test/py: Add a way to pass flags to sandbox

It is sometimes useful to restart sandbox with some particular flags to
test certain functionality. Add a new method to ConsoleSandbox to handle
this, without changing the existing APIs.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Acked-by: NStephen Warren <swarren@nvidia.com>

test/py/u_boot_console_sandbox.py

@@ -24,6 +24,7 @@ class ConsoleSandbox(ConsoleBase):
         """
 
         super(ConsoleSandbox, self).__init__(log, config, max_fifo_fill=1024)
+        self.sandbox_flags = []
 
     def get_spawn(self):
         """Connect to a fresh U-Boot instance.
@@ -51,8 +52,25 @@ class ConsoleSandbox(ConsoleBase):
             '-d',
             self.config.dtb
         ]
+        cmd += self.sandbox_flags
         return Spawn(cmd, cwd=self.config.source_dir)
 
+    def restart_uboot_with_flags(self, flags):
+        """Run U-Boot with the given command-line flags
+
+        Args:
+            flags: List of flags to pass, each a string
+
+        Returns:
+            A u_boot_spawn.Spawn object that is attached to U-Boot.
+        """
+
+        try:
+            self.sandbox_flags = flags
+            return self.restart_uboot()
+        finally:
+            self.sandbox_flags = []
+
     def kill(self, sig):
         """Send a specific Unix signal to the sandbox process.