This adds support to SCSI for enclosure services devices. It also makes
use of the enclosure services added in an earlier patch to display the
enclosure topology in sysfs.

At the moment, the enclosures are SAS specific, but if anyone actually
has a non-SAS enclosure that follows the SES-2 standard, we can add that
as well.

On my Vitesse based system, the enclosures show up like this:

sparkweed:~# ls -l /sys/class/enclosure/0\:0\:1\:0/
total 0
-r--r--r-- 1 root root 4096 2008-02-03 15:44 components
lrwxrwxrwx 1 root root    0 2008-02-03 15:44 device -> ../../../devices/pci0000:01/0000:01:02.0/host0/port-0:0/expander-0:0/port-0:0:12/end_device-0:0:12/target0:0:1/0:0:1:0
drwxr-xr-x 2 root root    0 2008-02-03 15:44 SLOT 000
drwxr-xr-x 2 root root    0 2008-02-03 15:44 SLOT 001
drwxr-xr-x 2 root root    0 2008-02-03 15:44 SLOT 002
drwxr-xr-x 2 root root    0 2008-02-03 15:44 SLOT 003
drwxr-xr-x 2 root root    0 2008-02-03 15:44 SLOT 004
drwxr-xr-x 2 root root    0 2008-02-03 15:44 SLOT 005
lrwxrwxrwx 1 root root    0 2008-02-03 15:44 subsystem -> ../../enclosure
--w------- 1 root root 4096 2008-02-03 15:44 uevent

And the individual occupied slots like this:

sparkweed:~# ls -l /sys/class/enclosure/0\:0\:1\:0/SLOT\ 001/
total 0
-rw-r--r-- 1 root root 4096 2008-02-03 15:45 active
lrwxrwxrwx 1 root root    0 2008-02-03 15:45 device -> ../../../../devices/pci0000:01/0000:01:02.0/host0/port-0:0/expander-0:0/port-0:0:11/end_device-0:0:11/target0:0:0/0:0:0:0
-rw-r--r-- 1 root root 4096 2008-02-03 15:45 fault
-rw-r--r-- 1 root root 4096 2008-02-03 15:45 locate
-rw-r--r-- 1 root root 4096 2008-02-03 15:45 status
lrwxrwxrwx 1 root root    0 2008-02-03 15:45 subsystem -> ../../../enclosure_component
-r--r--r-- 1 root root 4096 2008-02-03 15:45 type
--w------- 1 root root 4096 2008-02-03 15:45 uevent

You can flash the various blinky lights by echoing to the fault and locate files.

>From the device's point of view, you can see it has an enclosure like this:

sparkweed:~# ls /sys/class/scsi_disk/0\:0\:0\:0/device/
block:sda                     generic        queue_depth          state
bsg:0:0:0:0                   iocounterbits  queue_type           subsystem
bus                           iodone_cnt     rescan               timeout
delete                        ioerr_cnt      rev                  type
device_blocked                iorequest_cnt  scsi_device:0:0:0:0  uevent
driver                        modalias       scsi_disk:0:0:0:0    vendor
enclosure_component:SLOT 001  model          scsi_generic:sg0
evt_media_change              power          scsi_level

Note the enclosure_component:SLOT 001 which shows where in the enclosure
this device fits.

The astute will notice that I'm using SCSI VPD Inquiries to identify the
devices.  This, unfortunately, won't work for SATA devices unless we do
some really nasty hacking about on the SAT because the only think that
knows the SAS addresses for SATA devices is libsas, not libata where the
SAT resides.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>