gpio: sysfs: remove the mockdev pointer from struct gpio_device

The usage of the mockdev pointer in struct gpio_device is limited to the
GPIO sysfs code. There's no reason to keep it in this top-level
structure. Create a separate structure containing the reference to the
GPIO device and the dummy class device that will be passed to
device_create_with_groups(). The !gdev->mockdev checks can be removed as
long as we make sure that all operations on the GPIO class are protected
with the sysfs lock.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250610-gpio-sysfs-chip-export-v1-6-a8c7aa4478b1@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index f23b4efea5905a9eab51ed9e50b5159135a8e26c..956411fc467a26a9827c616d8dc067c70f9244bf 100644 (file)
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -43,6 +43,11 @@ struct gpiod_data {
        bool direction_can_change;
 };
 
+struct gpiodev_data {
+       struct gpio_device *gdev;
+       struct device *cdev_base; /* Class device by GPIO base */
+};
+
 /*
  * Lock to serialise gpiod export and unexport, and prevent re-export of
  * gpiod whose chip is being unregistered.
@@ -399,27 +404,27 @@ static const struct attribute_group *gpio_groups[] = {
 static ssize_t base_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
 {
-       const struct gpio_device *gdev = dev_get_drvdata(dev);
+       const struct gpiodev_data *data = dev_get_drvdata(dev);
 
-       return sysfs_emit(buf, "%u\n", gdev->base);
+       return sysfs_emit(buf, "%u\n", data->gdev->base);
 }
 static DEVICE_ATTR_RO(base);
 
 static ssize_t label_show(struct device *dev, struct device_attribute *attr,
                          char *buf)
 {
-       const struct gpio_device *gdev = dev_get_drvdata(dev);
+       const struct gpiodev_data *data = dev_get_drvdata(dev);
 
-       return sysfs_emit(buf, "%s\n", gdev->label);
+       return sysfs_emit(buf, "%s\n", data->gdev->label);
 }
 static DEVICE_ATTR_RO(label);
 
 static ssize_t ngpio_show(struct device *dev, struct device_attribute *attr,
                          char *buf)
 {
-       const struct gpio_device *gdev = dev_get_drvdata(dev);
+       const struct gpiodev_data *data = dev_get_drvdata(dev);
 
-       return sysfs_emit(buf, "%u\n", gdev->ngpio);
+       return sysfs_emit(buf, "%u\n", data->gdev->ngpio);
 }
 static DEVICE_ATTR_RO(ngpio);
 
@@ -545,6 +550,26 @@ static const struct class gpio_class = {
        .class_groups = gpio_class_groups,
 };
 
+static int match_gdev(struct device *dev, const void *desc)
+{
+       struct gpiodev_data *data = dev_get_drvdata(dev);
+       const struct gpio_device *gdev = desc;
+
+       return data && data->gdev == gdev;
+}
+
+static struct gpiodev_data *
+gdev_get_data(struct gpio_device *gdev) __must_hold(&sysfs_lock)
+{
+       struct device *cdev __free(put_device) = class_find_device(&gpio_class,
+                                                                  NULL, gdev,
+                                                                  match_gdev);
+       if (!cdev)
+               return NULL;
+
+       return dev_get_drvdata(cdev);
+};
+
 /**
  * gpiod_export - export a GPIO through sysfs
  * @desc: GPIO to make available, already requested
@@ -590,12 +615,6 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 
        guard(mutex)(&sysfs_lock);
 
-       /* check if chip is being removed */
-       if (!gdev->mockdev) {
-               status = -ENODEV;
-               goto err_clear_bit;
-       }
-
        if (!test_bit(FLAG_REQUESTED, &desc->flags)) {
                gpiod_dbg(desc, "%s: unavailable (not requested)\n", __func__);
                status = -EPERM;
@@ -719,9 +738,9 @@ EXPORT_SYMBOL_GPL(gpiod_unexport);
 
 int gpiochip_sysfs_register(struct gpio_device *gdev)
 {
+       struct gpiodev_data *data;
        struct gpio_chip *chip;
        struct device *parent;
-       struct device *dev;
 
        /*
         * Many systems add gpio chips for SOC support very early,
@@ -747,32 +766,41 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
        else
                parent = &gdev->dev;
 
-       /* use chip->base for the ID; it's already known to be unique */
-       dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), gdev,
-                                       gpiochip_groups, GPIOCHIP_NAME "%d",
-                                       chip->base);
-       if (IS_ERR(dev))
-               return PTR_ERR(dev);
+       data = kmalloc(sizeof(*data), GFP_KERNEL);
+       if (!data)
+               return -ENOMEM;
+
+       data->gdev = gdev;
 
        guard(mutex)(&sysfs_lock);
-       gdev->mockdev = dev;
+
+       /* 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,
+                                                   gpiochip_groups,
+                                                   GPIOCHIP_NAME "%d",
+                                                   chip->base);
+       if (IS_ERR(data->cdev_base)) {
+               kfree(data);
+               return PTR_ERR(data->cdev_base);
+       }
 
        return 0;
 }
 
 void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 {
+       struct gpiodev_data *data;
        struct gpio_desc *desc;
        struct gpio_chip *chip;
 
        scoped_guard(mutex, &sysfs_lock) {
-               if (!gdev->mockdev)
+               data = gdev_get_data(gdev);
+               if (!data)
                        return;
 
-               device_unregister(gdev->mockdev);
-
-               /* prevent further gpiod exports */
-               gdev->mockdev = NULL;
+               device_unregister(data->cdev_base);
+               kfree(data);
        }
 
        guard(srcu)(&gdev->srcu);
@@ -798,9 +826,6 @@ static int gpiofind_sysfs_register(struct gpio_chip *gc, const void *data)
        struct gpio_device *gdev = gc->gpiodev;
        int ret;
 
-       if (gdev->mockdev)
-               return 0;
-
        ret = gpiochip_sysfs_register(gdev);
        if (ret)
                chip_err(gc, "failed to register the sysfs entry: %d\n", ret);

diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 58f64056de77b05e8cbcb2395a55da793b1a52fa..9b74738a9ca5b1a4826c8d56d871f8a7cf6ea1e7 100644 (file)
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -27,8 +27,6 @@
  * @dev: the GPIO device struct
  * @chrdev: character device for the GPIO device
  * @id: numerical ID number for the GPIO chip
- * @mockdev: class device used by the deprecated sysfs interface (may be
- * NULL)
  * @owner: helps prevent removal of modules exporting active GPIOs
  * @chip: pointer to the corresponding gpiochip, holding static
  * data for this device
@@ -65,7 +63,6 @@ struct gpio_device {
        struct device           dev;
        struct cdev             chrdev;
        int                     id;
-       struct device           *mockdev;
        struct module           *owner;
        struct gpio_chip __rcu  *chip;
        struct gpio_desc        *descs;