On Thursday 17 May 2007, Hans Petter Selasky wrote: > Isn't that the job of "usb_buffer_alloc()", to allocate memory in blocks of > PAGE_SIZE bytes?
Not at all. The "size" parameter is in bytes, and the utility code it calls goes to some lengths to *avoid* that kind of wastage. As they say: UTSL! The original reason to have such routines was to allocate small buffers for HID devices on systems where DMA map/unmap operations were absurdly expensive on such small buffers. (Think IOMMU ops across a slowish bus.) > Is it right understood that the Linux USB stack does currently not use > scatter > and gathering? To me it seems like that, hence in the URB Linux only has a > single DMA address value. Let me guess -- you didn't read my response on that topic ... ? ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
