Differential D16247 Diff 45219 share/man/man9/bus_dma.9

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share/man/man9/bus_dma.9

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	.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN			.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)			.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE			.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
	.\" POSSIBILITY OF SUCH DAMAGE.			.\" POSSIBILITY OF SUCH DAMAGE.
	.\"			.\"
	.\" $FreeBSD$			.\" $FreeBSD$
	.\" $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 July 17, 2013			.Dd July 12, 2018
	.Dt BUS_DMA 9			.Dt BUS_DMA 9
	.Os			.Os
	.Sh NAME			.Sh NAME
	.Nm bus_dma ,			.Nm bus_dma ,
	.Nm bus_dma_tag_create ,			.Nm bus_dma_tag_create ,
	.Nm bus_dma_tag_destroy ,			.Nm bus_dma_tag_destroy ,
	.Nm bus_dmamap_create ,			.Nm bus_dmamap_create ,
	.Nm bus_dmamap_destroy ,			.Nm bus_dmamap_destroy ,
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	May be			May be
	.Dv NULL .			.Dv NULL .
	.It Fa maxsize			.It Fa maxsize
	Maximum size, in bytes, of the sum of all segment lengths in a given			Maximum size, in bytes, of the sum of all segment lengths in a given
	DMA mapping associated with this tag.			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,			Even if your device has no restriction on the number of segments, passing a
	.Dv BUS_SPACE_UNRESTRICTED			maximal value is nonsensical.
				jhbUnsubmitted Not Done Inline Actions I actually view it is an API bug and would kind of document it as such, something like: "BUS_SPACE_UNRESTRICTED cannot be used with nsegments as it is instead interpreted as a very large segment count. For devices with no restriction on the number of segments should compute a reasonable number of segments for their DMA region." OTOH, I would actually like it if we had a non-terrible way to support BUS_SPACE_UNRESTRICTED such as clamping 'nsegments' at some value like 64, I just don't feel confident in picking that number. jhb: I actually view it is an API bug and would kind of document it as such, something like…
	may be specified.			.Nm
				will allocate
				.Fa nsegments
				worth of segments, even if they will not all be used.
				So users should compute a reasonable number of segments for their DMA region.
				bcrUnsubmitted Not Done Inline Actions I'd remove the "So" and just start the sentence with "Users should ..." bcr: I'd remove the "So" and just start the sentence with "Users should ..."
	.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
	.Fa dmat .			.Fa dmat .
	.It Fa flags			.It Fa flags
	Are as follows:			Are as follows:
	.Bl -tag -width ".Dv BUS_DMA_ALLOCNOW"			.Bl -tag -width ".Dv BUS_DMA_ALLOCNOW"
	.It Dv BUS_DMA_ALLOCNOW			.It Dv BUS_DMA_ALLOCNOW
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