Re: [Qemu-devel] [PATCH 1/2] Add 'serial' attribute to virtio-blk devices

[Ryan Harper <ryanh@us.ibm.com>]

* Christoph Hellwig <hch@lst.de> [2010-06-21 07:46]:
> On Fri, Jun 18, 2010 at 01:38:02PM -0500, Ryan Harper wrote:
> > 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 NULL-terminated.  The buffer is also zero-padded
> > meaning that if the serial is 19 chars or less that we get a NULL terminated
> > string.  When copying this value into a string buffer, we must be careful to
> > copy up to the NULL (if it present) and only 20 if it is longer and not to
> > attempt to NULL terminate; this isn't needed.
> 
> Why is this virtio-blk specific?  In a later mail you mention you want
> to use it for udev.  So please export this from scsi/libata as well and
> we have one proper interface that we can use for all devices.

ATA and SCSI devices are already supported via ata_id and scsi_id
commands included in udev.  Qemu implements the drive serial part for
them and udev creates proper disk/by-id links.  This patch is about
filling the gap for virtio-blk devices which cannot work with ata_id and
scsi_id.


-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com