stack or INT 13 emulator etc.

period before updating to the new driver API (which can cope with
having TX packets in progress).

(This actually matters once you try using TCP, because you *will*
receive full-sized frames.)

Update rtl8139 driver to instantiate an SPI interface with a three-wire
device attached.

(since SPI bit-bashing will require different delay semantics).

Print warning message at probe time.

not-yet-updated drivers to at least function.

layer asynchronous, so keeping the sync/async boundary within aoedev.c
seems cleanest for now.

async_wait(), though we may wish to move this higher up the stack, and
consider making the block device model asynchronous.  (There is only a
marginal cost for synchronous devices, since they can simply call
async_done() before returning; async_wait() will work seamlessly in this
situation).

Removed data_in_len and data_out_len from ata_command structure; the
lengths are implied by the sector count and the presence of the data_in
or data_out pointers.

Changed AoE code to use subcommands by default, and made aoe_issue()
nonblocking (with completion via async_wait()).

  Cannot yet handle reads of more than two sectors

  No retransmission

  No way to find out a target's MAC address (this proof of concept uses
  broadcasts)

These limitations shall not last long!  :)

Increase code simplicity at the expense of around 64 bytes.

generic three-wire serial device support for EEPROM access.