[Patch v6 0/2] gpio: add GPIO hogging mechanism

[Patch v6 0/2] gpio: add GPIO hogging mechanism

[Benoit Parrot]

This patch set re-introduces the gpio hogging concept first 
presented by Boris Brezillion.
This patch set provides a way to initially configure specific GPIO
when the GPIO controller is probed.

The actual DT scanning to collect the GPIO specific data is performed
as part of of_gpiochip_add().

The purpose of this is to allow specific GPIOs to be configured
without any driver specific code.
This is particularly useful because board design are getting
increasingly complex and given SoC pins can now have more
than 10 mux values a lot of connections are now dependent on
external IO muxes to switch various modes.

Specific drivers should not necessarily need to be aware of
what accounts to a specific board implementation. This board level
"description" should be best kept as part of the dts file.

Changes since v5:
 * Addressed review comment from Linus Walleij
 * Replace "state" property back with separate boolean properties
 * Renamed helper function
 * Refactored pr_* calls to remove "__func__"

Changes since v4:
 * Addressed review comments from Alexandre Courbot

Changes since v3:
 * Relocated the non-DT "hog" function to gpiolib.c.
 * Rename some of the function to be clearer and remove _ prefixes.
 * Replace the gpiod_request/gpiod_put usage with
   gpiochip_request_own_desc/free_own_desc version instead.
 * Refactor some of the logic to better handle error condition/reporting
 * Renamed the "direction" DT properties to "state".

Changes since v2:
 * Refactor the gpio-hog mechanism to split the DT related action
   from the actual "hogging" operation.
 * This allows non-DT providers to implement hogs as well.
 * Added FLAG_IS_HOGGED to mark hogged gpio and make gpiochip removal
   able to release hogged gpio.
 * Similarly to the hogging, the cleanup is performed as part of
   of_gpiochip_remove

Changes since v1:
 * Split the devicetree bindings documentation in its own patch.
 * Refactor the gpio-hog mechanism as private functions meant to
   be to invoked from of_gpiochip_add().


Benoit Parrot (2):
  gpio: add GPIO hogging mechanism
  gpio: Document GPIO hogging mechanism

 Documentation/devicetree/bindings/gpio/gpio.txt |  30 ++++++
 drivers/gpio/gpiolib-of.c                       | 111 +++++++++++++++++++++
 drivers/gpio/gpiolib.c                          | 124 ++++++++++++++++++++----
 drivers/gpio/gpiolib.h                          |   3 +
 4 files changed, 249 insertions(+), 19 deletions(-)

-- 
1.8.5.1

[Patch v6 0/2] gpio: add GPIO hogging mechanism

[Benoit Parrot]

This patch set re-introduces the gpio hogging concept first 
presented by Boris Brezillion.
This patch set provides a way to initially configure specific GPIO
when the GPIO controller is probed.

The actual DT scanning to collect the GPIO specific data is performed
as part of of_gpiochip_add().

The purpose of this is to allow specific GPIOs to be configured
without any driver specific code.
This is particularly useful because board design are getting
increasingly complex and given SoC pins can now have more
than 10 mux values a lot of connections are now dependent on
external IO muxes to switch various modes.

Specific drivers should not necessarily need to be aware of
what accounts to a specific board implementation. This board level
"description" should be best kept as part of the dts file.

Changes since v5:
 * Addressed review comment from Linus Walleij
 * Replace "state" property back with separate boolean properties
 * Renamed helper function
 * Refactored pr_* calls to remove "__func__"

Changes since v4:
 * Addressed review comments from Alexandre Courbot

Changes since v3:
 * Relocated the non-DT "hog" function to gpiolib.c.
 * Rename some of the function to be clearer and remove _ prefixes.
 * Replace the gpiod_request/gpiod_put usage with
   gpiochip_request_own_desc/free_own_desc version instead.
 * Refactor some of the logic to better handle error condition/reporting
 * Renamed the "direction" DT properties to "state".

Changes since v2:
 * Refactor the gpio-hog mechanism to split the DT related action
   from the actual "hogging" operation.
 * This allows non-DT providers to implement hogs as well.
 * Added FLAG_IS_HOGGED to mark hogged gpio and make gpiochip removal
   able to release hogged gpio.
 * Similarly to the hogging, the cleanup is performed as part of
   of_gpiochip_remove

Changes since v1:
 * Split the devicetree bindings documentation in its own patch.
 * Refactor the gpio-hog mechanism as private functions meant to
   be to invoked from of_gpiochip_add().


