V68 - what does disjointio do?

[Michael DeCorte]

Hello,

I hope someone can help me with a problem I have been having.  I am
modifying a tape driver for V68 (Motorola's SysV.3 for 680x0's).

After reading the code I am left with a few questions.

The code uses disjointio but I can't find any docs on it.  as best as
I can tell I you pass it an memory location of an object the size of
the object and an array that gets filled up with the real address for
each fragment of the object.  But I don't know if there are any side
affects.  I assume that it will pull in any pages that aren't in real
memory off of disk but does it lock them?  If it does how do they get
unlocked?  You see I can't find any place where the memory pages are
getting locked or unlocked.

If disjointio doesn't do the locking who does?  I have some ATT docs
that say dma_breakup can do it but these same doecs say "If your
device has special hardware for performing scatter-gather transfers
you should not use this routine."  Well I have scatter-gather
transfers and if my guess is correct using dma_breakup will give me a
very large penalty. 

"Writing a Unix device driver" says I should use vslock and vsunlock
but I don't have these routines. (I checked with nm).

So if you know what disjointio does or how to lock or unlock page or
what manual/book/whatever documents this stuff please drop be a note.

thanks


--

Michael DeCorte // (215)546-0497 // 2300 Naudain St. "H", Phil, PA 19146
Internet: mrd at sun.soe.clarkson.edu  // Bitnet:   mrd at clutx.bitnet        
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