Ralph Ronnquist:
...
> I think all mice are supposed to be handled by the kernel and will
> then get presented at /dev/input/mice
...

At some level every hardware is handled by the kernel. What you are
talking about is the input subsystem. To make a serial mouse work
or use the input subsystem you have to do an inputattach so the mouse
attached at /dev/ttySx is available as /dev/input/mouseY.

As you kan see in the kernel source/drivers/input/mouse/sermouse.c,
in function
static void sermouse_process_msc(struct sermouse *sermouse, signed char data)
it takes the protocol and converts it to another protocol.

For that function to work you need it be configured in the kernel,
build in or as a module. This command should return y or m.

# grep MOUSE_SERIAL /boot/config-`uname -r`
CONFIG_MOUSE_SERIAL=y

If done as a module, you need to
modprobe sermouse

After that you do the inputattach of the serial port.
At this stage you need to know the protocol used, there is no
autodetection.

It is in a sense similar to the gpm repeater mode.

> Section "ServerFlags"
>     Option "AutoAddDevices" "false"
> EndSection

I.e. either you do it all by yourself, or you use hw that can be auto
detected, there is no midpoint, like auto detect gpu and monitor, but
use this mouse...

Yea, thanks x devs. for ditching us with unusual hw.

> and b) installing xserver-xorg-input-kbd and xserver-xorg-input-mouse
...

Thoose two drivers are abandoned upstream from what I heard.

Regards,
/Karl Hammar