int lbs_cmd(struct cmd_ds_command *cmd,
            struct cmd_ds_command *resp,
            int resp_size,
            XXXPROPERTYPE callback);

caller would set
  cmd->command
  cmd->size
  cmd->(fields from union)
lbs_cmd() would set
  cmd->seqnum
  cmd->result = 0
  send to firmware
  it would block for if callback=0
  it would copy at most resp_size to *resp