[linux.git] / fs / udf / misc.c

/*
 * misc.c
 *
 * PURPOSE
 *	Miscellaneous routines for the OSTA-UDF(tm) filesystem.
 *
 * COPYRIGHT
 *	This file is distributed under the terms of the GNU General Public
 *	License (GPL). Copies of the GPL can be obtained from:
 *		ftp://prep.ai.mit.edu/pub/gnu/GPL
 *	Each contributing author retains all rights to their own work.
 *
 *  (C) 1998 Dave Boynton
 *  (C) 1998-2004 Ben Fennema
 *  (C) 1999-2000 Stelias Computing Inc
 *
 * HISTORY
 *
 *  04/19/99 blf  partial support for reading/writing specific EA's
 */

#include "udfdecl.h"

#include <linux/fs.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/crc-itu-t.h>

#include "udf_i.h"
#include "udf_sb.h"

struct buffer_head *udf_tgetblk(struct super_block *sb, int block)
{
	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
		return sb_getblk(sb, udf_fixed_to_variable(block));
	else
		return sb_getblk(sb, block);
}

struct buffer_head *udf_tread(struct super_block *sb, int block)
{
	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
		return sb_bread(sb, udf_fixed_to_variable(block));
	else
		return sb_bread(sb, block);
}

struct genericFormat *udf_add_extendedattr(struct inode *inode, uint32_t size,
					   uint32_t type, uint8_t loc)
{
	uint8_t *ea = NULL, *ad = NULL;
	int offset;
	uint16_t crclen;
	struct udf_inode_info *iinfo = UDF_I(inode);

	ea = iinfo->i_ext.i_data;
	if (iinfo->i_lenEAttr) {
		ad = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
	} else {
		ad = ea;
		size += sizeof(struct extendedAttrHeaderDesc);
	}

	offset = inode->i_sb->s_blocksize - udf_file_entry_alloc_offset(inode) -
		iinfo->i_lenAlloc;

	/* TODO - Check for FreeEASpace */

	if (loc & 0x01 && offset >= size) {
		struct extendedAttrHeaderDesc *eahd;
		eahd = (struct extendedAttrHeaderDesc *)ea;

		if (iinfo->i_lenAlloc)
			memmove(&ad[size], ad, iinfo->i_lenAlloc);

		if (iinfo->i_lenEAttr) {
			/* check checksum/crc */
			if (eahd->descTag.tagIdent !=
					cpu_to_le16(TAG_IDENT_EAHD) ||
			    le32_to_cpu(eahd->descTag.tagLocation) !=
					iinfo->i_location.logicalBlockNum)
				return NULL;
		} else {
			struct udf_sb_info *sbi = UDF_SB(inode->i_sb);

			size -= sizeof(struct extendedAttrHeaderDesc);
			iinfo->i_lenEAttr +=
				sizeof(struct extendedAttrHeaderDesc);
			eahd->descTag.tagIdent = cpu_to_le16(TAG_IDENT_EAHD);
			if (sbi->s_udfrev >= 0x0200)
				eahd->descTag.descVersion = cpu_to_le16(3);
			else
				eahd->descTag.descVersion = cpu_to_le16(2);
			eahd->descTag.tagSerialNum =
					cpu_to_le16(sbi->s_serial_number);
			eahd->descTag.tagLocation = cpu_to_le32(
					iinfo->i_location.logicalBlockNum);
			eahd->impAttrLocation = cpu_to_le32(0xFFFFFFFF);
			eahd->appAttrLocation = cpu_to_le32(0xFFFFFFFF);
		}

		offset = iinfo->i_lenEAttr;
		if (type < 2048) {
			if (le32_to_cpu(eahd->appAttrLocation) <
					iinfo->i_lenEAttr) {
				uint32_t aal =
					le32_to_cpu(eahd->appAttrLocation);
				memmove(&ea[offset - aal + size],
					&ea[aal], offset - aal);
				offset -= aal;
				eahd->appAttrLocation =
						cpu_to_le32(aal + size);
			}
			if (le32_to_cpu(eahd->impAttrLocation) <
					iinfo->i_lenEAttr) {
				uint32_t ial =
					le32_to_cpu(eahd->impAttrLocation);
				memmove(&ea[offset - ial + size],
					&ea[ial], offset - ial);
				offset -= ial;
				eahd->impAttrLocation =
						cpu_to_le32(ial + size);
			}
		} else if (type < 65536) {
			if (le32_to_cpu(eahd->appAttrLocation) <
					iinfo->i_lenEAttr) {
				uint32_t aal =
					le32_to_cpu(eahd->appAttrLocation);
				memmove(&ea[offset - aal + size],
					&ea[aal], offset - aal);
				offset -= aal;
				eahd->appAttrLocation =
						cpu_to_le32(aal + size);
			}
		}
		/* rewrite CRC + checksum of eahd */
		crclen = sizeof(struct extendedAttrHeaderDesc) - sizeof(struct tag);
		eahd->descTag.descCRCLength = cpu_to_le16(crclen);
		eahd->descTag.descCRC = cpu_to_le16(crc_itu_t(0, (char *)eahd +
						sizeof(struct tag), crclen));
		eahd->descTag.tagChecksum = udf_tag_checksum(&eahd->descTag);
		iinfo->i_lenEAttr += size;
		return (struct genericFormat *)&ea[offset];
	}
	if (loc & 0x02)
		;