Benoit Parrot (2):
  gpio: add GPIO hogging mechanism
  gpio: Document GPIO hogging mechanism

 Documentation/devicetree/bindings/gpio/gpio.txt |  30 ++++++
 drivers/gpio/gpiolib-of.c                       | 111 +++++++++++++++++++++
 drivers/gpio/gpiolib.c                          | 124 ++++++++++++++++++++----
 drivers/gpio/gpiolib.h                          |   3 +
 4 files changed, 249 insertions(+), 19 deletions(-)

-- 
1.8.5.1

[Patch v6 1/2] gpio: add GPIO hogging mechanism

[Benoit Parrot]

Based on Boris Brezillion's work this is a reworked patch
of his initial GPIO hogging mechanism.
This patch provides a way to initially configure specific GPIO
when the GPIO controller is probed.

The actual DT scanning to collect the GPIO specific data is performed
as part of gpiochip_add().

The purpose of this is to allow specific GPIOs to be configured
without any driver specific code.
This is particularly useful because board design are getting
increasingly complex and given SoC pins can now have more
than 10 mux values, a lot of connections are now dependent on
external IO muxes to switch various modes.

Specific drivers should not necessarily need to be aware of
what accounts to a specific board implementation. This board level
"description" should be best kept as part of the dts file.

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/gpio/gpiolib-of.c | 111 +++++++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpiolib.c    | 124 +++++++++++++++++++++++++++++++++++++++-------
 drivers/gpio/gpiolib.h    |   3 ++
 3 files changed, 219 insertions(+), 19 deletions(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 08261f2..cfb50b4 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -22,6 +22,7 @@
 #include <linux/of_gpio.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/slab.h>
+#include <linux/gpio/machine.h>
 
 #include "gpiolib.h"
 
@@ -117,6 +118,114 @@ int of_get_named_gpio_flags(struct device_node *np, const char *list_name,
 EXPORT_SYMBOL(of_get_named_gpio_flags);
 
 /**
+ * of_get_gpio_hog() - Get a GPIO hog descriptor, names and flags for GPIO API
+ * @np:		device node to get GPIO from
+ * @name:	GPIO line name
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ *
+ * Returns GPIO descriptor to use with Linux GPIO API, or one of the errno
+ * value on the error condition.
+ */
+static struct gpio_desc *of_get_gpio_hog(struct device_node *np,
+				  const char **name,
+				  enum gpio_lookup_flags *lflags,
+				  enum gpiod_flags *dflags)
+{
+	struct device_node *chip_np;
+	enum of_gpio_flags xlate_flags;
+	struct gpio_desc *desc;
+	struct gg_data gg_data = {
+		.flags = &xlate_flags,
+	};
+	u32 tmp;
+	int i, ret;
+
+	chip_np = np->parent;
+	if (!chip_np)
+		return ERR_PTR(-EINVAL);
+
+	xlate_flags = 0;
+	*lflags = 0;
+	*dflags = 0;
+
+	ret = of_property_read_u32(chip_np, "#gpio-cells", &tmp);
+	if (ret)
+		return ERR_PTR(ret);
+
+	if (tmp > MAX_PHANDLE_ARGS)
+		return ERR_PTR(-EINVAL);
+
+	gg_data.gpiospec.args_count = tmp;
+	gg_data.gpiospec.np = chip_np;
+	for (i = 0; i < tmp; i++) {
+		ret = of_property_read_u32_index(np, "gpios", i,
+					   &gg_data.gpiospec.args[i]);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
+	gpiochip_find(&gg_data, of_gpiochip_find_and_xlate);
+	if (!gg_data.out_gpio) {
+		if (np->parent == np)
+			return ERR_PTR(-ENXIO);
+		else
+			return ERR_PTR(-EINVAL);
+	}
+
+	if (xlate_flags & OF_GPIO_ACTIVE_LOW)
+		*lflags |= GPIO_ACTIVE_LOW;
+
+	if (of_property_read_bool(np, "input"))
+		*dflags |= GPIOD_IN;
+	else if (of_property_read_bool(np, "output-low"))
+		*dflags |= GPIOD_OUT_LOW;
+	else if (of_property_read_bool(np, "output-high"))
+		*dflags |= GPIOD_OUT_HIGH;
+	else {
+		pr_warn("GPIO line %d (%s): no hogging state specified, bailing out\n",
+			desc_to_gpio(gg_data.out_gpio), np->name);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (name && of_property_read_string(np, "line-name", name))
+		*name = np->name;
+
+	desc = gg_data.out_gpio;
+
+	return desc;
+}
+
+/**
+ * of_gpiochip_scan_hogs - Scan gpio-controller and apply GPIO hog as requested
+ * @chip:	gpio chip to act on
+ *
+ * This is only used by of_gpiochip_add to request/set GPIO initial
+ * configuration.
+ */
+static void of_gpiochip_scan_hogs(struct gpio_chip *chip)
+{
+	struct gpio_desc *desc = NULL;
+	struct device_node *np;
+	const char *name;
+	enum gpio_lookup_flags lflags;
+	enum gpiod_flags dflags;
+
+	for_each_child_of_node(chip->of_node, np) {
+		if (!of_property_read_bool(np, "gpio-hog"))
+			continue;
+
+		desc = of_get_gpio_hog(np, &name, &lflags, &dflags);
+		if (IS_ERR(desc))
+			continue;
+
+		if (gpiod_hog(desc, name, lflags, dflags))
+			continue;
+	}
+}
+
+/**
  * of_gpio_simple_xlate - translate gpio_spec to the GPIO number and flags
  * @gc:		pointer to the gpio_chip structure
  * @np:		device node of the GPIO chip
@@ -308,6 +417,8 @@ void of_gpiochip_add(struct gpio_chip *chip)
 
