Re: map gendisk (or blockdev) -> scsi_device

[Patrick Mansfield <patmans@us.ibm.com>]

On Wed, Jul 13, 2005 at 11:44:34AM -0700, Edward Falk wrote:
> 
> >You should revisit your code to not need access to the scsi_device
> >structure, and follow the layering of the block and scsi subsystems.
> 
> Maybe I should explain what I'm trying to do here.
> 
> Some of our software reads some of the values in /proc/ide/hda/.  We're 
> porting this facility to libata-based drivers in 2.6 and moving it to 
> /sysfs/block/sda/.  The sysfs show() functions will be given pointers to 
> gendisk structures but will need to obtain information from the 
> associated scsi_device structure.
> 
> Does anybody have any suggestions as to the "right" way to proceed?

Add or use the attributes under the scsi_device, then use the
/sysfs/block/sd/device symlink to find the corresponding scsi_device.

This is similar to what udev and lsscsi use to find device attributes.

udev uses libsysfs (included with udev).

[elm3b79 patman]$ ls -l /sys/block/sdo/device
lrwxrwxrwx    1 root     root            0 Jul 13 16:44 /sys/block/sdo/device -> ../../devices/pci0000:01/0000:01:0c.0/host2/rport-2:0-8/target2:0:8/2:0:8:0

[elm3b79 patman]$ ls /sys/block/sdo/device/
block   device_blocked  iodone_cnt     model        rescan      state vendor
bus     driver          ioerr_cnt      queue_depth  rev         timeout
delete  iocounterbits   iorequest_cnt  queue_type   scsi_level  type

-- Patrick Mansfield