From: Bartosz Golaszewski Date: Fri, 4 Jul 2025 12:58:49 +0000 (+0200) Subject: gpio: sysfs: add a parallel class device for each GPIO chip using device IDs X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2028f854b3f5b3816cd5d5dd83057a873eddc4d6;p=thirdparty%2Fkernel%2Flinux.git gpio: sysfs: add a parallel class device for each GPIO chip using device IDs In order to enable moving away from the global GPIO numberspace-based exporting of lines over sysfs: add a parallel, per-chip entry under /sys/class/gpio/ for every registered GPIO chip, denoted by device ID in the file name and not its base GPIO number. Compared to the existing chip group: it does not contain the "base" attribute as the goal of this change is to not refer to GPIOs by their global number from user-space anymore. It also contains its own, per-chip export/unexport attribute pair which allow to export lines by their hardware offset within the chip. Caveat #1: the new device cannot be a link to (or be linked to by) the existing "gpiochip" entry as we cannot create links in /sys/class/xyz/. Caveat #2: the new entry cannot be named "gpiochipX" as it could conflict with devices whose base is statically defined to a low number. Let's go with "chipX" instead. While at it: the chip label is unique so update the untrue statement when extending the docs. Acked-by: Linus Walleij Link: https://lore.kernel.org/r/20250704-gpio-sysfs-chip-export-v4-2-9289d8758243@linaro.org Signed-off-by: Bartosz Golaszewski --- diff --git a/Documentation/ABI/obsolete/sysfs-gpio b/Documentation/ABI/obsolete/sysfs-gpio index 480316fee6d80..ff694708a3bef 100644 --- a/Documentation/ABI/obsolete/sysfs-gpio +++ b/Documentation/ABI/obsolete/sysfs-gpio @@ -25,8 +25,13 @@ Description: /active_low ... r/w as: 0, 1 /gpiochipN ... for each gpiochip; #N is its first GPIO /base ... (r/o) same as N - /label ... (r/o) descriptive, not necessarily unique + /label ... (r/o) descriptive chip name /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1) + /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 + /label ... (r/o) descriptive chip name + /ngpio ... (r/o) number of GPIOs exposed by the chip This ABI is obsoleted by Documentation/ABI/testing/gpio-cdev and will be removed after 2020. diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c index c4e85f2827697..990db0405cc86 100644 --- a/drivers/gpio/gpiolib-sysfs.c +++ b/drivers/gpio/gpiolib-sysfs.c @@ -45,6 +45,7 @@ struct gpiod_data { struct gpiodev_data { struct gpio_device *gdev; + struct device *cdev_id; /* Class device by GPIO device ID */ struct device *cdev_base; /* Class device by GPIO base */ }; @@ -399,6 +400,14 @@ static const struct attribute_group *gpio_groups[] = { * /base ... matching gpio_chip.base (N) * /label ... matching gpio_chip.label * /ngpio ... matching gpio_chip.ngpio + * + * AND + * + * /sys/class/gpio/chipX/ + * /export ... export GPIO at given offset + * /unexport ... unexport GPIO at given offset + * /label ... matching gpio_chip.label + * /ngpio ... matching gpio_chip.ngpio */ static ssize_t base_show(struct device *dev, struct device_attribute *attr, @@ -428,6 +437,111 @@ static ssize_t ngpio_show(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR_RO(ngpio); +static int export_gpio_desc(struct gpio_desc *desc) +{ + int offset, ret; + + CLASS(gpio_chip_guard, guard)(desc); + if (!guard.gc) + return -ENODEV; + + offset = gpio_chip_hwgpio(desc); + if (!gpiochip_line_is_valid(guard.gc, offset)) { + pr_debug_ratelimited("%s: GPIO %d masked\n", __func__, + gpio_chip_hwgpio(desc)); + return -EINVAL; + } + + /* + * No extra locking here; FLAG_SYSFS just signifies that the + * request and export were done by on behalf of userspace, so + * they may be undone on its behalf too. + */ + + ret = gpiod_request_user(desc, "sysfs"); + if (ret) + return ret; + + ret = gpiod_set_transitory(desc, false); + if (ret) { + gpiod_free(desc); + return ret; + } + + ret = gpiod_export(desc, true); + if (ret < 0) { + gpiod_free(desc); + } else { + set_bit(FLAG_SYSFS, &desc->flags); + gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_REQUESTED); + } + + return ret; +} + +static int unexport_gpio_desc(struct gpio_desc *desc) +{ + /* + * No extra locking here; FLAG_SYSFS just signifies that the + * request and export were done by on behalf of userspace, so + * they may be undone on its behalf too. + */ + if (!test_and_clear_bit(FLAG_SYSFS, &desc->flags)) + return -EINVAL; + + gpiod_unexport(desc); + gpiod_free(desc); + + return 