 	of_gpiochip_add_pin_range(chip);
 	of_node_get(chip->of_node);
+
+	of_gpiochip_scan_hogs(chip);
 }
 
 void of_gpiochip_remove(struct gpio_chip *chip)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 568aa2b..410b86d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -315,6 +315,7 @@ EXPORT_SYMBOL_GPL(gpiochip_add);
 
 /* Forward-declaration */
 static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
+static void gpiochip_free_hogs(struct gpio_chip *chip);
 
 /**
  * gpiochip_remove() - unregister a gpio_chip
@@ -333,6 +334,7 @@ void gpiochip_remove(struct gpio_chip *chip)
 
 	acpi_gpiochip_remove(chip);
 	gpiochip_remove_pin_ranges(chip);
+	gpiochip_free_hogs(chip);
 	of_gpiochip_remove(chip);
 
 	spin_lock_irqsave(&gpio_lock, flags);
@@ -866,6 +868,7 @@ static bool __gpiod_free(struct gpio_desc *desc)
 		clear_bit(FLAG_REQUESTED, &desc->flags);
 		clear_bit(FLAG_OPEN_DRAIN, &desc->flags);
 		clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
+		clear_bit(FLAG_IS_HOGGED, &desc->flags);
 		ret = true;
 	}
 
@@ -1838,6 +1841,47 @@ struct gpio_desc *__must_check __gpiod_get_optional(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(__gpiod_get_optional);
 
+
+/**
+ * gpiod_configure_flags - helper function to configure a given GPIO
+ * @desc:	gpio whose value will be assigned
+ * @con_id:	function within the GPIO consumer
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ *
+ * Return 0 on success, -ENOENT if no GPIO has been assigned to the
+ * requested function and/or index, or another IS_ERR() code if an error
+ * occurred while trying to acquire the GPIO.
+ */
+static int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
+		unsigned long lflags, enum gpiod_flags dflags)
+{
+	int status;
+
+	if (lflags & GPIO_ACTIVE_LOW)
+		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
+	if (lflags & GPIO_OPEN_DRAIN)
+		set_bit(FLAG_OPEN_DRAIN, &desc->flags);
+	if (lflags & GPIO_OPEN_SOURCE)
+		set_bit(FLAG_OPEN_SOURCE, &desc->flags);
+
+	/* No particular flag request, return here... */
+	if (!(dflags & GPIOD_FLAGS_BIT_DIR_SET)) {
+		pr_debug("no flags found for %s\n", con_id);
+		return 0;
+	}
+
+	/* Process flags */
+	if (dflags & GPIOD_FLAGS_BIT_DIR_OUT)
+		status = gpiod_direction_output(desc,
+					      dflags & GPIOD_FLAGS_BIT_DIR_VAL);
+	else
+		status = gpiod_direction_input(desc);
+
+	return status;
+}
+
 /**
  * gpiod_get_index - obtain a GPIO from a multi-index GPIO function
  * @dev:	GPIO consumer, can be NULL for system-global GPIOs
@@ -1887,28 +1931,10 @@ struct gpio_desc *__must_check __gpiod_get_index(struct device *dev,
 	}
 
 	status = gpiod_request(desc, con_id);
-
 	if (status < 0)
 		return ERR_PTR(status);
 
-	if (lookupflags & GPIO_ACTIVE_LOW)
-		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
-	if (lookupflags & GPIO_OPEN_DRAIN)
-		set_bit(FLAG_OPEN_DRAIN, &desc->flags);
-	if (lookupflags & GPIO_OPEN_SOURCE)
-		set_bit(FLAG_OPEN_SOURCE, &desc->flags);
-
-	/* No particular flag request, return here... */
-	if (!(flags & GPIOD_FLAGS_BIT_DIR_SET))
-		return desc;
-
-	/* Process flags */
-	if (flags & GPIOD_FLAGS_BIT_DIR_OUT)
-		status = gpiod_direction_output(desc,
-					      flags & GPIOD_FLAGS_BIT_DIR_VAL);
-	else
-		status = gpiod_direction_input(desc);
-
+	status = gpiod_configure_flags(desc, con_id, lookupflags, flags);
 	if (status < 0) {
 		dev_dbg(dev, "setup of GPIO %s failed\n", con_id);
 		gpiod_put(desc);
@@ -2004,6 +2030,66 @@ struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
 EXPORT_SYMBOL_GPL(__gpiod_get_index_optional);
 
