Should we also use the functions in the devices.c to implement all functions on devices like ioctls etc.?
for the other int21 (disk read/write for instance), yes ioctl are the way to go
I don't quite understand your english here, are you saying that ioctls in int21 _should_ be implemented using functions from devices.c (like DOSDEV_IoctlRead/DOSDEV_IoctlWrite)?
nog.