[SCSI] genhd: add a new attribute "alias" in gendisk

This patch allows the user to set an "alias" of the disk via sysfs interface.

This patch only adds a new attribute "alias" in gendisk structure.
To show the alias instead of the device name in kernel messages,
we need to revise printk messages and use alias_name() in them.

Example:
(current) printk("disk name is %s\n", disk->disk_name);
(new)     printk("disk name is %s\n", alias_name(disk));

Users can use alphabets, numbers, '-' and '_' in "alias" attribute. A disk can
have an "alias" which length is up to 255 bytes. This attribute is write-once.

Suggested-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Suggested-by: Jon Masters <jcm@redhat.com>
Signed-off-by: Nao Nishijima <nao.nishijima.xt@hitachi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index c1eb41c..2b5d561 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -206,3 +206,16 @@ Description:
 		when a discarded area is read the discard_zeroes_data
 		parameter will be set to one. Otherwise it will be 0 and
 		the result of reading a discarded area is undefined.
+What:		/sys/block/<disk>/alias
+Date:		Aug 2011
+Contact:	Nao Nishijima <nao.nishijima.xt@hitachi.com>
+Description:
+		A raw device name of a disk does not always point a same disk
+		each boot-up time. Therefore, users have to use persistent
+		device names, which udev creates when the kernel finds a disk,
+		instead of raw device name. However, kernel doesn't show those
+		persistent names on its messages (e.g. dmesg).
+		This file can store an alias of the disk and it would be
+		appeared in kernel messages if it is set. A disk can have an
+		alias which length is up to 255bytes. Users can use alphabets,
+		numbers, "-" and "_" in alias name. This file is writeonce.