 /**
+ * gpiod_hog - Hog the specified GPIO desc given the provided flags
+ * @desc:	gpio whose value will be assigned
+ * @name:	gpio line name
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ */
+int gpiod_hog(struct gpio_desc *desc, const char *name,
+	      unsigned long lflags, enum gpiod_flags dflags)
+{
+	struct gpio_chip *chip;
+	struct gpio_desc *local_desc;
+	int hwnum;
+	int status;
+
+	chip = gpiod_to_chip(desc);
+	hwnum = gpio_chip_hwgpio(desc);
+
+	local_desc = gpiochip_request_own_desc(chip, hwnum, name);
+	if (IS_ERR(local_desc)) {
+		pr_debug("requesting own GPIO %s failed\n", name);
+		return PTR_ERR(local_desc);
+	}
+
+	status = gpiod_configure_flags(desc, name, lflags, dflags);
+	if (status < 0) {
+		pr_debug("setup of GPIO %s failed\n", name);
+		gpiochip_free_own_desc(desc);
+		return status;
+	}
+
+	/* Mark GPIO as hogged so it can be identified and removed later */
+	set_bit(FLAG_IS_HOGGED, &desc->flags);
+
+	pr_info("GPIO line %d (%s) hogged as %s%s\n",
+		desc_to_gpio(desc), name,
+		(dflags&GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input",
+		(dflags&GPIOD_FLAGS_BIT_DIR_OUT) ?
+		  (dflags&GPIOD_FLAGS_BIT_DIR_VAL) ? "/high" : "/low":"");
+
+	return 0;
+}
+
+/**
+ * gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
+ * @chip:	gpio chip to act on
+ *
+ * This is only used by of_gpiochip_remove to free hogged gpios
+ */
+static void gpiochip_free_hogs(struct gpio_chip *chip)
+{
+	int id;
+
+	for (id = 0; id < chip->ngpio; id++) {
+		if (test_bit(FLAG_IS_HOGGED, &chip->desc[id].flags))
+			gpiochip_free_own_desc(&chip->desc[id]);
+	}
+}
+
+/**
  * gpiod_put - dispose of a GPIO descriptor
  * @desc:	GPIO descriptor to dispose of
  *
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 550a5ea..cadba26 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -78,6 +78,7 @@ struct gpio_desc {
 #define FLAG_OPEN_SOURCE 8	/* Gpio is open source type */
 #define FLAG_USED_AS_IRQ 9	/* GPIO is connected to an IRQ */
 #define FLAG_SYSFS_DIR	10	/* show sysfs direction attribute */
+#define FLAG_IS_HOGGED	11	/* GPIO is hogged */
 
 #define ID_SHIFT	16	/* add new flags before this one */
 
@@ -89,6 +90,8 @@ struct gpio_desc {
 
 int gpiod_request(struct gpio_desc *desc, const char *label);
 void gpiod_free(struct gpio_desc *desc);
+int gpiod_hog(struct gpio_desc *desc, const char *name,
+		unsigned long lflags, enum gpiod_flags dflags);
 
 /*
  * Return the GPIO number of the passed descriptor relative to its chip
-- 
1.8.5.1

[Patch v6 1/2] gpio: add GPIO hogging mechanism

[Benoit Parrot]

Based on Boris Brezillion's work this is a reworked patch
of his initial GPIO hogging mechanism.
This patch provides a way to initially configure specific GPIO
when the GPIO controller is probed.

The actual DT scanning to collect the GPIO specific data is performed
as part of gpiochip_add().

The purpose of this is to allow specific GPIOs to be configured
without any driver specific code.
This is particularly useful because board design are getting
increasingly complex and given SoC pins can now have more
than 10 mux values, a lot of connections are now dependent on
external IO muxes to switch various modes.

Specific drivers should not necessarily need to be aware of
what accounts to a specific board implementation. This board level
"description" should be best kept as part of the dts file.

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/gpio/gpiolib-of.c | 111 +++++++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpiolib.c    | 124 +++++++++++++++++++++++++++++++++++++++-------
 drivers/gpio/gpiolib.h    |   3 ++
 3 files changed, 219 insertions(+), 19 deletions(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 08261f2..cfb50b4 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -22,6 +22,7 @@
 #include <linux/of_gpio.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/slab.h>
+#include <linux/gpio/machine.h>
 
 #include "gpiolib.h"
 
@@ -117,6 +118,114 @@ int of_get_named_gpio_flags(struct device_node *np, const char *list_name,
 EXPORT_SYMBOL(of_get_named_gpio_flags);
 
