In some cases, the virtual battery code creates
transactions that violate SB spec.
One example:
If the host command is structured as two messages -
a write to 0x03 (reg addr), followed by two bytes of write data,
the first byte of the second message (write data) will be sent to
virtual_battery_read(), as if it were a reg read request.
Let's do the following change for virtual battery:
1. Parse the command more carefully with state machines.
2. Support write caching for some critical registers.
3. Cache more attributes (0x03 and 0x0f).
BUG=chrome-os-partner:59239, chromium:659819
BRANCH=none
TEST='power_supply_info' works on kevin
Change-Id: Icdeb12b21f0dc3c329f29b206b7b9395ca4c9998
Reviewed-on: https://chromium-review.googlesource.com/407987
Commit-Ready: Philip Chen <philipchen@chromium.org>
Tested-by: Philip Chen <philipchen@chromium.org>
Reviewed-by: Shawn N <shawnn@chromium.org>
