asy should not adjust line control or speed on attach
asy driver exposes each
COM port in an x86 system for use by usermode software (e.g. login sessions, etc). On attach, the driver resets some of control registers for each UART to default values; e.g. 9600 baud, 8 bit words, etc.
This is problematic as the values chosen for the reset are hard-coded, and may not match up with the
tty*-mode boot options. If single-stepping through the
asy attach routine with
kmdb, it's possible that the console (which may not be operating at 9600 baud) will become inaccessible during this initialisation, bringing the system to rest.
Presumably the bootloader (e.g.
grub) will, in a system with a serial console, configure the UART to the correct operating settings for early boot. The
ttymon service will configure any serial ports used for login to the correct settings. The console subsystem itself likely does some early configuration based on the boot arguments. Needless to say there are probably enough cooks in this kitchen already, and
asy should only be reconfiguring the UART in the event that somebody opens an
asy device node.