 /**
+ * of_get_gpio_hog() - Get a GPIO hog descriptor, names and flags for GPIO API
+ * @np:		device node to get GPIO from
+ * @name:	GPIO line name
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ *
+ * Returns GPIO descriptor to use with Linux GPIO API, or one of the errno
+ * value on the error condition.
+ */
+static struct gpio_desc *of_get_gpio_hog(struct device_node *np,
+				  const char **name,
+				  enum gpio_lookup_flags *lflags,
+				  enum gpiod_flags *dflags)
+{
+	struct device_node *chip_np;
+	enum of_gpio_flags xlate_flags;
+	struct gpio_desc *desc;
+	struct gg_data gg_data = {
+		.flags = &xlate_flags,
+	};
+	u32 tmp;
+	int i, ret;
+
+	chip_np = np->parent;
+	if (!chip_np)
+		return ERR_PTR(-EINVAL);
+
+	xlate_flags = 0;
+	*lflags = 0;
+	*dflags = 0;
+
+	ret = of_property_read_u32(chip_np, "#gpio-cells", &tmp);
+	if (ret)
+		return ERR_PTR(ret);
+
+	if (tmp > MAX_PHANDLE_ARGS)
+		return ERR_PTR(-EINVAL);
+
+	gg_data.gpiospec.args_count = tmp;
+	gg_data.gpiospec.np = chip_np;
+	for (i = 0; i < tmp; i++) {
+		ret = of_property_read_u32_index(np, "gpios", i,
+					   &gg_data.gpiospec.args[i]);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
+	gpiochip_find(&gg_data, of_gpiochip_find_and_xlate);
+	if (!gg_data.out_gpio) {
+		if (np->parent == np)
+			return ERR_PTR(-ENXIO);
+		else
+			return ERR_PTR(-EINVAL);
+	}
+
+	if (xlate_flags & OF_GPIO_ACTIVE_LOW)
+		*lflags |= GPIO_ACTIVE_LOW;
+
+	if (of_property_read_bool(np, "input"))
+		*dflags |= GPIOD_IN;
+	else if (of_property_read_bool(np, "output-low"))
+		*dflags |= GPIOD_OUT_LOW;
+	else if (of_property_read_bool(np, "output-high"))
+		*dflags |= GPIOD_OUT_HIGH;
+	else {
+		pr_warn("GPIO line %d (%s): no hogging state specified, bailing out\n",
+			desc_to_gpio(gg_data.out_gpio), np->name);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (name && of_property_read_string(np, "line-name", name))
+		*name = np->name;
+
+	desc = gg_data.out_gpio;
+
+	return desc;
+}
+
+/**
+ * of_gpiochip_scan_hogs - Scan gpio-controller and apply GPIO hog as requested
+ * @chip:	gpio chip to act on
+ *
+ * This is only used by of_gpiochip_add to request/set GPIO initial
+ * configuration.
+ */
+static void of_gpiochip_scan_hogs(struct gpio_chip *chip)
+{
+	struct gpio_desc *desc = NULL;
+	struct device_node *np;
+	const char *name;
+	enum gpio_lookup_flags lflags;
+	enum gpiod_flags dflags;
+
+	for_each_child_of_node(chip->of_node, np) {
+		if (!of_property_read_bool(np, "gpio-hog"))
+			continue;
+
+		desc = of_get_gpio_hog(np, &name, &lflags, &dflags);
+		if (IS_ERR(desc))
+			continue;
+
+		if (gpiod_hog(desc, name, lflags, dflags))
+			continue;
+	}
+}
+
+/**
  * of_gpio_simple_xlate - translate gpio_spec to the GPIO number and flags
  * @gc:		pointer to the gpio_chip structure
  * @np:		device node of the GPIO chip
@@ -308,6 +417,8 @@ void of_gpiochip_add(struct gpio_chip *chip)
 
 	of_gpiochip_add_pin_range(chip);
 	of_node_get(chip->of_node);
+
+	of_gpiochip_scan_hogs(chip);
 }
 
 void of_gpiochip_remove(struct gpio_chip *chip)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 568aa2b..410b86d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -315,6 +315,7 @@ EXPORT_SYMBOL_GPL(gpiochip_add);
 
 /* Forward-declaration */
 static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
+static void gpiochip_free_hogs(struct gpio_chip *chip);
 
 /**
  * gpiochip_remove() - unregister a gpio_chip
@@ -333,6 +334,7 @@ void gpiochip_remove(struct gpio_chip *chip)
 
 	acpi_gpiochip_remove(chip);
 	gpiochip_remove_pin_ranges(chip);
+	gpiochip_free_hogs(chip);
 	of_gpiochip_remove(chip);
 
 	spin_lock_irqsave(&gpio_lock, flags);
@@ -866,6 +868,7 @@ static bool __gpiod_free(struct gpio_desc *desc)
 		clear_bit(FLAG_REQUESTED, &desc->flags);
 		clear_bit(FLAG_OPEN_DRAIN, &desc->flags);
 		clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
+		clear_bit(FLAG_IS_HOGGED, &desc->flags);
 		ret = true;
 	}
 
