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bus_dma.9: Remove erroneous usage recommendation

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It is not valid to pass BUS_SPACE_UNRESTRICTED to bus_dma_tag_create()'s
nsegments parameter as it is interpreted as a very large segment count.
Subsequent allocation operations on the tag will preallocate some multiple of
that count.  BUS_SPACE_UNRESTRICTED therefore indicates something like:
malloc(infinity).

Discussed with:	bcr, jhb (earlier version)
This commit is contained in:
Conrad Meyer 2020-04-15 01:39:17 +00:00
parent e2b9919398
commit 102acd72aa
1 changed files with 1 additions and 4 deletions
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5
share/man/man9/bus_dma.9
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@ -53,7 +53,7 @@
.\" $FreeBSD$ .\" $FreeBSD$
.\" $NetBSD: bus_dma.9,v 1.25 2002/10/14 13:43:16 wiz Exp $ .\" $NetBSD: bus_dma.9,v 1.25 2002/10/14 13:43:16 wiz Exp $
.\" .\"
.Dd March 27, 2020 .Dd April 14, 2020
.Dt BUS_DMA 9 .Dt BUS_DMA 9
.Os .Os
.Sh NAME .Sh NAME
@ -618,9 +618,6 @@ DMA mapping associated with this tag.
.It Fa nsegments .It Fa nsegments
Number of discontinuities (scatter/gather segments) allowed Number of discontinuities (scatter/gather segments) allowed
in a DMA mapped region. in a DMA mapped region.
If there is no restriction,
.Dv BUS_SPACE_UNRESTRICTED
may be specified.
.It Fa maxsegsz .It Fa maxsegsz
Maximum size, in bytes, of a segment in any DMA mapped region associated Maximum size, in bytes, of a segment in any DMA mapped region associated
with with