MFC r237452:

MFC r237452:

  r237452 | ken | 2012-06-22 12:57:06 -0600 (Fri, 22 Jun 2012) | 25 lines

  Change 'camcontrol defects' to first probe a drive to find out how much
  defect information it has before grabbing the full defect list.

  This works around a bug with some Hitachi drives that generate data overrun
  errors when they are asked for more defect data than they have.

  The change is done in a spec-compliant way, so it should have no negative
  impact on drives that don't have this issue.

  This is based on work originally done at Sandvine.

  scsi_da.h:	Add a define for the maximum amount of data that can be
  		contained in a defect list.

  camcontrol.c:	Update the readdefects() function to issue an initial
  		command to determine the length of the defect list, and
  		then use that length in the request for the full defect
  		list.

  camcontrol.8:	Add a note that some drives will report 0 defects available
  		if you don't request either the PLIST or GLIST.

  Submitted by:	Mark Johnston <markjdb@gmail.com> (original version)

git-svn-id: svn://svn.freebsd.org/base/stable/9@237828 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f