even if work is progressing towards having gpio-controlled reset pins [1], some boards still need GPIOs to be exported to userspace for other functionalities.

Regards,

Florian

[1] http://article.gmane.org/gmane.linux.power-management.general/31364

Linus Walleij

2013-05-30 20:03 UTC #8 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

Quoted 3 lines · Florian Vaussard

Even if work is progressing towards
having gpio-controlled reset pins [1], some boards still need GPIOs to be exported to userspace for other functionalities.

Which are these?

When I have inquired I have heard all kind of horrible things:

- Userspace replicating drivers/leds/leds-gpio.c to turn on/off and even PWM (!) LEDs from userspace, when we have a standard sysfs interface for LEDs.

- Userspace replicating drivers/input/keyboard/gpio_keys[_polled].c to "just read this one button" instead of going through the Linux input subsystem like everyone else.

- Userspace replicating drivers/regulator/gpio-regulator.c to "turn on just this one voltage source".

All invalid reasons for using the sysfs ABI and trying to do the kernels work. All creating horrs for users and developers who now have to stash everything were trying to stach into the device tree (the above is all perfectly expressed with DT nodes) into their userspace app and then requiring their users to match a certain app to a certain board.

The only examples I've really come to accept considers using things like relays and switches on factory lines where the meaning (semantics) of the GPIOs can only be properly understood from the GUI in the userspace APP running that factory line. Or robotics. In both cases presumably RT processes.

Yours,
Linus Walleij

Florian Vaussard

2013-05-30 20:38 UTC #9 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

Hello Linus,

Quoted 9 lines · Linus Walleij

Quoted 3 lines · Florian Vaussard
Even if work is progressing towards
having gpio-controlled reset pins [1], some boards still need GPIOs to be exported to userspace for other functionalities.
Which are these?

Sorry, I should have been more precise.

Quoted 13 lines

When I have inquired I have heard all kind of horrible things:
- Userspace replicating drivers/leds/leds-gpio.c to turn on/off and even PWM (!) LEDs from userspace, when we have a standard sysfs interface for LEDs.
- Userspace replicating drivers/input/keyboard/gpio_keys[_polled].c to "just read this one button" instead of going through the Linux input subsystem like everyone else.
- Userspace replicating drivers/regulator/gpio-regulator.c to "turn on just this one voltage source".

Quoted 7 lines

All invalid reasons for using the sysfs ABI and trying to do the kernels work. All creating horrs for users and developers who now have to stash everything were trying to stach into the device tree (the above is all perfectly expressed with DT nodes) into their userspace app and then requiring their users to match a certain app to a certain board.

100% agree with you.

Quoted 6 lines

The only examples I've really come to accept considers using things like relays and switches on factory lines where the meaning (semantics) of the GPIOs can only be properly understood from the GUI in the userspace APP running that factory line. Or robotics. In both cases presumably RT processes.

Indeed, I work in a robotics lab :-) One of our board (mach-imx/ mx31moboard*.c) controls for example the multiplexing of two cameras sharing the same acquisition bus (I know, a bit hackish).
I developed a similar board with an OMAP3. Such control do not fit well in the above-mentioned cases, but we do not need RT processes.

Best regards,

Florian

Linus Walleij

2013-05-30 21:11 UTC #10 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

Quoted 5 lines · Florian Vaussard

Indeed, I work in a robotics lab :-) One of our board (mach-imx/ mx31moboard*.c) controls for example the multiplexing of two cameras sharing the same acquisition bus (I know, a bit hackish).
I developed a similar board with an OMAP3. Such control do not fit well in the above-mentioned cases, but we do not need RT processes.

It does seem to fit well with V4L and/or the media controller framework though, or is this one of those "oh, we don't really like to use V4L so we have this special hack instead" things?

Yours,
Linus Walleij

Florian Vaussard

2013-05-31 08:17 UTC #11 lore raw

PATCH 1/2 gpiolib: add gpio_export_with_name

Hello Linus,

Quoted 9 lines · Linus Walleij

Quoted 5 lines · Florian Vaussard
Indeed, I work in a robotics lab :-) One of our board (mach-imx/ mx31moboard*.c) controls for example the multiplexing of two cameras sharing the same acquisition bus (I know, a bit hackish).
I developed a similar board with an OMAP3. Such control do not fit well in the above-mentioned cases, but we do not need RT processes.

Quoted 4 lines

It does seem to fit well with V4L and/or the media controller framework though, or is this one of those "oh, we don't really like to use V4L so we have this special hack instead" things?

Sorry, I was not aware of this mux capability inside V4L. Thank you. So we can live without gpio-export for most of our hardware.

Regards,

Florian

Linus Walleij

2012-11-21 14:43 UTC #12 lore raw

cover gpio: dt: add gpio-export support

In reply to Jean-Christophe PLAGNIOL-VILLARD

Quoted 4 lines · Jean-Christophe PLAGNIOL-VILLARD

HI,
This patch serie add the support of gpio-export to DT

Quoted 8 lines

This also extend to gpio_export with the possibility to specify a name for the gpio.
When you support different hardware you do not need to knwon which gpio is used at application level just you have it
based on next-20121115 tested on AT91 Animeo IP
gpiolib-of: ad gpio-export support (2012-11-19 20:36:03 +0800)

OK so this is definately Grant territory, I'm just a novice in DT land... Grant can you look at this?

Yours,
Linus Walleij

Jean-Christophe PLAGNIOL-VILLARD

author

2012-11-24 18:48 UTC #13 lore raw

cover gpio: dt: add gpio-export support

Quoted 12 lines · Linus Walleij

Quoted 9 lines · Jean-Christophe PLAGNIOL-VILLARD
HI,
This patch serie add the support of gpio-export to DT
This also extend to gpio_export with the possibility to specify a name for the gpio.
When you support different hardware you do not need to knwon which gpio is used at application level just you have it

Quoted 6 lines

Quoted 3 lines
based on next-20121115 tested on AT91 Animeo IP
gpiolib-of: ad gpio-export support (2012-11-19 20:36:03 +0800)
OK so this is definately Grant territory, I'm just a novice in DT land... Grant can you look at this?

Grant any comment?

Best Regards,
J.

Linus Walleij

2012-12-01 16:56 UTC #14 lore raw

cover gpio: dt: add gpio-export support

Quoted 13 lines · Jean-Christophe PLAGNIOL-VILLARD

Quoted 12 lines · Linus Walleij
Quoted 9 lines · Jean-Christophe PLAGNIOL-VILLARD
HI,
This patch serie add the support of gpio-export to DT
This also extend to gpio_export with the possibility to specify a name for the gpio.
When you support different hardware you do not need to knwon which gpio is used at application level just you have it

Quoted 7 lines

Quoted 6 lines
Quoted 3 lines
based on next-20121115 tested on AT91 Animeo IP
gpiolib-of: ad gpio-export support (2012-11-19 20:36:03 +0800)
OK so this is definately Grant territory, I'm just a novice in DT land... Grant can you look at this?
Grant any comment?

Yeah, ping on Grant :-)

He did come back online last week but will need time to catch up.

Yours,
Linus Walleij