void * usb_buffer_alloc (struct usb_device * dev, size_t size, int mem_flags, dma_addr_t * dma);
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).
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.
When the buffer is no longer used, free it with usb_buffer_free.
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.
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.
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
For more details see the file COPYING in the source distribution of Linux.
If you have comments on the formatting of this manpage, then please contact Michael Still (mikal@stillhq.com).
This documentation was generated with kernel version 2.6.0.