@@ -1838,6 +1841,47 @@ struct gpio_desc *__must_check __gpiod_get_optional(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(__gpiod_get_optional);
 
+
+/**
+ * gpiod_configure_flags - helper function to configure a given GPIO
+ * @desc:	gpio whose value will be assigned
+ * @con_id:	function within the GPIO consumer
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ *
+ * Return 0 on success, -ENOENT if no GPIO has been assigned to the
+ * requested function and/or index, or another IS_ERR() code if an error
+ * occurred while trying to acquire the GPIO.
+ */
+static int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
+		unsigned long lflags, enum gpiod_flags dflags)
+{
+	int status;
+
+	if (lflags & GPIO_ACTIVE_LOW)
+		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
+	if (lflags & GPIO_OPEN_DRAIN)
+		set_bit(FLAG_OPEN_DRAIN, &desc->flags);
+	if (lflags & GPIO_OPEN_SOURCE)
+		set_bit(FLAG_OPEN_SOURCE, &desc->flags);
+
+	/* No particular flag request, return here... */
+	if (!(dflags & GPIOD_FLAGS_BIT_DIR_SET)) {
+		pr_debug("no flags found for %s\n", con_id);
+		return 0;
+	}
+
+	/* Process flags */
+	if (dflags & GPIOD_FLAGS_BIT_DIR_OUT)
+		status = gpiod_direction_output(desc,
+					      dflags & GPIOD_FLAGS_BIT_DIR_VAL);
+	else
+		status = gpiod_direction_input(desc);
+
+	return status;
+}
+
 /**
  * gpiod_get_index - obtain a GPIO from a multi-index GPIO function
  * @dev:	GPIO consumer, can be NULL for system-global GPIOs
@@ -1887,28 +1931,10 @@ struct gpio_desc *__must_check __gpiod_get_index(struct device *dev,
 	}
 
 	status = gpiod_request(desc, con_id);
-
 	if (status < 0)
 		return ERR_PTR(status);
 
-	if (lookupflags & GPIO_ACTIVE_LOW)
-		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
-	if (lookupflags & GPIO_OPEN_DRAIN)
-		set_bit(FLAG_OPEN_DRAIN, &desc->flags);
-	if (lookupflags & GPIO_OPEN_SOURCE)
-		set_bit(FLAG_OPEN_SOURCE, &desc->flags);
-
-	/* No particular flag request, return here... */
-	if (!(flags & GPIOD_FLAGS_BIT_DIR_SET))
-		return desc;
-
-	/* Process flags */
-	if (flags & GPIOD_FLAGS_BIT_DIR_OUT)
-		status = gpiod_direction_output(desc,
-					      flags & GPIOD_FLAGS_BIT_DIR_VAL);
-	else
-		status = gpiod_direction_input(desc);
-
+	status = gpiod_configure_flags(desc, con_id, lookupflags, flags);
 	if (status < 0) {
 		dev_dbg(dev, "setup of GPIO %s failed\n", con_id);
 		gpiod_put(desc);
@@ -2004,6 +2030,66 @@ struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
 EXPORT_SYMBOL_GPL(__gpiod_get_index_optional);
 
 /**
+ * gpiod_hog - Hog the specified GPIO desc given the provided flags
+ * @desc:	gpio whose value will be assigned
+ * @name:	gpio line name
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ */
+int gpiod_hog(struct gpio_desc *desc, const char *name,
+	      unsigned long lflags, enum gpiod_flags dflags)
+{
+	struct gpio_chip *chip;
+	struct gpio_desc *local_desc;
+	int hwnum;
+	int status;
+
+	chip = gpiod_to_chip(desc);
+	hwnum = gpio_chip_hwgpio(desc);
+
+	local_desc = gpiochip_request_own_desc(chip, hwnum, name);
+	if (IS_ERR(local_desc)) {
+		pr_debug("requesting own GPIO %s failed\n", name);
+		return PTR_ERR(local_desc);
+	}
+
+	status = gpiod_configure_flags(desc, name, lflags, dflags);
+	if (status < 0) {
+		pr_debug("setup of GPIO %s failed\n", name);
+		gpiochip_free_own_desc(desc);
+		return status;
+	}
+
+	/* Mark GPIO as hogged so it can be identified and removed later */
+	set_bit(FLAG_IS_HOGGED, &desc->flags);
+
+	pr_info("GPIO line %d (%s) hogged as %s%s\n",
+		desc_to_gpio(desc), name,
+		(dflags&GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input",
+		(dflags&GPIOD_FLAGS_BIT_DIR_OUT) ?
+		  (dflags&GPIOD_FLAGS_BIT_DIR_VAL) ? "/high" : "/low":"");
+
+	return 0;
+}
+
+/**
+ * gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
+ * @chip:	gpio chip to act on
+ *
+ * This is only used by of_gpiochip_remove to free hogged gpios
+ */
+static void gpiochip_free_hogs(struct gpio_chip *chip)
+{
+	int id;
+
+	for (id = 0; id < chip->ngpio; id++) {
+		if (test_bit(FLAG_IS_HOGGED, &chip->desc[id].flags))
+			gpiochip_free_own_desc(&chip->desc[id]);
+	}
+}
+
+/**
  * gpiod_put - dispose of a GPIO descriptor
  * @desc:	GPIO descriptor to dispose of
  *
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 550a5ea..cadba26 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -78,6 +78,7 @@ struct gpio_desc {
 #define FLAG_OPEN_SOURCE 8	/* Gpio is open source type */
 #define FLAG_USED_AS_IRQ 9	/* GPIO is connected to an IRQ */
 #define FLAG_SYSFS_DIR	10	/* show sysfs direction attribute */
+#define FLAG_IS_HOGGED	11	/* GPIO is hogged */
 
