console: T2529: migrate from ttyUSB device to new device in /dev/serial/by-bus

During testing it was discovered that there is a well known problem (we had for
ethernet interfaces) also in the serial port world. They will be enumerated and
mapped to /dev/ttyUSBxxx differently from boot to boot. This is especially
painful on my development APU4 board which also has a Sierra Wireless MC7710
LTE module installed.

The serial port will toggle between ttyUSB2 and ttyUSB5 depending on the
amount of serial port extenders attached (FT4232H).

The shipped udev rule (/usr/lib/udev/rules.d/60-serial.rules) partly solves
this by enumerating the devices into /dev/serial/by-id folder with their name
and serial number - it's a very good idea but I've found that not all of the
FT4232H dongles have a serial number programmed - this leads to the situation
that when you plug in two cables with both having serial number 0 - only one
device symlink will appear - the previous one is always overwritten by the
latter one.

Derive /usr/lib/udev/rules.d/60-serial.rules and create a /dev/serial/by-bus
directory and group devices by attached USB root port.

1 files changed, 20 insertions, 0 deletions

diff --git a/src/migration-scripts/system/16-to-17 b/src/migration-scripts/system/16-to-17
index ca3b10f49..981149d1b 100755
--- a/src/migration-scripts/system/16-to-17
+++ b/src/migration-scripts/system/16-to-17
@@ -47,6 +47,26 @@ else:
         if config.exists(dev_path + ['modem']):
             config.delete(dev_path + ['modem'])
 
+        # Only continue on USB based serial consoles
+        if not 'ttyUSB' in device:
+            continue
+
+        # A serial console has been configured but it does no longer
+        # exist on the system - cleanup
+        if not os.path.exists(f'/dev/{device}'):
+            config.delete(dev_path)
+            continue
+
+        # migrate from ttyUSB device to new device in /dev/serial/by-bus
+        for root, dirs, files in os.walk('/dev/serial/by-bus'):
+            for usb_device in files:
+                device_file = os.path.realpath(os.path.join(root, usb_device))
+                # migrate to new USB device names (T2529)
+                if os.path.basename(device_file) == device:
+                    config.copy(dev_path, base + ['device', usb_device])
+                    # Delete old USB node from config
+                    config.delete(dev_path)
+
     try:
         with open(file_name, 'w') as f:
             f.write(config.to_string())