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gpio: sysfs: export the GPIO directory locally in the gpiochip<id> directory

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As a way to allow the user-space to stop referring to GPIOs by their
global numbers, introduce a parallel group of line attributes for
exported GPIO that live inside the GPIO chip class device and are
referred to by their HW offset within their parent chip.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250704-gpio-sysfs-chip-export-v4-8-9289d8758243@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
This commit is contained in:
Bartosz Golaszewski
2025-07-04 14:58:55 +02:00
parent 1cd53df733
commit 4fa93223e0
2 changed files with 53 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/ABI/obsolete/sysfs-gpio
View File

@@ -27,6 +27,9 @@ Description:
/base ... (r/o) same as N
/label ... (r/o) descriptive chip name
/ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
/gpio<OFFSET>
/value ... always readable, writes fail for input GPIOs
/direction ... r/w as: in, out (default low); write: high, low
/chipX ... for each gpiochip; #X is the gpio device ID
/export ... asks the kernel to export a GPIO at HW offset X to userspace
/unexport ... to return a GPIO at HW offset X to the kernel

51
drivers/gpio/gpiolib-sysfs.c
View File

@@ -41,6 +41,13 @@ enum {
GPIO_SYSFS_LINE_CLASS_ATTR_SIZE,
};
enum {
GPIO_SYSFS_LINE_CHIP_ATTR_DIRECTION = 0,
GPIO_SYSFS_LINE_CHIP_ATTR_VALUE,
GPIO_SYSFS_LINE_CHIP_ATTR_SENTINEL,
GPIO_SYSFS_LINE_CHIP_ATTR_SIZE,
};
struct gpiod_data {
struct list_head list;
@@ -54,6 +61,7 @@ struct gpiod_data {
bool direction_can_change;
struct kobject *parent;
struct device_attribute dir_attr;
struct device_attribute val_attr;
struct device_attribute edge_attr;
@@ -62,6 +70,10 @@ struct gpiod_data {
struct attribute *class_attrs[GPIO_SYSFS_LINE_CLASS_ATTR_SIZE];
struct attribute_group class_attr_group;
const struct attribute_group *class_attr_groups[2];
struct attribute *chip_attrs[GPIO_SYSFS_LINE_CHIP_ATTR_SIZE];
struct attribute_group chip_attr_group;
const struct attribute_group *chip_attr_groups[2];
};
struct gpiodev_data {
@@ -691,6 +703,7 @@ static void gpiod_attr_init(struct device_attribute *dev_attr, const char *name,
*/
int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
{
char *path __free(kfree) = NULL;
struct gpiodev_data *gdev_data;
struct gpiod_data *desc_data;
struct gpio_device *gdev;
@@ -780,13 +793,46 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
gdev_data = gdev_get_data(gdev);
if (!gdev_data) {
status = -ENODEV;
goto err_unregister_device;
goto err_put_dirent;
}
desc_data->chip_attr_group.name = kasprintf(GFP_KERNEL, "gpio%u",
gpio_chip_hwgpio(desc));
if (!desc_data->chip_attr_group.name) {
status = -ENOMEM;
goto err_put_dirent;
}
attrs = desc_data->chip_attrs;
desc_data->chip_attr_group.is_visible = gpio_is_visible;
attrs[GPIO_SYSFS_LINE_CHIP_ATTR_DIRECTION] = &desc_data->dir_attr.attr;
attrs[GPIO_SYSFS_LINE_CHIP_ATTR_VALUE] = &desc_data->val_attr.attr;
desc_data->chip_attr_group.attrs = attrs;
desc_data->chip_attr_groups[0] = &desc_data->chip_attr_group;
desc_data->parent = &gdev_data->cdev_id->kobj;
status = sysfs_create_groups(desc_data->parent,
desc_data->chip_attr_groups);
if (status)
goto err_free_name;
path = kasprintf(GFP_KERNEL, "gpio%u/value", gpio_chip_hwgpio(desc));
if (!path) {
status = -ENOMEM;
goto err_remove_groups;
}
list_add(&desc_data->list, &gdev_data->exported_lines);
return 0;
err_remove_groups:
sysfs_remove_groups(desc_data->parent, desc_data->chip_attr_groups);
err_free_name:
kfree(desc_data->chip_attr_group.name);
err_put_dirent:
sysfs_put(desc_data->value_kn);
err_unregister_device:
device_unregister(desc_data->dev);
err_free_data:
@@ -883,6 +929,9 @@ void gpiod_unexport(struct gpio_desc *desc)
*/
if (desc_data->irq_flags)
gpio_sysfs_free_irq(desc_data);
sysfs_remove_groups(desc_data->parent,
desc_data->chip_attr_groups);
}
mutex_destroy(&desc_data->mutex);