[PATCH v2 00/10] platform/chrome: Kunit tests and refactor for cros_ec_cmd_xfer()

[Tzung-Bi Shih <tzungbi@kernel.org>]

The 1st patch fixes an issue that cros_kunit_ec_xfer_mock() could return
garbage bytes for `msg->result` if the mock list is empty.

The 2nd ~ 6th patches add Kunit tests and refactors for cros_ec_cmd_xfer().

The last 4 patches change the behavior a bit by altering return codes.


Asynchronous mechanism in EC protocol:
EC returns EC_RES_IN_PROGRESS if the host command needs more time to
complete.  It saves the result into `saved_result` once the command
completed[1].

By design, AP should send another command EC_CMD_RESEND_RESPONSE for
getting the result from the previous pending command[2].  The mechanism
was only designed for commands that don't need responses[3].

However, the kernel code doesn't have such logic when dealing with
EC_RES_IN_PROGRESS.

The series doesn't fix it but leave it as is.  I doubt there is no existing
use case.

[1]: https://crrev.com/9b80051e01872d8cae86fff999b5d31a0bea985b/common/host_command.c#113
[2]: https://crrev.com/9b80051e01872d8cae86fff999b5d31a0bea985b/common/host_command.c#748
[3]: https://crrev.com/9b80051e01872d8cae86fff999b5d31a0bea985b/common/host_command.c#126


Return value overridden in cros_ec_send_command() if asynchronous:
By original intention, cros_ec_send_command() returns number of available
bytes of input payload.

When it falls into asynchronous path (i.e. EC_RES_IN_PROGRESS), both return
value and `msg->result` will be overridden by the subsequent
EC_CMD_GET_COMMS_STATUS.

The series doesn't fix it but leave it as is.

Tzung-Bi Shih (10):
  platform/chrome: cros_kunit_util: add default value for `msg->result`
  platform/chrome: cros_ec_proto: add "cros_ec_" prefix to
    send_command()
  platform/chrome: cros_ec_proto: add Kunit tests for cros_ec_cmd_xfer()
  platform/chrome: cros_ec_proto: add Kunit tests for
    cros_ec_send_command()
  platform/chrome: cros_ec_proto: separate cros_ec_xfer_command()
  platform/chrome: cros_ec_proto: separate cros_ec_wait_until_complete()
  platform/chrome: cros_ec_proto: change Kunit expectation when timed
    out
  platform/chrome: cros_ec_proto: return -EAGAIN when retries timed out
  platform/chrome: cros_ec_proto: add Kunit test for empty payload
  platform/chrome: cros_ec_proto: return -EPROTO if empty payload

 drivers/platform/chrome/cros_ec_proto.c      | 102 +++--
 drivers/platform/chrome/cros_ec_proto_test.c | 443 +++++++++++++++++++
 drivers/platform/chrome/cros_kunit_util.c    |  27 +-
 drivers/platform/chrome/cros_kunit_util.h    |   5 +
 4 files changed, 530 insertions(+), 47 deletions(-)

Changes from v1 (https://patchwork.kernel.org/project/chrome-platform/cover/20220628024913.1755292-1-tzungbi@kernel.org/):
- Drop "platform/chrome: cros_ec_proto: change Kunit expectation for EC errors"
  and "platform/chrome: cros_ec_proto: return standard error codes for EC
  errors" because they could break existing ABI.
- Add "platform/chrome: cros_kunit_util: add default value for `msg->result`".

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2.37.0.170.g444d1eabd0-goog