	return NULL;
}

struct genericFormat *udf_get_extendedattr(struct inode *inode, uint32_t type,
					   uint8_t subtype)
{
	struct genericFormat *gaf;
	uint8_t *ea = NULL;
	uint32_t offset;
	struct udf_inode_info *iinfo = UDF_I(inode);

	ea = iinfo->i_ext.i_data;

	if (iinfo->i_lenEAttr) {
		struct extendedAttrHeaderDesc *eahd;
		eahd = (struct extendedAttrHeaderDesc *)ea;

		/* check checksum/crc */
		if (eahd->descTag.tagIdent !=
				cpu_to_le16(TAG_IDENT_EAHD) ||
		    le32_to_cpu(eahd->descTag.tagLocation) !=
				iinfo->i_location.logicalBlockNum)
			return NULL;

		if (type < 2048)
			offset = sizeof(struct extendedAttrHeaderDesc);
		else if (type < 65536)
			offset = le32_to_cpu(eahd->impAttrLocation);
		else
			offset = le32_to_cpu(eahd->appAttrLocation);

		while (offset < iinfo->i_lenEAttr) {
			gaf = (struct genericFormat *)&ea[offset];
			if (le32_to_cpu(gaf->attrType) == type &&
					gaf->attrSubtype == subtype)
				return gaf;
			else
				offset += le32_to_cpu(gaf->attrLength);
		}
	}

	return NULL;
}

/*
 * udf_read_tagged
 *
 * PURPOSE
 *	Read the first block of a tagged descriptor.
 *
 * HISTORY
 *	July 1, 1997 - Andrew E. Mileski
 *	Written, tested, and released.
 */
struct buffer_head *udf_read_tagged(struct super_block *sb, uint32_t block,
				    uint32_t location, uint16_t *ident)
{
	struct tag *tag_p;
	struct buffer_head *bh = NULL;
	u8 checksum;

	/* Read the block */
	if (block == 0xFFFFFFFF)
		return NULL;

	bh = udf_tread(sb, block);
	if (!bh) {
		udf_err(sb, "read failed, block=%u, location=%d\n",
			block, location);
		return NULL;
	}

	tag_p = (struct tag *)(bh->b_data);

	*ident = le16_to_cpu(tag_p->tagIdent);

	if (location != le32_to_cpu(tag_p->tagLocation)) {
		udf_debug("location mismatch block %u, tag %u != %u\n",
			  block, le32_to_cpu(tag_p->tagLocation), location);
		goto error_out;
	}

	/* Verify the tag checksum */
	checksum = udf_tag_checksum(tag_p);
	if (checksum != tag_p->tagChecksum) {
		udf_err(sb, "tag checksum failed, block %u: 0x%02x != 0x%02x\n",
			block, checksum, tag_p->tagChecksum);
		goto error_out;
	}

	/* Verify the tag version */
	if (tag_p->descVersion != cpu_to_le16(0x0002U) &&
	    tag_p->descVersion != cpu_to_le16(0x0003U)) {
		udf_err(sb, "tag version 0x%04x != 0x0002 || 0x0003, block %u\n",
			le16_to_cpu(tag_p->descVersion), block);
		goto error_out;
	}

