Experimental Physics and
Industrial Control System

[email protected] · Mon, 11 Jul 94 13:35:51 -0500

> 
> 
> 
> I recently did device and driver support for the vmivme-2534 parallel
> i/o board.  This is a 32-bit board, and each 8-bit byte can be configured
> as either inputs or outputs.  In order to solve the immediate problem, I
> played Solomon and split the board right down the middle - 16 inputs and
> 16 outputs.
> 
> It turns out that this isn't really a very good solution - it would be
> much better if it were possible to allocate resources in a more flexible
> manner.
> 
> One possible solution would be to tweak the driver a bit and create 5
> device-support packages (32 bits in & no bits out, 8 bits in & 24 bits
> out, ... no bits in and & 32 bits out), but that seems kind of ugly.
> 
> The other options seem even uglier, and much more prone to error in the
> configuration process.
> 
> I'm probably missing the obvious here (now that's something I seem to excel
> at!).  Any ideas would be appreciated.

You could do the following:

The device init (NOT init_record) gets called twice at initialization time.
The second time is after all records have been initialized. As each record
calls the init_record entry of device support you could remember how each bit
is being referenced by the records (you get bitt offset and number of bits).
Then at the end configure the board. You can also look for conflicts and
generate errors.

Marty Kraimer

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System