Re: Interface for communicating from kernel to user mode

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	Hello.  Depending on the amount of data yu want to pass between kernel space and user
space, you might consider writing a simple device driver kernel module which implements ioctl(2) 
functions or read(2) and write(2) functionality.  Ioctl commands are good for passing data in chunks 
of less than 256 bytes in either direction and read/write functions can move arbitrary amounts of 
data between kernel and user space.  Depending on how your current linux user space code works,
this might give yu the ability to provide the same functionality in NetBSD that linux provides
from the user space program's perspective.  Kernel modules don't have to be complex, it's
better if they're not, and they give you a lot of flexibility about how you want to interface
with the kernel.  Using a module also lets yu develop your interface without having to touch as
many other kernel source files.  While it's true you would need to recompile your module for
kernel updates, the basic API's for dealing with ioctls and read/write calls have been stable
in NetBSD for many years.  I recently migrated a module from NetBSD-5, for example, to
NetBSD-current, and the code changes required to make it work were very few and only took me an
hour or so to make and test.  that's not bad for such a large jump in version.

Just a thought.

-thanks
-Brian