	/* Verify the descriptor CRC */
	if (le16_to_cpu(tag_p->descCRCLength) + sizeof(struct tag) > sb->s_blocksize ||
	    le16_to_cpu(tag_p->descCRC) == crc_itu_t(0,
					bh->b_data + sizeof(struct tag),
					le16_to_cpu(tag_p->descCRCLength)))
		return bh;

	udf_debug("Crc failure block %d: crc = %d, crclen = %d\n", block,
		  le16_to_cpu(tag_p->descCRC),
		  le16_to_cpu(tag_p->descCRCLength));
error_out:
	brelse(bh);
	return NULL;
}

struct buffer_head *udf_read_ptagged(struct super_block *sb,
				     struct kernel_lb_addr *loc,
				     uint32_t offset, uint16_t *ident)
{
	return udf_read_tagged(sb, udf_get_lb_pblock(sb, loc, offset),
			       loc->logicalBlockNum + offset, ident);
}

void udf_update_tag(char *data, int length)
{
	struct tag *tptr = (struct tag *)data;
	length -= sizeof(struct tag);

	tptr->descCRCLength = cpu_to_le16(length);
	tptr->descCRC = cpu_to_le16(crc_itu_t(0, data + sizeof(struct tag), length));
	tptr->tagChecksum = udf_tag_checksum(tptr);
}

void udf_new_tag(char *data, uint16_t ident, uint16_t version, uint16_t snum,
		 uint32_t loc, int length)
{
	struct tag *tptr = (struct tag *)data;
	tptr->tagIdent = cpu_to_le16(ident);
	tptr->descVersion = cpu_to_le16(version);
	tptr->tagSerialNum = cpu_to_le16(snum);
	tptr->tagLocation = cpu_to_le32(loc);
	udf_update_tag(data, length);
}

