qemudriver: Support optional pre-start hook before spinning of the instance.

Signed-off-by: Joschka Seydell <joschka@seydell.org>

Author: JSydll

doc/configuration.rst

@@ -2867,6 +2867,10 @@ The QEMUDriver also requires the specification of:
   specify the build device tree
 - a path key, this is the path to the rootfs
 
+To allow interactions with the prepared, not yet started QEMU instance, the ``on()``
+method can take an optional ``pre_start_hook`` callable which is executed right before
+the CPU(s) are released.
+
 SigrokDriver
 ~~~~~~~~~~~~
 The :any:`SigrokDriver` uses a `SigrokDevice`_ resource to record samples and provides

labgrid/driver/qemudriver.py

@@ -259,9 +259,9 @@ def on_deactivate(self):
         shutil.rmtree(self._tempdir)
 
     @step()
-    def on(self):
-        """Start the QEMU subprocess, accept the unix socket connection and
-        afterwards start the emulator using a QMP Command"""
+    def on(self, pre_start_hook=None):
+        """Start the QEMU subprocess, accept the unix socket connection, run the
+        pre_start_hook if applicable and start the emulator using a QMP Command"""
         if self.status:
             return
         self.logger.debug("Starting with: %s", self._cmd)
@@ -289,6 +289,9 @@ def on(self):
         for v in self._forwarded_ports.values():
             self._add_port_forward(*v)
 
+        if pre_start_hook:
+            pre_start_hook()
+
         self.monitor_command("cont")
 
     @step()

tests/test_qemudriver.py

@@ -91,6 +91,18 @@ def test_qemu_on_off(qemu_target, qemu_driver, qemu_mock, qemu_version_mock):
 
     qemu_target.deactivate(qemu_driver)
 
+def test_qemu_on_pre_start_hook(qemu_target, qemu_driver, qemu_mock, qemu_version_mock):
+    qemu_target.activate(qemu_driver)
+    
+    called = False
+    def _hook():
+        nonlocal called
+        qemu_driver.monitor_command("info")
+        called = True
+
+    qemu_driver.on(pre_start_hook=_hook)
+    assert called
+
 def test_qemu_read_write(qemu_target, qemu_driver, qemu_mock, qemu_version_mock):
     qemu_target.activate(qemu_driver)