 #define ID_SHIFT	16	/* add new flags before this one */
 
@@ -89,6 +90,8 @@ struct gpio_desc {
 
 int gpiod_request(struct gpio_desc *desc, const char *label);
 void gpiod_free(struct gpio_desc *desc);
+int gpiod_hog(struct gpio_desc *desc, const char *name,
+		unsigned long lflags, enum gpiod_flags dflags);
 
 /*
  * Return the GPIO number of the passed descriptor relative to its chip
-- 
1.8.5.1

[Patch v6 2/2] gpio: Document GPIO hogging mechanism

[Benoit Parrot]

Add GPIO hogging documentation to gpio.txt

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
---
 Documentation/devicetree/bindings/gpio/gpio.txt | 30 +++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index b9bd1d6..a0ce2bd 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -115,6 +115,29 @@ Every GPIO controller node must contain both an empty "gpio-controller"
 property, and a #gpio-cells integer property, which indicates the number of
 cells in a gpio-specifier.
 
+The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
+providing automatic GPIO request and configuration as part of the
+gpio-controller's driver probe function.
+
+Each GPIO hog definition is represented as a child node of the GPIO controller.
+Required properties:
+- gpio-hog:   A property specifying that this child node represent a GPIO hog.
+- gpios:      Store the GPIO information (id, flags, ...). Shall contain the
+	      number of cells specified in its parent node (GPIO controller
+	      node).
+Only one of the following properties scanned in the order shown below.
+This means that when multiple properties are present they will be searched
+in the order presented below and the first match is taken as the intended
+configuration.
+- input:      A property specifying to set the GPIO direction as input.
+- output-low  A property specifying to set the GPIO direction as output with
+	      the value low.
+- output-high A property specifying to set the GPIO direction as output with
+	      the value high.
+
+Optional properties:
+- line-name:  The GPIO label name. If not present the node name is used.
+
 Example of two SOC GPIO banks defined as gpio-controller nodes:
 
 	qe_pio_a: gpio-controller@1400 {
@@ -122,6 +145,13 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
 		reg = <0x1400 0x18>;
 		gpio-controller;
 		#gpio-cells = <2>;
+
+		line_b {
+			gpio-hog;
+			gpios = <6 0>;
+			output-low;
+			line-name = "foo-bar-gpio";
+		};
 	};
 
 	qe_pio_e: gpio-controller@1460 {
-- 
1.8.5.1

[Patch v6 2/2] gpio: Document GPIO hogging mechanism

[Benoit Parrot]

Add GPIO hogging documentation to gpio.txt

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
---
 Documentation/devicetree/bindings/gpio/gpio.txt | 30 +++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index b9bd1d6..a0ce2bd 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -115,6 +115,29 @@ Every GPIO controller node must contain both an empty "gpio-controller"
 property, and a #gpio-cells integer property, which indicates the number of
 cells in a gpio-specifier.
 
+The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
+providing automatic GPIO request and configuration as part of the
+gpio-controller's driver probe function.
+
+Each GPIO hog definition is represented as a child node of the GPIO controller.
+Required properties:
+- gpio-hog:   A property specifying that this child node represent a GPIO hog.
+- gpios:      Store the GPIO information (id, flags, ...). Shall contain the
+	      number of cells specified in its parent node (GPIO controller
+	      node).
+Only one of the following properties scanned in the order shown below.
+This means that when multiple properties are present they will be searched
+in the order presented below and the first match is taken as the intended
+configuration.
+- input:      A property specifying to set the GPIO direction as input.
+- output-low  A property specifying to set the GPIO direction as output with
+	      the value low.
+- output-high A property specifying to set the GPIO direction as output with
+	      the value high.
+
+Optional properties:
+- line-name:  The GPIO label name. If not present the node name is used.
+
 Example of two SOC GPIO banks defined as gpio-controller nodes:
 
 	qe_pio_a: gpio-controller@1400 {
@@ -122,6 +145,13 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
 		reg = <0x1400 0x18>;
 		gpio-controller;
 		#gpio-cells = <2>;
+
+		line_b {
+			gpio-hog;
+			gpios = <6 0>;
+			output-low;
+			line-name = "foo-bar-gpio";
+		};
 	};
 
 	qe_pio_e: gpio-controller@1460 {
-- 
1.8.5.1

Re: [Patch v6 0/2] gpio: add GPIO hogging mechanism

[Alexandre Courbot]

Linus, this looks good to me in its current form, what are your thoughts?