u8 udf_tag_checksum(const struct tag *t)
{
	u8 *data = (u8 *)t;
	u8 checksum = 0;
	int i;
	for (i = 0; i < sizeof(struct tag); ++i)
		if (i != 4) /* position of checksum */
			checksum += data[i];
	return checksum;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* misc.c
	3	*
	4	* PURPOSE
	5	* Miscellaneous routines for the OSTA-UDF(tm) filesystem.
	6	*
1da177e4 LT	7	* COPYRIGHT
	8	* This file is distributed under the terms of the GNU General Public
	9	* License (GPL). Copies of the GPL can be obtained from:
	10	* ftp://prep.ai.mit.edu/pub/gnu/GPL
	11	* Each contributing author retains all rights to their own work.
	12	*
	13	* (C) 1998 Dave Boynton
	14	* (C) 1998-2004 Ben Fennema
	15	* (C) 1999-2000 Stelias Computing Inc
	16	*
	17	* HISTORY
	18	*
	19	* 04/19/99 blf partial support for reading/writing specific EA's
	20	*/
	21
	22	#include "udfdecl.h"
	23
	24	#include <linux/fs.h>
	25	#include <linux/string.h>
1da177e4	26	#include <linux/buffer_head.h>
f845fced	27	#include <linux/crc-itu-t.h>
1da177e4 LT	28
	29	#include "udf_i.h"
	30	#include "udf_sb.h"
	31
cb00ea35	32	struct buffer_head udf_tgetblk(struct super_block sb, int block)
1da177e4 LT	33	{
	34	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
	35	return sb_getblk(sb, udf_fixed_to_variable(block));
	36	else
	37	return sb_getblk(sb, block);
	38	}
	39
cb00ea35	40	struct buffer_head udf_tread(struct super_block sb, int block)
1da177e4 LT	41	{
	42	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
	43	return sb_bread(sb, udf_fixed_to_variable(block));
	44	else
	45	return sb_bread(sb, block);
	46	}
	47
cb00ea35 CG	48	struct genericFormat udf_add_extendedattr(struct inode inode, uint32_t size,
cb00ea35 CG	49	uint32_t type, uint8_t loc)
1da177e4 LT	50	{
	51	uint8_t ea = NULL, ad = NULL;
	52	int offset;
	53	uint16_t crclen;
48d6d8ff	54	struct udf_inode_info *iinfo = UDF_I(inode);
1da177e4	55
48d6d8ff MS	56	ea = iinfo->i_ext.i_data;
	57	if (iinfo->i_lenEAttr) {
	58	ad = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
28de7948	59	} else {
1da177e4 LT	60	ad = ea;
	61	size += sizeof(struct extendedAttrHeaderDesc);
	62	}
	63
	64	offset = inode->i_sb->s_blocksize - udf_file_entry_alloc_offset(inode) -
48d6d8ff	65	iinfo->i_lenAlloc;
1da177e4 LT	66
	67	/* TODO - Check for FreeEASpace */
	68
cb00ea35	69	if (loc & 0x01 && offset >= size) {
1da177e4 LT	70	struct extendedAttrHeaderDesc *eahd;
	71	eahd = (struct extendedAttrHeaderDesc *)ea;
	72
48d6d8ff MS	73	if (iinfo->i_lenAlloc)
48d6d8ff MS	74	memmove(&ad[size], ad, iinfo->i_lenAlloc);
1da177e4	75
48d6d8ff	76	if (iinfo->i_lenEAttr) {
1da177e4	77	/* check checksum/crc */
5e0f0017 MS	78	if (eahd->descTag.tagIdent !=
5e0f0017 MS	79	cpu_to_le16(TAG_IDENT_EAHD) \|\|
4b11111a	80	le32_to_cpu(eahd->descTag.tagLocation) !=
48d6d8ff	81	iinfo->i_location.logicalBlockNum)
1da177e4	82	return NULL;
cb00ea35	83	} else {
6c79e987 MS	84	struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
6c79e987 MS	85
1da177e4	86	size -= sizeof(struct extendedAttrHeaderDesc);
48d6d8ff	87	iinfo->i_lenEAttr +=
4b11111a	88	sizeof(struct extendedAttrHeaderDesc);
1da177e4	89	eahd->descTag.tagIdent = cpu_to_le16(TAG_IDENT_EAHD);
6c79e987	90	if (sbi->s_udfrev >= 0x0200)
1da177e4 LT	91	eahd->descTag.descVersion = cpu_to_le16(3);
	92	else
	93	eahd->descTag.descVersion = cpu_to_le16(2);
4b11111a MS	94	eahd->descTag.tagSerialNum =
	95	cpu_to_le16(sbi->s_serial_number);
	96	eahd->descTag.tagLocation = cpu_to_le32(
48d6d8ff	97	iinfo->i_location.logicalBlockNum);
1da177e4 LT	98	eahd->impAttrLocation = cpu_to_le32(0xFFFFFFFF);
	99	eahd->appAttrLocation = cpu_to_le32(0xFFFFFFFF);
	100	}
	101
48d6d8ff	102	offset = iinfo->i_lenEAttr;
cb00ea35	103	if (type < 2048) {
4b11111a	104	if (le32_to_cpu(eahd->appAttrLocation) <
48d6d8ff	105	iinfo->i_lenEAttr) {
4b11111a MS	106	uint32_t aal =
4b11111a MS	107	le32_to_cpu(eahd->appAttrLocation);
28de7948 CG	108	memmove(&ea[offset - aal + size],
28de7948 CG	109	&ea[aal], offset - aal);
1da177e4	110	offset -= aal;
4b11111a MS	111	eahd->appAttrLocation =
4b11111a MS	112	cpu_to_le32(aal + size);
1da177e4	113	}
4b11111a	114	if (le32_to_cpu(eahd->impAttrLocation) <
48d6d8ff	115	iinfo->i_lenEAttr) {
4b11111a MS	116	uint32_t ial =
4b11111a MS	117	le32_to_cpu(eahd->impAttrLocation);
28de7948 CG	118	memmove(&ea[offset - ial + size],
