2 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
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.
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.
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., 51 Franklin Street, Fifth Floor, Boston, MA
20 FILE_LICENCE ( GPL2_OR_LATER );
30 #include <ipxe/iobuf.h>
36 * @v min_len Minimum length
38 * This function pads and aligns I/O buffers, for devices that
39 * aren't capable of padding in hardware, or that require specific
40 * alignment in TX buffers. The packet data will end up aligned to a
41 * multiple of @c IOB_ALIGN.
43 * @c min_len must not exceed @v IOB_ZLEN.
45 void iob_pad ( struct io_buffer *iobuf, size_t min_len ) {
51 assert ( min_len <= IOB_ZLEN );
53 /* Move packet data to start of I/O buffer. This will both
54 * align the data (since I/O buffers are aligned to
55 * IOB_ALIGN) and give us sufficient space for the
59 len = iob_len ( iobuf );
60 headroom = iob_headroom ( iobuf );
61 iob_push ( iobuf, headroom );
62 memmove ( iobuf->data, data, len );
63 iob_unput ( iobuf, headroom );
65 /* Pad to minimum packet length */
66 pad_len = ( min_len - iob_len ( iobuf ) );
68 memset ( iob_put ( iobuf, pad_len ), 0, pad_len );