On Tue, Feb 3, 2015 at 2:44 AM, Benoit Parrot <bparrot@ti.com> wrote:
> This patch set re-introduces the gpio hogging concept first
> presented by Boris Brezillion.
> This patch set provides a way to initially configure specific GPIO
> when the GPIO controller is probed.
>
> The actual DT scanning to collect the GPIO specific data is performed
> as part of of_gpiochip_add().
>
> The purpose of this is to allow specific GPIOs to be configured
> without any driver specific code.
> This is particularly useful because board design are getting
> increasingly complex and given SoC pins can now have more
> than 10 mux values a lot of connections are now dependent on
> external IO muxes to switch various modes.
>
> Specific drivers should not necessarily need to be aware of
> what accounts to a specific board implementation. This board level
> "description" should be best kept as part of the dts file.
>
> Changes since v5:
>  * Addressed review comment from Linus Walleij
>  * Replace "state" property back with separate boolean properties
>  * Renamed helper function
>  * Refactored pr_* calls to remove "__func__"
>
> Changes since v4:
>  * Addressed review comments from Alexandre Courbot
>
> Changes since v3:
>  * Relocated the non-DT "hog" function to gpiolib.c.
>  * Rename some of the function to be clearer and remove _ prefixes.
>  * Replace the gpiod_request/gpiod_put usage with
>    gpiochip_request_own_desc/free_own_desc version instead.
>  * Refactor some of the logic to better handle error condition/reporting
>  * Renamed the "direction" DT properties to "state".
>
> Changes since v2:
>  * Refactor the gpio-hog mechanism to split the DT related action
>    from the actual "hogging" operation.
>  * This allows non-DT providers to implement hogs as well.
>  * Added FLAG_IS_HOGGED to mark hogged gpio and make gpiochip removal
>    able to release hogged gpio.
>  * Similarly to the hogging, the cleanup is performed as part of
>    of_gpiochip_remove
>
> Changes since v1:
>  * Split the devicetree bindings documentation in its own patch.
>  * Refactor the gpio-hog mechanism as private functions meant to
>    be to invoked from of_gpiochip_add().
>
>
> Benoit Parrot (2):
>   gpio: add GPIO hogging mechanism
>   gpio: Document GPIO hogging mechanism
>
>  Documentation/devicetree/bindings/gpio/gpio.txt |  30 ++++++
>  drivers/gpio/gpiolib-of.c                       | 111 +++++++++++++++++++++
>  drivers/gpio/gpiolib.c                          | 124 ++++++++++++++++++++----
>  drivers/gpio/gpiolib.h                          |   3 +
>  4 files changed, 249 insertions(+), 19 deletions(-)
>
> --
> 1.8.5.1
>

Re: [Patch v6 1/2] gpio: add GPIO hogging mechanism

[Linus Walleij]

On Mon, Feb 2, 2015 at 6:44 PM, Benoit Parrot <bparrot@ti.com> wrote:

> Based on Boris Brezillion's work this is a reworked patch
> of his initial GPIO hogging mechanism.
> This patch provides a way to initially configure specific GPIO
> when the GPIO controller is probed.
>
> The actual DT scanning to collect the GPIO specific data is performed
> as part of gpiochip_add().
>
> The purpose of this is to allow specific GPIOs to be configured
> without any driver specific code.
> This is particularly useful because board design are getting
> increasingly complex and given SoC pins can now have more
> than 10 mux values, a lot of connections are now dependent on
> external IO muxes to switch various modes.
>
> Specific drivers should not necessarily need to be aware of
> what accounts to a specific board implementation. This board level
> "description" should be best kept as part of the dts file.
>
> Signed-off-by: Benoit Parrot <bparrot@ti.com>
> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

Patch applied.

Good to have this in place for Linux 4.1!

Yours,
Linus Walleij

Re: [Patch v6 2/2] gpio: Document GPIO hogging mechanism

[Linus Walleij]

On Mon, Feb 2, 2015 at 6:44 PM, Benoit Parrot <bparrot@ti.com> wrote:

> Add GPIO hogging documentation to gpio.txt
>
> Signed-off-by: Benoit Parrot <bparrot@ti.com>
> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

Patch applied.

Yours,
Linus Walleij