iio: core: move to cleanup.h magic

Use the new cleanup magic for handling mutexes in IIO. This allows us to
greatly simplify some code paths.

Note that we keep the plain mutex calls in the
iio_device_release|acquire() APIs since in there the macros would likely
not help much (as we want to keep the lock acquired when he leave the
APIs).
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240229-iio-use-cleanup-magic-v3-1-c3d34889ae3c@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -11,6 +11,7 @@
 
 #include <linux/anon_inodes.h>
 #include <linux/cdev.h>
+#include <linux/cleanup.h>
 #include <linux/debugfs.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -1810,31 +1811,24 @@ static long iio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	struct iio_dev *indio_dev = ib->indio_dev;
 	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 	struct iio_ioctl_handler *h;
-	int ret = -ENODEV;
-
-	mutex_lock(&iio_dev_opaque->info_exist_lock);
+	int ret;
 
+	guard(mutex)(&iio_dev_opaque->info_exist_lock);
 	/*
 	 * The NULL check here is required to prevent crashing when a device
 	 * is being removed while userspace would still have open file handles
 	 * to try to access this device.
 	 */
 	if (!indio_dev->info)
-		goto out_unlock;
+		return -ENODEV;
 
 	list_for_each_entry(h, &iio_dev_opaque->ioctl_handlers, entry) {
 		ret = h->ioctl(indio_dev, filp, cmd, arg);
 		if (ret != IIO_IOCTL_UNHANDLED)
-			break;
+			return ret;
 	}
 
-	if (ret == IIO_IOCTL_UNHANDLED)
-		ret = -ENODEV;
-
-out_unlock:
-	mutex_unlock(&iio_dev_opaque->info_exist_lock);
-
-	return ret;
+	return -ENODEV;
 }
 
 static const struct file_operations iio_buffer_fileops = {
@@ -2062,8 +2056,7 @@ void iio_device_unregister(struct iio_dev *indio_dev)
 
 	cdev_device_del(&iio_dev_opaque->chrdev, &indio_dev->dev);
 
-	mutex_lock(&iio_dev_opaque->info_exist_lock);
-
+	scoped_guard(mutex, &iio_dev_opaque->info_exist_lock) {
 		iio_device_unregister_debugfs(indio_dev);
 
 		iio_disable_all_buffers(indio_dev);
@@ -2072,8 +2065,7 @@ void iio_device_unregister(struct iio_dev *indio_dev)
 
 		iio_device_wakeup_eventset(indio_dev);
 		iio_buffer_wakeup_poll(indio_dev);
-
-	mutex_unlock(&iio_dev_opaque->info_exist_lock);
+	}
 
 	iio_buffers_free_sysfs_and_mask(indio_dev);
 }