Add ledtrig_blkdev_get_disk() to find block device by name and increment
its reference count.  (Caller must call put_disk().)  Must be built-in to
access block_class and disk_type symbols.

Signed-off-by: Ian Pilcher <redacted>
---
 drivers/leds/trigger/ledtrig-blkdev-core.c | 20 ++++++++++++++++++++
 drivers/leds/trigger/ledtrig-blkdev.h      |  3 +++
 2 files changed, 23 insertions(+)

diff --git a/drivers/leds/trigger/ledtrig-blkdev-core.c b/drivers/leds/trigger/ledtrig-blkdev-core.c
index d7b02e760b06..5fd741aa14a6 100644
--- a/drivers/leds/trigger/ledtrig-blkdev-core.c
+++ b/drivers/leds/trigger/ledtrig-blkdev-core.c

@@ -33,3 +33,23 @@ void ledtrig_blkdev_disk_cleanup(struct gendisk *const gd)
 
 	mutex_unlock(&ledtrig_blkdev_mutex);
 }
+
+/* class_find_device() callback.  Must be built-in to access disk_type. */
+static int blkdev_match_name(struct device *const dev, const void *const name)
+{
+	return dev->type == &disk_type
+			&& sysfs_streq(dev_to_disk(dev)->disk_name, name);
+}
+
+/* Must be built-in to access block_class */
+struct gendisk *ledtrig_blkdev_get_disk(const char *const name)
+{
+	struct device *dev;
+
+	dev = class_find_device(&block_class, NULL, name, blkdev_match_name);
+	if (dev == NULL)
+		return NULL;