Rework the read/write support in the bios disk driver some to cut down

on duplicated code and support 64-bit LBAs for GPT.
- The code to manage an EDD or C/H/S I/O request are now in their own
  routines.  The EDD routine now handles a full 64-bit LBA instead of
  truncating LBAs to the lower 32-bits.  (MBRs and BSD labels only
  have 32-bit LBAs anyway, so the only LBAs ever passed down were 32-bit).
- All of the bounce buffer and retry logic duplicated in bd_read() and
  bd_write() are merged into a single bd_io() routine that takes an
  extra direction argument.  bd_read() and bd_write() are now simple
  wrappers around bd_io().
- If a disk supports EDD then always use it rather than only using it if
  the cylinder is > 1023.  Other parts of the boot code already do
  something similar to this.  Also, GPT just uses LBAs, so for a GPT disk
  it's probably best to ignore C/H/S completely.  Always using EDD when
  it is supported by a disk is an easy way to accomplish this.

MFC after:	1 week

0 files changed, 0 insertions, 0 deletions