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

point trying to use the old boot sequence.  Replaced with a call to the
AoE demo code, so that people can at least build and try something useful.

elegant, but it works).

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).

This is the core portion of the async I/O interface.

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()).

these timer objects in AoE and UDP protocols (where there is no underlying
retransmission mechanism) without requiring each protocol to implement its
own individual retry logic.  Eventually, we should be able to use the same
timer code for TCP retransmissions as well.

  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.

orders of magnitude.

generic three-wire serial device support for EEPROM access.

hardware that can't autopad).

used on RTL8139 cards).

worrying about its stack being destroyed during the Etherboot run.

need for a CONFIG_RELOCATE.

install() now calls relocate(), moves the protected-mode code to the new
location, and calls hide_etherboot().

Change semantics; relocate() now just finds a suitable location; it
doesn't actually perform the relocation itself.  Code in libprefix does
the copy in flat real mode.

order?

requiring each caller to decide how many entries it wants to permit.

REAL_CODE() don't need it.

int13_boot() now does its own segment register save and restore, ready
for the removal of segment register restoration from the libkir
generic code.

Ignore carry flag for INT 15,88; the Ralf Brown interrupt list says
that CF is unreliable for this call.