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.TH "USB_BUFFER_ALLOC" "9" "17 July 2003" "" ""

.SH NAME
usb_buffer_alloc \- allocate dma-consistent buffer for URB_NO_xxx_DMA_MAP
.SH SYNOPSIS
.sp
\fB
.sp
void * usb_buffer_alloc  (struct usb_device * \fIdev\fB, size_t \fIsize\fB, int \fImem_flags\fB, dma_addr_t * \fIdma\fB);
\fR
.SH "ARGUMENTS"
.TP
\fB\fIdev\fB\fR
device the buffer will be used with
.TP
\fB\fIsize\fB\fR
requested buffer size
.TP
\fB\fImem_flags\fB\fR
affect whether allocation may block
.TP
\fB\fIdma\fB\fR
used to return DMA address of buffer
.SH "DESCRIPTION"
.PP
Return value is either null (indicating no buffer could be allocated), or
the cpu-space pointer to a buffer that may be used to perform DMA to the
specified device.  Such cpu-space buffers are returned along with the DMA
address (through the pointer provided).
.PP
These buffers are used with URB_NO_xxx_DMA_MAP set in urb->transfer_flags
to avoid behaviors like using ``DMA bounce buffers'', or tying down I/O
mapping hardware for long idle periods.  The implementation varies between
platforms, depending on details of how DMA will work to this device.
Using these buffers also helps prevent cacheline sharing problems on
architectures where CPU caches are not DMA-coherent.
.PP
When the buffer is no longer used, free it with \fBusb_buffer_free\fR.
.SH "ABOUT THIS DOCUMENT"
.PP
This documentation is free software; you can redistribute
it and/or modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later
version.
.PP
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
.PP
You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
MA 02111-1307 USA
.PP
For more details see the file COPYING in the source
distribution of Linux.
.PP
If you have comments on the formatting of this manpage, then please contact
Michael Still (mikal@stillhq.com).
.PP
This documentation was generated with kernel version 2.5.73.