Is ddb(4) over a USB-to-Serial port possible?

[Farhan Khan]

Hi all

I am reading here in section "10.5, On-Line Kernel Debugging User Remote 
GDB" that you can run ddb(4) over a serial cable. I am interested in 
setting this up.

My development box does not have a serial port (however, I do see a 
uart0 device in the kernel messages), so I attached a USB serial port 
attached to a machine with a serial port. The device uses the uslcom(4) 
driver and is listed as "Silicon Labs CP2102 USB to UART Bridge 
Controller". When I enter ddb and enter "gdb" I receive the error "The 
remote GDB backend could not be selected."

The hint.uart.0.port in /boot/device.hints is still set to 0x3F8, which 
corresponds to the aforementioned kernel messages. I am not certain if 
this is the same port as the USB-based serial port. Does this feature 
work over USB?

Thanks,
Farhan Khan