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From:   Ian Pilcher <arequipeno@gmail.com>
To:     axboe@kernel.dk, pavel@ucw.cz
Cc:     linux-leds@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org,
        kabel@kernel.org
Subject: [PATCH v2 06/15] leds: trigger: blkdev: Add function to get gendisk by name
Date:   Thu,  9 Sep 2021 17:25:04 -0500
Message-Id: <20210909222513.2184795-7-arequipeno@gmail.com>
In-Reply-To: <20210909222513.2184795-1-arequipeno@gmail.com>
References: <20210909222513.2184795-1-arequipeno@gmail.com>
MIME-Version: 1.0
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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 <arequipeno@gmail.com>
---
 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;
+
+	return dev_to_disk(dev);
+}
+EXPORT_SYMBOL_NS_GPL(ledtrig_blkdev_get_disk, LEDTRIG_BLKDEV);
diff --git a/drivers/leds/trigger/ledtrig-blkdev.h b/drivers/leds/trigger/ledtrig-blkdev.h
index b1294da17ba3..a6ff24fad0c2 100644
--- a/drivers/leds/trigger/ledtrig-blkdev.h
+++ b/drivers/leds/trigger/ledtrig-blkdev.h
@@ -12,4 +12,7 @@
 extern struct mutex ledtrig_blkdev_mutex;
 extern void (*__ledtrig_blkdev_disk_cleanup)(struct gendisk *gd);
 
+/* Caller must call put_disk() */
+struct gendisk *ledtrig_blkdev_get_disk(const char *const name);
+
 #endif	/* __LEDTRIG_BLKDEV_H */
-- 
2.31.1