From a5eb9e4ff18a33e43557d44b205f953b0c1efade Mon Sep 17 00:00:00 2001 From: Ryan Harper Date: Wed, 23 Jun 2010 22:19:57 -0500 Subject: [PATCH] virtio_blk: Add 'serial' attribute to virtio-blk devices (v2) Create a new attribute for virtio-blk devices that will fetch the serial number of the block device. This attribute can be used by udev to create disk/by-id symlinks for devices that don't have a UUID (filesystem) associated with them. ATA_IDENTIFY strings are special in that they can be up to 20 chars long and aren't required to be nul-terminated. The buffer is also zero-padded meaning that if the serial is 19 chars or less that we get a nul-terminated string. When copying this value into a string buffer, we must be careful to copy up to the nul (if it present) and only 20 if it is longer and not to attempt to nul terminate; this isn't needed. Changes since v1: - Added BUILD_BUG_ON() for PAGE_SIZE check - Removed min() since BUILD_BUG_ON() handles the check - Replaced serial_sysfs() by copying id directly to buffer Signed-off-by: Ryan Harper Signed-off-by: john cooper Signed-off-by: Rusty Russell --- drivers/block/virtio_blk.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 2d6191aa5948..7a93b3f68849 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -281,6 +281,27 @@ static int index_to_minor(int index) return index << PART_BITS; } +static ssize_t virtblk_serial_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct gendisk *disk = dev_to_disk(dev); + int err; + + /* sysfs gives us a PAGE_SIZE buffer */ + BUILD_BUG_ON(PAGE_SIZE < VIRTIO_BLK_ID_BYTES); + + buf[VIRTIO_BLK_ID_BYTES] = '\0'; + err = virtblk_get_id(disk, buf); + if (!err) + return strlen(buf); + + if (err == -EIO) /* Unsupported? Make it empty. */ + return 0; + + return err; +} +DEVICE_ATTR(serial, S_IRUGO, virtblk_serial_show, NULL); + static int __devinit virtblk_probe(struct virtio_device *vdev) { struct virtio_blk *vblk; @@ -465,8 +486,15 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) add_disk(vblk->disk); + err = device_create_file(disk_to_dev(vblk->disk), &dev_attr_serial); + if (err) + goto out_del_disk; + return 0; +out_del_disk: + del_gendisk(vblk->disk); + blk_cleanup_queue(vblk->disk->queue); out_put_disk: put_disk(vblk->disk); out_mempool: -- 2.39.5