imsm: Allow to specify controller for --detail-platform.

imsm: Allow to specify controller for --detail-platform.

Usually, 'mdadm --detail-platform -e imsm' scans all the controllers
looking for IMSM capabilities. This patch provides the possibility
to specify a controller to scan, enabling custom usage by other
processes - especially with the --export switch.

$ mdadm --detail-platform
       Platform : Intel(R) Matrix Storage Manager
        Version : 9.5.0.1037
    RAID Levels : raid0 raid1 raid10 raid5
    Chunk Sizes : 4k 8k 16k 32k 64k 128k
    2TB volumes : supported
      2TB disks : not supported
      Max Disks : 7
    Max Volumes : 2 per array, 4 per controller
 I/O Controller : /sys/devices/pci0000:00/0000:00:1f.2 (SATA)

$ mdadm --detail-platform /sys/devices/pci0000:00/0000:00:1f.2
       Platform : Intel(R) Matrix Storage Manager
        Version : 9.5.0.1037
    RAID Levels : raid0 raid1 raid10 raid5
    Chunk Sizes : 4k 8k 16k 32k 64k 128k
    2TB volumes : supported
      2TB disks : not supported
      Max Disks : 7
    Max Volumes : 2 per array, 4 per controller
 I/O Controller : /sys/devices/pci0000:00/0000:00:1f.2 (SATA)

$ mdadm --detail-platform /sys/devices/pci0000:00/0000:00:1f.2 --export
MD_FIRMWARE_TYPE=imsm
IMSM_VERSION=9.5.0.1037
IMSM_SUPPORTED_RAID_LEVELS=raid0 raid1 raid10 raid5
IMSM_SUPPORTED_CHUNK_SIZES=4k 8k 16k 32k 64k 128k
IMSM_2TB_VOLUMES=yes
IMSM_2TB_DISKS=no
IMSM_MAX_DISKS=7
IMSM_MAX_VOLUMES_PER_ARRAY=2
IMSM_MAX_VOLUMES_PER_CONTROLLER=4

$ mdadm --detail-platform /sys/devices/pci0000:00/0000:00:1f.0 # This isn't an IMSM-capable controller
mdadm: no active Intel(R) RAID controller found under /sys/devices/pci0000:00/0000:00:1f.0

Signed-off-by: Maciej Naruszewicz <maciej.naruszewicz@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>