I have an old hppa workstation install Openbsd on it,suppose
i want to use bktr driver on it,i see bktr is configured on some archs(amd64,i386,ppc) but not on hppa,can i use
the bktr driver line from amd64 or i386 in Generic kernel or custom kernel config?
You can always try to build a kernel with it, but I doubt it will work. If it did, it'd be part of the GENERIC config.
Also, note that the bktr driver appears to be an i2c master. You'd need iic(4) on hppa (I'm not familiar with the architecture, just mentioning it).
Regards,
Alister
Very bad 
I have build today a kernel for hppa,with driver re0(d-link)
taken from another config
All works fine..in this case