testing: serial: test-serial: use ioctls to enable/disable rs485

Using "serial.rs485" api, the "_set_rs485_mode" callback of serialposix
is not triggered when "rs485_mode" property is updated since its setter
is overridden, making the "serial.rs485" a self-standing emulation for rs485.

Since we already have a kernel emulation for half duplex rs485, we should
make use of it by calling the respective ioctls to enable/disable it when
required.

Explicitly call "_set_rs485_mode" by passing "serial.rs485.RS485Settings"
(enable) or None (disable) instead of setting this property.

Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com>

1 files changed, 20 insertions, 8 deletions

diff --git a/testing/serial/test-serial.py b/testing/serial/test-serial.py
index a36d5b6..8287e9c 100755
--- a/testing/serial/test-serial.py
+++ b/testing/serial/test-serial.py
@@ -18,6 +18,16 @@ def randomword(length):
     return "".join(random.choice(letters) for i in range(length))
 
 
+def set_rs485_mode(port, enable):
+    try:
+        port._set_rs485_mode(serial.rs485.RS485Settings() if enable else None)
+    except ValueError:
+        print(f"Port {port.port} does not support ioctl to enable/disable rs485")
+        # Continue as the serial port is assumed to be already prepared
+        # eg. using an USB to RS485 converter.
+        pass
+
+
 def transfer(tx, rx, size):
     # tx.reset_output_buffer()
     # rx.reset_input_buffer()
@@ -50,7 +60,11 @@ def update_serial_settings(tx, rx, baudrate, size):
 if __name__ == "__main__":
     parser = argparse.ArgumentParser()
     parser.add_argument("-b", "--baudrate", type=int, default=115200)
-    parser.add_argument("--rs485", action="store_true")
+    parser.add_argument(
+        "--rs485",
+        action="store_true",
+        help="Enable rs485 software emulation for half duplex rs485",
+    )
     parser.add_argument(
         "-s",
         "--size",
@@ -119,13 +133,11 @@ if __name__ == "__main__":
 
     args = parser.parse_args()
 
-    if args.rs485:
-        rx = serial.rs485.RS485(args.TX if args.reverse else args.RX)
-        tx = serial.rs485.RS485(args.RX if args.reverse else args.TX)
-        tx.rs485_mode = rx.rs485_mode = serial.rs485.RS485Settings()
-    else:
-        rx = serial.Serial(args.TX if args.reverse else args.RX)
-        tx = serial.Serial(args.RX if args.reverse else args.TX)
+    rx = serial.Serial(args.TX if args.reverse else args.RX)
+    tx = serial.Serial(args.RX if args.reverse else args.TX)
+
+    set_rs485_mode(tx, args.rs485)
+    set_rs485_mode(rx, args.rs485)
 
     size = args.size
     baudrate = args.baudrate