1 /* 2 * Copyright (C) 2007 Michael Brown <mbrown (at) fensystems.co.uk>. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License as 6 * published by the Free Software Foundation; either version 2 of the 7 * License, or any later version. 8 * 9 * This program is distributed in the hope that it will be useful, but 10 * WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, write to the Free Software 16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 17 */ 18 19 FILE_LICENCE ( GPL2_OR_LATER ); 20 21 /** 22 * @file 23 * 24 * I/O buffer padding 25 * 26 */ 27 28 #include <string.h> 29 #include <gpxe/iobuf.h> 30 31 /** 32 * Pad I/O buffer 33 * 34 * @v iobuf I/O buffer 35 * @v min_len Minimum length 36 * 37 * This function pads and aligns I/O buffers, for devices that 38 * aren't capable of padding in hardware, or that require specific 39 * alignment in TX buffers. The packet data will end up aligned to a 40 * multiple of @c IOB_ALIGN. 41 * 42 * @c min_len must not exceed @v IOB_ZLEN. 43 */ 44 void iob_pad ( struct io_buffer *iobuf, size_t min_len ) { 45 void *data; 46 size_t len; 47 size_t headroom; 48 signed int pad_len; 49 50 assert ( min_len <= IOB_ZLEN ); 51 52 /* Move packet data to start of I/O buffer. This will both 53 * align the data (since I/O buffers are aligned to 54 * IOB_ALIGN) and give us sufficient space for the 55 * zero-padding 56 */ 57 data = iobuf->data; 58 len = iob_len ( iobuf ); 59 headroom = iob_headroom ( iobuf ); 60 iob_push ( iobuf, headroom ); 61 memmove ( iobuf->data, data, len ); 62 iob_unput ( iobuf, headroom ); 63 64 /* Pad to minimum packet length */ 65 pad_len = ( min_len - iob_len ( iobuf ) ); 66 if ( pad_len > 0 ) 67 memset ( iob_put ( iobuf, pad_len ), 0, pad_len ); 68 } 69
