Experimental Physics and
Industrial Control System

[email protected] (Bill Brown) · Tue, 12 Jul 94 15:06:26 PDT

I want to do a little "thinking out loud" here .

You said:
> 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.

This implies that the dev init routine has to know about some hardware
stuff.  Well, maybe not.  Perhaps all that's needed is to add one entry
point in the driver stuff that expects a board #, a byte #, and a direction
(in or out) indicator to finally initialize the hardware.

But, since ioScan needs to know inputs from outputs, the logical place for
the direction information is in the driver control structures.  devSupport
needs an entry point in the driver to call to get the address of the 
structures so it can use them during dev_Init.  But it really doesn't need
to know about the structure; all it needs is a pointer to the location
that has the direction information about the specified i/o board.

One more question - is there any defined limit on the size of a mbb[io]
PV?  Since it seems like they may overlap byte boundries, this could get
tricky.  The only _real_ problem I see the slight time-offset in the output/
input values which could result if the mbb[io] PV spans byte boundaries.

-bill

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System