For compatibility with other software raid environments an isci [1]
device may contain up to two controller instances per pci device.
Currently the sysfs path for its scsi_host objects is:
../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host10/scsi_host/host10
../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host11/scsi_host/host11
But to reflect reality the pci device is actually the parent of two
independent controller instances. With a mockup like:
../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/controller0/host10/scsi_host/host10
../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/controller1/host11/scsi_host/host11
I can see this being beneficial in a few ways:
1/ fix dev_printk() messages which right now give an ambiguous "isci
0000:03:00.0" prefix
2/ controller boundaries are visible via the sysfs path without need to
to look at sas_addresses to determine the controller.
2/ if we ever wanted to support some per controller attributes between
the global pci attributes and the scsi_host attributes.
...but would this confuse /dev/disk/by-path/ or any other unintended
side effects?
--
Dan
[1]: http://marc.info/?l=linux-scsi&m=129703780424729&w=2
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