Commit e69c6db4 authored by Bartosz Golaszewski's avatar Bartosz Golaszewski
Browse files

gpio: sysfs: allow disabling the legacy parts of the GPIO sysfs interface 



Add a Kconfig switch allowing to disable the legacy parts of the GPIO
sysfs interface. This means that even though we keep the
/sys/class/gpio/ directory, it no longer contains the global
export/unexport attribute pair (instead, the user should use the
per-chip export/unpexport) nor the gpiochip$BASE entries. This option
default to y if GPIO sysfs is enabled but we'll default it to n at some
point in the future.

Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250704-gpio-sysfs-chip-export-v4-9-9289d8758243@linaro.org


Signed-off-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
parent 4fa93223

drivers/gpio/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -69,6 +69,14 @@ config GPIO_SYSFS 
	  use the character device /dev/gpiochipN with the appropriate

	  ioctl() operations instead.



config GPIO_SYSFS_LEGACY

	bool "Enable legacy functionalities of the sysfs interface"

	depends on GPIO_SYSFS

	default y if GPIO_SYSFS

	help

	  Say Y here if you want to enable the legacy, global GPIO

	  numberspace-based functionalities of the sysfs interface.



config GPIO_CDEV

	bool "Character device (/dev/gpiochipN) support" if EXPERT

	default y

drivers/gpio/gpiolib-sysfs.c

+42 −0
Original line number Diff line number Diff line
@@ -24,6 +24,8 @@ 
#include "gpiolib.h"

#include "gpiolib-sysfs.h"



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)



struct kernfs_node;



#define GPIO_IRQF_TRIGGER_NONE		0
@@ -41,6 +43,8 @@ enum { 
	GPIO_SYSFS_LINE_CLASS_ATTR_SIZE,

};



#endif /* CONFIG_GPIO_SYSFS_LEGACY */



enum {

	GPIO_SYSFS_LINE_CHIP_ATTR_DIRECTION = 0,

	GPIO_SYSFS_LINE_CHIP_ATTR_VALUE,
@@ -55,21 +59,26 @@ struct gpiod_data { 
	struct device *dev;



	struct mutex mutex;

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	struct kernfs_node *value_kn;

	int irq;

	unsigned char irq_flags;

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



	bool direction_can_change;



	struct kobject *parent;

	struct device_attribute dir_attr;

	struct device_attribute val_attr;



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	struct device_attribute edge_attr;

	struct device_attribute active_low_attr;



	struct attribute *class_attrs[GPIO_SYSFS_LINE_CLASS_ATTR_SIZE];

	struct attribute_group class_attr_group;

	const struct attribute_group *class_attr_groups[2];

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



	struct attribute *chip_attrs[GPIO_SYSFS_LINE_CHIP_ATTR_SIZE];

	struct attribute_group chip_attr_group;
@@ -80,7 +89,9 @@ struct gpiodev_data { 
	struct list_head exported_lines;

	struct gpio_device *gdev;

	struct device *cdev_id; /* Class device by GPIO device ID */

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	struct device *cdev_base; /* Class device by GPIO base */

#endif /* CONFIG_GPIO_SYSFS_LEGACY */

};



/*
@@ -188,6 +199,7 @@ static ssize_t value_store(struct device *dev, struct device_attribute *attr, 
	return size;

}



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

static irqreturn_t gpio_sysfs_irq(int irq, void *priv)

{

	struct gpiod_data *data = priv;
@@ -383,6 +395,7 @@ static ssize_t active_low_store(struct device *dev, 


	return gpio_sysfs_set_active_low(data, value) ?: size;

}

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,

			       int n)
@@ -397,6 +410,7 @@ static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr, 


		if (!data->direction_can_change)

			mode = 0;

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	} else if (strcmp(attr->name, "edge") == 0) {

		data = container_of(dev_attr, struct gpiod_data, edge_attr);
@@ -406,6 +420,7 @@ static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr, 
		if (!data->direction_can_change &&

		    test_bit(FLAG_IS_OUT, &data->desc->flags))

			mode = 0;

#endif /* CONFIG_GPIO_SYSFS_LEGACY */

	}



	return mode;
@@ -426,6 +441,7 @@ static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr, 
 *   /ngpio ... matching gpio_chip.ngpio

 */



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

static ssize_t base_show(struct device *dev, struct device_attribute *attr,

			 char *buf)

{
@@ -434,6 +450,7 @@ static ssize_t base_show(struct device *dev, struct device_attribute *attr, 
	return sysfs_emit(buf, "%u\n", data->gdev->base);

}

static DEVICE_ATTR_RO(base);

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



static ssize_t label_show(struct device *dev, struct device_attribute *attr,

			  char *buf)
@@ -558,6 +575,7 @@ static struct device_attribute dev_attr_unexport = __ATTR(unexport, 0200, 
							  NULL,

							  chip_unexport_store);



