[libvirt] [PATCH 6/8] Add unique_id to nodedev output

[John Ferlan]

On 06/11/2014 05:31 AM, Daniel P. Berrange wrote:
> On Tue, Jun 10, 2014 at 03:03:55PM -0400, John Ferlan wrote:
>> Add an optional unique_id parameter to nodedev.  Allows for easier lookup
>> and display of the unique_id value in order to document for use with
>> scsi_host code.
>>
>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>> ---
>>  docs/formatnode.html.in                            | 11 +++++++++++
>>  docs/schemas/nodedev.rng                           |  6 ++++++
>>  src/conf/node_device_conf.c                        | 23 ++++++++++++++++------
>>  src/conf/node_device_conf.h                        |  1 +
>>  src/node_device/node_device_linux_sysfs.c          |  6 ++++++
>>  src/test/test_driver.c                             |  5 +++--
>>  .../pci_8086_27c5_scsi_host_0_unique_id.xml        |  8 ++++++++
>>  tests/nodedevxml2xmltest.c                         |  1 +
>>  8 files changed, 53 insertions(+), 8 deletions(-)
>>  create mode 100644 tests/nodedevschemadata/pci_8086_27c5_scsi_host_0_unique_id.xml
>>
>> diff --git a/docs/formatnode.html.in b/docs/formatnode.html.in
>> index 76bf8af..cdf0277 100644
>> --- a/docs/formatnode.html.in
>> +++ b/docs/formatnode.html.in
>> @@ -173,6 +173,17 @@
>>              <dl>
>>                <dt><code>host</code></dt>
>>                <dd>The SCSI host number.</dd>
>> +              <dt><code>unique_id</code></dt>
>> +              <dd>On input, this optionally provides the value from the
>> +                'unique_id' file found in the scsi_host's directory. To
>> +                view the values of all 'unique_id' files, use <code>find -H
>> +                /sys/class/scsi_host/host{0..9}/unique_id |
>> +                xargs grep '[0-9]'</code>. On output, if the unique_id
>> +                file exists, the value from the file will be displayed.
>> +                This can be used in order to help uniquely identify the
>> +                scsi_host adapter in a <a href="formatstorage.html">
>> +                Storage Pool</a>. <span class="since">Since 1.2.6</span>
>> +              </dd>
> 
> Where is the data from the 'unique_id' coming from ? Is this since that
> Linux makes up, or is it some standard attribute from the hardware ? It
> would be desirable to document what it is in a way that's not simply
> refering to Linux sysfs, since sysfs itself is mostly undocumented :-)
> 
> 

Using 'unique_id' was from Osier's initial design - I 'assumed' that his
research into this had determined using this was unique enough.

A small amount of searching turns this up:

https://lkml.org/lkml/2011/8/17/274
...
+What:		/sys/bus/scsi/devices/host*/scsi_host/host*/unique_id
+Date:		February, 2003
+KernelVersion:	Unknown
+Contact:	James Bottomley <James.Bottomley at HansenPartnership.com>
+Description:
+		Read only unsigned integer uniquely identifying the SCSI host
+		within the system.  This value is assigned by the low level
+		driver.
+
...


Also from various sources, there's '/linux/include/scsi/scsi_host.h

/*
 * This is a unique identifier that must be assigned so that we
 * have some way of identifying each detected host adapter properly
 * and uniquely.  For hosts that do not support more than one card
 * in the system at one time, this does not need to be set.  It is
 * initialized to 0 in scsi_register.
 */
unsigned int unique_id;

> Regards,
> Daniel
>