[PATCH v1] dts: add testpmd port information caching

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

When using port information multiple times in a testpmd shell instance
lifespan, it's desirable to not get the information each time, so
caching is added. In case the information changes, there's a way to
force the update with either TestPmdShell.show_port_info() or
TestPmdShell.show_port_info_all().

Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
---
 dts/framework/remote_session/testpmd_shell.py | 30 +++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/dts/framework/remote_session/testpmd_shell.py b/dts/framework/remote_session/testpmd_shell.py
index 43e9f56517..0a5cb385c9 100644
--- a/dts/framework/remote_session/testpmd_shell.py
+++ b/dts/framework/remote_session/testpmd_shell.py
@@ -586,6 +586,7 @@ class TestPmdShell(DPDKShell):
     """
 
     _app_params: TestPmdParams
+    _ports: list[TestPmdPort] | None
 
     #: The path to the testpmd executable.
     path: ClassVar[PurePath] = PurePath("app", "dpdk-testpmd")
@@ -618,6 +619,21 @@ def __init__(
             TestPmdParams(**app_params),
             name,
         )
+        self._ports = None
+
+    @property
+    def ports(self) -> list[TestPmdPort]:
+        """The ports of the instance.
+
+        This caches the ports returned by :meth:`show_port_info_all`.
+        To force an update of port information, execute :meth:`show_port_info_all` or
+        :meth:`show_port_info`.
+
+        Returns: The list of known testpmd ports.
+        """
+        if self._ports is None:
+            return self.show_port_info_all()
+        return self._ports
 
     def start(self, verify: bool = True) -> None:
         """Start packet forwarding with the current configuration.
@@ -747,7 +763,8 @@ def show_port_info_all(self) -> list[TestPmdPort]:
         # executed on a pseudo-terminal created by paramiko on the remote node, lines end with CRLF.
         # Therefore we also need to take the carriage return into account.
         iter = re.finditer(r"\*{21}.*?[\r\n]{4}", output + "\r\n", re.S)
-        return [TestPmdPort.parse(block.group(0)) for block in iter]
+        self._ports = [TestPmdPort.parse(block.group(0)) for block in iter]
+        return self._ports
 
     def show_port_info(self, port_id: int) -> TestPmdPort:
         """Returns the given port information.
@@ -765,7 +782,16 @@ def show_port_info(self, port_id: int) -> TestPmdPort:
         if output.startswith("Invalid port"):
             raise InteractiveCommandExecutionError("invalid port given")
 
-        return TestPmdPort.parse(output)
+        port = TestPmdPort.parse(output)
+        self._update_port(port)
+        return port
+
+    def _update_port(self, port: TestPmdPort) -> None:
+        if self._ports:
+            self._ports = [
+                existing_port if port.id != existing_port.id else port
+                for existing_port in self._ports
+            ]
 
     def show_port_stats_all(self) -> list[TestPmdPortStats]:
         """Returns the statistics of all the ports.
-- 
2.34.1