Re: Replacing devices

[Thierry Bousch <bousch@topo.matups.fr>]

Hello Ulrich,

> While changing modm0dev to use the xdd feature of mint, I came across
> the following problem: this device driver disables the build-in stuff
> of tos, so /dev/modem1 does not work any longer, and it installs two
> new devices /dev/cua0 and /dev/ttyd0. But the biosfs does not allow
> to delete /dev/modem1, as it is a build-in bios device. Is there
> any possibility to get that done?

If you have programs which absolutely want to access /dev/modem1, just
rename the device to something else (modem1.old, say) and establish a
symbolic link between modem1 and the new device.

Accessing the old driver will always bring you into big trouble, but so
will the BIOS serial routines. And redirecting MiNT debugging to the
serial port won't work either, since it traps to the BIOS and modm0dev
has stolen the interrupt vectors. So it's hardly a filesystem issue;
modem1 will no longer work because it is the interface to the BIOS
system calls, and these calls no longer work.

Moreover, imagine a serial driver which only grabs the interrupt
vectors when it is opened (and restores them when it's closed). How
would you handle such a situation? How would you restore the /dev/modem1
device after you've deleted it?

So, the big question is: should BIOS calls still do something sensible
when a custom driver is installed? Personally, I couldn't care less
about this, and it's not a trivial problem anyway...

Thierry.