0; +} + +static ssize_t do_chip_export_store(struct device *dev, + struct device_attribute *attr, + const char *buf, ssize_t size, + int (*handler)(struct gpio_desc *desc)) +{ + struct gpiodev_data *data = dev_get_drvdata(dev); + struct gpio_device *gdev = data->gdev; + struct gpio_desc *desc; + unsigned int gpio; + int ret; + + ret = kstrtouint(buf, 0, &gpio); + if (ret) + return ret; + + desc = gpio_device_get_desc(gdev, gpio); + if (IS_ERR(desc)) + return PTR_ERR(desc); + + ret = handler(desc); + if (ret) + return ret; + + return size; +} + +static ssize_t chip_export_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t size) +{ + return do_chip_export_store(dev, attr, buf, size, export_gpio_desc); +} + +static struct device_attribute dev_attr_export = __ATTR(export, 0200, NULL, + chip_export_store); + +static ssize_t chip_unexport_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t size) +{ + return do_chip_export_store(dev, attr, buf, size, unexport_gpio_desc); +} + +static struct device_attribute dev_attr_unexport = __ATTR(unexport, 0200, + NULL, + chip_unexport_store); + static struct attribute *gpiochip_attrs[] = { &dev_attr_base.attr, &dev_attr_label.attr, @@ -436,6 +550,15 @@ static struct attribute *gpiochip_attrs[] = { }; ATTRIBUTE_GROUPS(gpiochip); +static struct attribute *gpiochip_ext_attrs[] = { + &dev_attr_label.attr, + &dev_attr_ngpio.attr, + &dev_attr_export.attr, + &dev_attr_unexport.attr, + NULL +}; +ATTRIBUTE_GROUPS(gpiochip_ext); + /* * /sys/class/gpio/export ... write-only * integer N ... number of GPIO to export (full access) @@ -447,7 +570,7 @@ static ssize_t export_store(const struct class *class, const char *buf, size_t len) { struct gpio_desc *desc; - int status, offset; + int status; long gpio; status = kstrtol(buf, 0, &gpio); @@ -461,40 +584,7 @@ static ssize_t export_store(const struct class *class, return -EINVAL; } - CLASS(gpio_chip_guard, guard)(desc); - if (!guard.gc) - return -ENODEV; - - offset = gpio_chip_hwgpio(desc); - if (!gpiochip_line_is_valid(guard.gc, offset)) { - pr_debug_ratelimited("%s: GPIO %ld masked\n", __func__, gpio); - return -EINVAL; - } - - /* No extra locking here; FLAG_SYSFS just signifies that the - * request and export were done by on behalf of userspace, so - * they may be undone on its behalf too. - */ - - status = gpiod_request_user(desc, "sysfs"); - if (status) - goto done; - - status = gpiod_set_transitory(desc, false); - if (status) { - gpiod_free(desc); - goto done; - } - - status = gpiod_export(desc, true); - if (status < 0) { - gpiod_free(desc); - } else { - set_bit(FLAG_SYSFS, &desc->flags); - gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_REQUESTED); - } - -done: + status = export_gpio_desc(desc); if (status) pr_debug("%s: status %d\n", __func__, status); return status ? : len; @@ -511,7 +601,7 @@ static ssize_t unexport_store(const struct class *class, status = kstrtol(buf, 0, &gpio); if (status < 0) - goto done; + return status; desc = gpio_to_desc(gpio); /* reject bogus commands (gpiod_unexport() ignores them) */ @@ -520,18 +610,7 @@ static ssize_t unexport_store(const struct class *class, return -EINVAL; } - status = -EINVAL; - - /* No extra locking here; FLAG_SYSFS just signifies that the - * request and export were done by on behalf of userspace, so - * they may be undone on its behalf too. - */ - if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) { - gpiod_unexport(desc); - gpiod_free(desc); - status = 0; - } -done: + status = unexport_gpio_desc(desc); if (status) pr_debug("%s: status %d\n", __func__, status); return status ? : len; @@ -561,6 +640,11 @@ static int match_gdev(struct device *dev, const void *desc) static struct gpiodev_data * gdev_get_data(struct gpio_device *gdev) __must_hold(&sysfs_lock) { + /* + * Find the first device in GPIO class that matches. Whether that's + * the one indexed by GPIO base or device ID doesn't matter, it has + * the same address set as driver data. + */ struct device *cdev __free(put_device) = class_find_device(&gpio_class, NULL, gdev, match_gdev); @@ -787,6 +871,17 @@ int gpiochip_sysfs_register(struct gpio_device *gdev) return err; } + 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)) { + device_unregister(data->cdev_base); + err = PTR_ERR(data->cdev_id); + kfree(data); + return err; + } + return 0; } @@ -802,6 +897,7 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev) return; device_unregister(data->cdev_base); + device_unregister(data->cdev_id); kfree(data); }