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.TH "SA1100_START_DMA" "" "06 October 2005" "" ""

.SH NAME
sa1100_start_dma \- submit a data buffer for DMA
.SH SYNOPSIS
"SYNOPSIS"
.sp
\fB
.sp
int sa1100_start_dma  (dma_regs_t * \fIregs\fB, dma_addr_t \fIdma_ptr\fB, u_int \fIsize\fB);
\fR
.SH "ARGUMENTS"
.TP
\fB\fIregs\fB\fR
identifier for the channel to use
.TP
\fB\fIdma_ptr\fB\fR
buffer physical (or bus) start address
.TP
\fB\fIsize\fB\fR
buffer size
.SH "DESCRIPTION"
.PP
This function hands the given data buffer to the hardware for DMA
access. If another buffer is already in flight then this buffer
will be queued so the DMA engine will switch to it automatically
when the previous one is done.  The DMA engine is actually toggling
between two buffers so at most 2 successful calls can be made before
one of them terminates and the callback function is called.
.PP
The \fIregs\fR identifier is provided by a successful call to
\fBsa1100_request_dma\fR\&.
.PP
The \fIsize\fR must not be larger than MAX_DMA_SIZE\&.  If a given buffer
is larger than that then it's the caller's responsibility to split
it into smaller chunks and submit them separately. If this is the
case then a \fIsize\fR of CUT_DMA_SIZE is recommended to avoid ending
up with too small chunks. The callback function can be used to chain
submissions of buffer chunks.
.SH "ERROR RETURN VALUES"
.PP
-EOVERFLOW: Given buffer size is too big.
-EBUSY: Both DMA buffers are already in use.
-EAGAIN: Both buffers were busy but one of them just completed
but the interrupt handler has to execute first.
.PP
This function returs 0 on success.