[RFC PATCH v3 11/18] ledtrig-blkdev: Add function to associate a device with an LED

[Ian Pilcher <arequipeno@gmail.com>]

If this is the first LED associated with the device, create the
/sys/block/<disk>/blkdev_leds directory.  Otherwise, increment its
reference count.

Create symlinks in /sys/class/leds/<led>/block_devices and
/sys/block/<disk>/blkdev_leds

If this the first device associated with any LED, schedule delayed work
to periodically check associated devices and blink LEDs

Signed-off-by: Ian Pilcher <arequipeno@gmail.com>
---
 drivers/leds/trigger/ledtrig-blkdev.c | 168 ++++++++++++++++++++++++++
 1 file changed, 168 insertions(+)

diff --git a/drivers/leds/trigger/ledtrig-blkdev.c b/drivers/leds/trigger/ledtrig-blkdev.c
index 2072cc904616..a1646752b9a0 100644
--- a/drivers/leds/trigger/ledtrig-blkdev.c
+++ b/drivers/leds/trigger/ledtrig-blkdev.c
@@ -312,3 +312,171 @@ void ledtrig_blkdev_disk_cleanup(struct gendisk *const gd)
 	mutex_unlock(&ledtrig_blkdev_mutex);
 }
 EXPORT_SYMBOL_GPL(ledtrig_blkdev_disk_cleanup);
+
+
+/*
+ *
+ *	Associate a block device with an LED
+ *
+ */
+
+/* Gets or allocs & initializes the blkdev disk for a gendisk */
+static int blkdev_get_disk(struct gendisk *const gd)
+{
+	struct ledtrig_blkdev_disk *disk;
+	struct kobject *dir;
+
+	if (gd->ledtrig != NULL) {
+		kobject_get(gd->ledtrig->dir);
+		return 0;
+	}
+
+	disk = kmalloc(sizeof(*disk), GFP_KERNEL);
+	if (disk == NULL)
+		return -ENOMEM;
+
+	dir = blkdev_mkdir("blkdev_leds", &disk_to_dev(gd)->kobj);
+	if (IS_ERR(dir)) {
+		kfree(disk);
+		return PTR_ERR(dir);
+	}
+
+	INIT_HLIST_HEAD(&disk->leds);
+	disk->gd = gd;
+	disk->dir = dir;
+	disk->read_ios = 0;
+	disk->write_ios = 0;
+
+	gd->ledtrig = disk;
+
+	return 0;
+}
+
+static void blkdev_put_disk(struct ledtrig_blkdev_disk *const disk)
+{
+	kobject_put(disk->dir);
+
+	if (hlist_empty(&disk->leds)) {
+		disk->gd->ledtrig = NULL;
+		kfree(disk);
+	}
+}
+
+static int blkdev_disk_add_locked(struct ledtrig_blkdev_led *const led,
+				  struct gendisk *const gd)
+{
+	struct ledtrig_blkdev_link *link;
+	struct ledtrig_blkdev_disk *disk;
+	unsigned long delay;
+	int ret;
+
+	link = kmalloc(sizeof(*link), GFP_KERNEL);
+	if (link == NULL) {
+		ret = -ENOMEM;
+		goto error_return;
+	}
+
+	ret = blkdev_get_disk(gd);
+	if (ret != 0)
+		goto error_free_link;
+
+	disk = gd->ledtrig;
+
+	ret = sysfs_create_link(disk->dir, &led->led_dev->dev->kobj,
+				led->led_dev->name);
+	if (ret != 0)
+		goto error_put_disk;
+
+	ret = sysfs_create_link(led->dir, &disk_to_dev(gd)->kobj,
+				gd->disk_name);
+	if (ret != 0)
+		goto error_remove_link;
+
+	link->disk = disk;
+	link->led = led;
+	hlist_add_head(&link->led_disks_node, &led->disks);
+	hlist_add_head(&link->disk_leds_node, &disk->leds);
+
+	if (ledtrig_blkdev_count == 0) {
+		delay = READ_ONCE(ledtrig_blkdev_interval);
+		WARN_ON(!schedule_delayed_work(&ledtrig_blkdev_work, delay));
+	}
+
+	++ledtrig_blkdev_count;
+
+	return 0;
+
+error_remove_link:
+	sysfs_remove_link(disk->dir, led->led_dev->name);
+error_put_disk:
+	blkdev_put_disk(disk);
+error_free_link:
+	kfree(link);
+error_return:
+	return ret;
+}
+
+static bool blkdev_already_linked(const struct ledtrig_blkdev_led *const led,
+				  const struct gendisk *const gd)
+{
+	const struct ledtrig_blkdev_link *link;
+
+	if (gd->ledtrig == NULL)
+		return false;
+
+	hlist_for_each_entry(link, &gd->ledtrig->leds, disk_leds_node) {
+
+		if (link->led == led) {
+			pr_info("blkdev LED: %s already associated with %s\n",
+				gd->disk_name, led->led_dev->name);
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static int blkdev_disk_add(struct ledtrig_blkdev_led *const led,
+			   const char *const disk_name, const size_t name_len)
+{
+	static char name[DISK_NAME_LEN];	/* only used w/ mutex locked */
+	struct gendisk *gd;
+	int ret;
+
+	if (name_len >= DISK_NAME_LEN) {
+		pr_info("blkdev LED: invalid device name %.*s\n",
+			(int)name_len, disk_name);
+		ret = -EINVAL;
+		goto exit_return;
+	}
+
+	ret = mutex_lock_interruptible(&ledtrig_blkdev_mutex);
+	if (ret != 0)
+		goto exit_return;
+
+	memcpy(name, disk_name, name_len);
+	name[name_len] = 0;
+	gd = get_disk_by_name(name);	/* increments disk's refcount */
+
+	if (gd == NULL) {
+		pr_info("blkdev LED: no such block device %.*s\n",
+			(int)name_len, disk_name);
+		ret = -ENODEV;
+		goto exit_unlock;
+	}
+
+	if (blkdev_already_linked(led, gd)) {
+		ret = -EEXIST;
+		goto exit_put_dev;
+	}
+
+	ret = blkdev_disk_add_locked(led, gd);
+
+exit_put_dev:
+	if (ret != 0)
+		put_device(disk_to_dev(gd));
+exit_unlock:
+	mutex_unlock(&ledtrig_blkdev_mutex);
+exit_return:
+	return ret;
+}
-- 
2.31.1