Subject: extent(9) feature.
To: None <firstname.lastname@example.org>
From: Paul Kranenburg <email@example.com>
Date: 09/01/1998 20:37:47
I propose to add an argument to extent_alloc_subregion() that allows
an arbitrary number to be specifed to which the start of the returned
region should be aligned.
extent_alloc_subregion(ex, substart, subend, size, alignment, skew,
boundary, flags, result)
(A) the result is aligned to `skew' modulo `aligment', i.e.
(result - skew) % alignment == 0
(B) `skew' is restricted to values smaller alignment:
0 <= skew < alignment (it follows: align==NOALIGN => skew==0)
(C) `size' + `skew' must not exceed the specified boundary:
size + skew <= boundary (applicable if boundary != NOBOUNDARY)
(D) obviously: if skew == 0 then there's no change to previous behaviour.
[In case you were wondering: I need this in some BUS DMA routines on
NetBSD/sparc to set up mappings between kernel/user virtual addresses
and DVMA addresses that are aligned with respect to the cache size
so cache coherency iron can do its job ].