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

static struct attribute *gpiochip_attrs[] = {

	&dev_attr_base.attr,

	&dev_attr_label.attr,
@@ -565,6 +583,7 @@ static struct attribute *gpiochip_attrs[] = { 
	NULL,

};

ATTRIBUTE_GROUPS(gpiochip);

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



static struct attribute *gpiochip_ext_attrs[] = {

	&dev_attr_label.attr,
@@ -575,6 +594,7 @@ static struct attribute *gpiochip_ext_attrs[] = { 
};

ATTRIBUTE_GROUPS(gpiochip_ext);



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

/*

 * /sys/class/gpio/export ... write-only

 *	integer N ... number of GPIO to export (full access)
@@ -639,10 +659,13 @@ static struct attribute *gpio_class_attrs[] = { 
	NULL,

};

ATTRIBUTE_GROUPS(gpio_class);

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



static const struct class gpio_class = {

	.name =		"gpio",

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	.class_groups =	gpio_class_groups,

#endif /* CONFIG_GPIO_SYSFS_LEGACY */

};



static int match_gdev(struct device *dev, const void *desc)
@@ -754,6 +777,8 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change) 
	gpiod_attr_init(&desc_data->dir_attr, "direction",

			direction_show, direction_store);

	gpiod_attr_init(&desc_data->val_attr, "value", value_show, value_store);



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	gpiod_attr_init(&desc_data->edge_attr, "edge", edge_show, edge_store);

	gpiod_attr_init(&desc_data->active_low_attr, "active_low",

			active_low_show, active_low_store);
@@ -789,6 +814,7 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change) 
		status = -ENODEV;

		goto err_unregister_device;

	}

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



	gdev_data = gdev_get_data(gdev);

	if (!gdev_data) {
@@ -832,10 +858,12 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change) 
err_free_name:

	kfree(desc_data->chip_attr_group.name);

err_put_dirent:

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	sysfs_put(desc_data->value_kn);

err_unregister_device:

	device_unregister(desc_data->dev);

err_free_data:

#endif /* CONFIG_GPIO_SYSFS_LEGACY */

	kfree(desc_data);

err_clear_bit:

	clear_bit(FLAG_EXPORT, &desc->flags);
@@ -844,12 +872,14 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change) 
}

EXPORT_SYMBOL_GPL(gpiod_export);



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

static int match_export(struct device *dev, const void *desc)

{

	struct gpiod_data *data = dev_get_drvdata(dev);



	return gpiod_is_equal(data->desc, desc);

}

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



/**

 * gpiod_export_link - create a sysfs link to an exported GPIO node
@@ -866,6 +896,7 @@ static int match_export(struct device *dev, const void *desc) 
int gpiod_export_link(struct device *dev, const char *name,

		      struct gpio_desc *desc)

{

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	struct device *cdev;

	int ret;
@@ -882,6 +913,9 @@ int gpiod_export_link(struct device *dev, const char *name, 
	put_device(cdev);



	return ret;

#else

	return -EOPNOTSUPP;

#endif /* CONFIG_GPIO_SYSFS_LEGACY */

}

EXPORT_SYMBOL_GPL(gpiod_export_link);
@@ -920,6 +954,7 @@ void gpiod_unexport(struct gpio_desc *desc) 


		list_del(&desc_data->list);

		clear_bit(FLAG_EXPORT, &desc->flags);

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

		sysfs_put(desc_data->value_kn);

		device_unregister(desc_data->dev);
@@ -929,6 +964,7 @@ void gpiod_unexport(struct gpio_desc *desc) 
		 */

		if (desc_data->irq_flags)

			gpio_sysfs_free_irq(desc_data);

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



		sysfs_remove_groups(desc_data->parent,

				    desc_data->chip_attr_groups);
@@ -979,6 +1015,7 @@ int gpiochip_sysfs_register(struct gpio_device *gdev) 


	guard(mutex)(&sysfs_lock);



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

	/* use chip->base for the ID; it's already known to be unique */

	data->cdev_base = device_create_with_groups(&gpio_class, parent,

						    MKDEV(0, 0), data,
@@ -990,13 +1027,16 @@ int gpiochip_sysfs_register(struct gpio_device *gdev) 
		kfree(data);

		return err;

	}

#endif /* CONFIG_GPIO_SYSFS_LEGACY */



	data->cdev_id = device_create_with_groups(&gpio_class, parent,

						  MKDEV(0, 0), data,

						  gpiochip_ext_groups,

						  "chip%d", gdev->id);

	if (IS_ERR(data->cdev_id)) {

#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

		device_unregister(data->cdev_base);

#endif /* CONFIG_GPIO_SYSFS_LEGACY */

		err = PTR_ERR(data->cdev_id);

		kfree(data);

		return err;
@@ -1016,7 +1056,9 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev) 
		if (!data)

			return;



#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)

		device_unregister(data->cdev_base);

#endif /* CONFIG_GPIO_SYSFS_LEGACY */

		device_unregister(data->cdev_id);

		kfree(data);

	}