UBootDriver: add strip_timestamp option

Some U-Boot configurations may prepend timestamps to the beginning of
every line during early boot, and at the prompt, e.g.:

|[   2.397] Failed to get fastboot key config: -19
|[   2.402] sdh@d4280000: 74 clk wait timeout(100)
|[   2.405] MMC: no card present
|[   2.408] mmc_init: -123, time 7
|[   2.412] Net:   RGMII interface
|[   2.414] eth0: ethernet@cac80000
|[   2.420] Autoboot in 5 seconds
|=>
|=> [   4.878] <INTERRUPT>
|=> [   5.920] <INTERRUPT>
|=> [ 503.743] d<INTERRUPT>
|=> [ 505.712]  <INTERRUPT>

Unfortunately, this means that strategies may not behave as expected
when trying to run commands, as labgrid's console.expect() function will
always find the timestamp in addition to the check strings it sends.
Handle this by adding a strip_timestamp boolean option to the
UBootDriver, which if enabled strips timestamps from received lines when
found.

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>

Author: threexc

labgrid/driver/ubootdriver.py

@@ -1,14 +1,16 @@
 """The U-Boot Module contains the UBootDriver"""
+import re
 import attr
 from pexpect import TIMEOUT
 
 from ..factory import target_factory
 from ..protocol import CommandProtocol, ConsoleProtocol, LinuxBootProtocol
-from ..util import gen_marker, Timeout, re_vt100
+from ..util import gen_marker, re_vt100, Timeout
 from ..step import step
 from .common import Driver
 from .commandmixin import CommandMixin
 
+re_uboot_timestamp = re.compile(r"^\[\s+\d+\.\d+\]\s*")
 
 @target_factory.reg_driver
 @attr.s(eq=False)
@@ -28,6 +30,7 @@ class UBootDriver(CommandMixin, Driver, CommandProtocol, LinuxBootProtocol):
         boot_command (str): optional boot command to boot target
         login_timeout (int): optional, timeout for login prompt detection
         boot_timeout (int): optional, timeout for initial Linux Kernel version detection
+        strip_timestamp (bool, default=False): strip timestamps prepended to console when present
 
     """
     bindings = {"console": ConsoleProtocol, }
@@ -43,6 +46,7 @@ class UBootDriver(CommandMixin, Driver, CommandProtocol, LinuxBootProtocol):
     boot_commands = attr.ib(default=attr.Factory(dict), validator=attr.validators.instance_of(dict))
     login_timeout = attr.ib(default=30, validator=attr.validators.instance_of(int))
     boot_timeout = attr.ib(default=30, validator=attr.validators.instance_of(int))
+    strip_timestamp = attr.ib(default=False, validator=attr.validators.instance_of(bool))
 
     def __attrs_post_init__(self):
         super().__attrs_post_init__()
@@ -79,6 +83,11 @@ def _run(self, cmd: str, *, timeout: int = 30, codec: str = "utf-8", decodeerror
             data = re_vt100.sub(
                 '', before.decode('utf-8'), count=1000000
             ).replace("\r", "").split("\n")
+
+            # Strip possible U-Boot timestamps from the line
+            if self.strip_timestamp:
+                data = [re_uboot_timestamp.sub('', line) for line in data]
+
             self.logger.debug("Received Data: %s", data)
             # Remove first element, the invoked cmd
             data = data[data.index(marker) + 1:]