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Message-Id: <20250610-gpio-sysfs-chip-export-v1-14-a8c7aa4478b1@linaro.org>
Date: Tue, 10 Jun 2025 16:38:29 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>,
Kent Gibson <warthog618@...il.com>,
Jan Lübbe <jlu@...gutronix.de>,
Marek Vasut <marex@...x.de>, Geert Uytterhoeven <geert+renesas@...der.be>,
Linus Walleij <linus.walleij@...aro.org>,
Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH RFC/RFT 14/15] gpio: sysfs: allow disabling the legacy
parts of the GPIO sysfs interface
From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
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.
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
drivers/gpio/Kconfig | 8 ++++++++
drivers/gpio/gpiolib-sysfs.c | 32 ++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+)
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 44f922e10db2f8dcbdacf79ccd27b0fd9cd93564..d040fdd95ee4b19851057fbedbb023f277149c9c 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -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
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index d8c17d71d5458011d15bc4239bd4c041244da3fd..48e1353f966837d46f00b552f870440097ecfe18 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -46,7 +46,9 @@ struct gpiod_data {
struct device *dev;
struct mutex mutex;
+#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)
struct kernfs_node *value_class_node;
+#endif /* CONFIG_GPIO_SYSFS_LEGACY */
struct kernfs_node *value_chip_node;
int irq;
unsigned char irq_flags;
@@ -67,7 +69,9 @@ struct gpiod_data {
struct gpiodev_data {
struct gpio_device *gdev;
+#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)
struct device *cdev_base; /* Class device by GPIO base */
+#endif /* CONFIG_GPIO_SYSFS_LEGACY */
struct device *cdev_id; /* Class device by GPIO device ID */
struct list_head exported_lines;
};
@@ -181,7 +185,9 @@ static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
{
struct gpiod_data *data = priv;
+#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)
sysfs_notify_dirent(data->value_class_node);
+#endif /* CONFIG_GPIO_SYSFS_LEGACY */
kernfs_notify(data->value_chip_node);
return IRQ_HANDLED;
@@ -416,6 +422,7 @@ 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)
{
@@ -424,6 +431,7 @@ 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)
@@ -548,6 +556,7 @@ 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,
@@ -555,6 +564,7 @@ static struct attribute *gpiochip_attrs[] = {
NULL,
};
ATTRIBUTE_GROUPS(gpiochip);
+#endif /* CONFIG_GPIO_SYSFS_LEGACY */
static struct attribute *gpiochip_ext_attrs[] = {
&dev_attr_label.attr,
@@ -565,6 +575,7 @@ 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)
@@ -629,10 +640,13 @@ 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)
@@ -763,6 +777,7 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
* at least one known user of gpiod_export_link() in the tree. This
* function still uses class_find_device() internally.
*/
+#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)
desc_data->dev = device_create_with_groups(&gpio_class, &gdev->dev,
MKDEV(0, 0), desc_data,
desc_data->attr_groups,
@@ -779,6 +794,7 @@ 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) {
@@ -822,10 +838,12 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
err_free_name:
kfree(desc_data->attr_group.name);
err_put_dirent:
+#if IS_ENABLED(CONFIG_GPIO_SYSFS_LEGACY)
sysfs_put(desc_data->value_class_node);
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);
@@ -834,12 +852,14 @@ 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 data->desc == desc;
}
+#endif /* CONFIG_GPIO_SYSFS_LEGACY */
/**
* gpiod_export_link - create a sysfs link to an exported GPIO node
@@ -856,6 +876,7 @@ 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;
@@ -872,6 +893,9 @@ 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);
@@ -910,8 +934,10 @@ 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_class_node);
device_unregister(desc_data->dev);
+#endif /* CONFIG_GPIO_SYSFS_LEGACY */
kernfs_put(desc_data->value_chip_node);
/*
@@ -966,6 +992,7 @@ 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,
@@ -976,13 +1003,16 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
kfree(data);
return PTR_ERR(data->cdev_base);
}
+#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 */
kfree(data);
return PTR_ERR(data->cdev_id);
}
@@ -1001,7 +1031,9 @@ 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);
}
--
2.48.1
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