28de7948 CG	119	&ea[ial], offset - ial);
1da177e4	120	offset -= ial;
4b11111a MS	121	eahd->impAttrLocation =
4b11111a MS	122	cpu_to_le32(ial + size);
1da177e4	123	}
cb00ea35	124	} else if (type < 65536) {
4b11111a	125	if (le32_to_cpu(eahd->appAttrLocation) <
48d6d8ff	126	iinfo->i_lenEAttr) {
4b11111a MS	127	uint32_t aal =
4b11111a MS	128	le32_to_cpu(eahd->appAttrLocation);
28de7948 CG	129	memmove(&ea[offset - aal + size],
28de7948 CG	130	&ea[aal], offset - aal);
1da177e4	131	offset -= aal;
4b11111a MS	132	eahd->appAttrLocation =
4b11111a MS	133	cpu_to_le32(aal + size);
1da177e4 LT	134	}
	135	}
	136	/* rewrite CRC + checksum of eahd */
5ca4e4be	137	crclen = sizeof(struct extendedAttrHeaderDesc) - sizeof(struct tag);
1da177e4	138	eahd->descTag.descCRCLength = cpu_to_le16(crclen);
f845fced	139	eahd->descTag.descCRC = cpu_to_le16(crc_itu_t(0, (char *)eahd +
5ca4e4be	140	sizeof(struct tag), crclen));
3f2587bb	141	eahd->descTag.tagChecksum = udf_tag_checksum(&eahd->descTag);
48d6d8ff	142	iinfo->i_lenEAttr += size;
1da177e4 LT	143	return (struct genericFormat *)&ea[offset];
1da177e4 LT	144	}
4b11111a MS	145	if (loc & 0x02)
4b11111a MS	146	;
28de7948	147
1da177e4 LT	148	return NULL;
	149	}
	150
cb00ea35 CG	151	struct genericFormat udf_get_extendedattr(struct inode inode, uint32_t type,
cb00ea35 CG	152	uint8_t subtype)
1da177e4 LT	153	{
	154	struct genericFormat *gaf;
	155	uint8_t *ea = NULL;
	156	uint32_t offset;
48d6d8ff	157	struct udf_inode_info *iinfo = UDF_I(inode);
1da177e4	158
48d6d8ff	159	ea = iinfo->i_ext.i_data;
1da177e4	160
48d6d8ff	161	if (iinfo->i_lenEAttr) {
1da177e4 LT	162	struct extendedAttrHeaderDesc *eahd;
	163	eahd = (struct extendedAttrHeaderDesc *)ea;
	164
	165	/* check checksum/crc */
5e0f0017 MS	166	if (eahd->descTag.tagIdent !=
5e0f0017 MS	167	cpu_to_le16(TAG_IDENT_EAHD) \|\|
4b11111a	168	le32_to_cpu(eahd->descTag.tagLocation) !=
48d6d8ff	169	iinfo->i_location.logicalBlockNum)
1da177e4	170	return NULL;
cb00ea35	171
1da177e4 LT	172	if (type < 2048)
	173	offset = sizeof(struct extendedAttrHeaderDesc);
	174	else if (type < 65536)
	175	offset = le32_to_cpu(eahd->impAttrLocation);
	176	else
	177	offset = le32_to_cpu(eahd->appAttrLocation);
	178
48d6d8ff	179	while (offset < iinfo->i_lenEAttr) {
1da177e4	180	gaf = (struct genericFormat *)&ea[offset];
4b11111a MS	181	if (le32_to_cpu(gaf->attrType) == type &&
4b11111a MS	182	gaf->attrSubtype == subtype)
1da177e4 LT	183	return gaf;
	184	else
	185	offset += le32_to_cpu(gaf->attrLength);
	186	}
	187	}
28de7948	188
1da177e4 LT	189	return NULL;
	190	}
	191
	192	/*
	193	* udf_read_tagged
	194	*
	195	* PURPOSE
	196	* Read the first block of a tagged descriptor.
	197	*
	198	* HISTORY
	199	* July 1, 1997 - Andrew E. Mileski
	200	* Written, tested, and released.
	201	*/
cb00ea35	202	struct buffer_head udf_read_tagged(struct super_block sb, uint32_t block,
4b11111a	203	uint32_t location, uint16_t *ident)
1da177e4	204	{
5ca4e4be	205	struct tag *tag_p;
1da177e4	206	struct buffer_head *bh = NULL;
7e273e3b	207	u8 checksum;
1da177e4 LT	208
	209	/* Read the block */
	210	if (block == 0xFFFFFFFF)
	211	return NULL;
	212
f4bcbbd9	213	bh = udf_tread(sb, block);
cb00ea35	214	if (!bh) {
8076c363 JP	215	udf_err(sb, "read failed, block=%u, location=%d\n",
8076c363 JP	216	block, location);
1da177e4 LT	217	return NULL;
	218	}
	219
5ca4e4be	220	tag_p = (struct tag *)(bh->b_data);
1da177e4 LT	221
	222	*ident = le16_to_cpu(tag_p->tagIdent);
	223
cb00ea35	224	if (location != le32_to_cpu(tag_p->tagLocation)) {
1da177e4	225	udf_debug("location mismatch block %u, tag %u != %u\n",
f4bcbbd9	226	block, le32_to_cpu(tag_p->tagLocation), location);
1da177e4 LT	227	goto error_out;
1da177e4 LT	228	}
cb00ea35	229
1da177e4	230	/* Verify the tag checksum */
7e273e3b JP	231	checksum = udf_tag_checksum(tag_p);
7e273e3b JP	232	if (checksum != tag_p->tagChecksum) {
8076c363 JP	233	udf_err(sb, "tag checksum failed, block %u: 0x%02x != 0x%02x\n",
8076c363 JP	234	block, checksum, tag_p->tagChecksum);
1da177e4 LT	235	goto error_out;
	236	}
	237
	238	/* Verify the tag version */
5e0f0017 MS	239	if (tag_p->descVersion != cpu_to_le16(0x0002U) &&
5e0f0017 MS	240	tag_p->descVersion != cpu_to_le16(0x0003U)) {
8076c363 JP	241	udf_err(sb, "tag version 0x%04x != 0x0002 \|\| 0x0003, block %u\n",
8076c363 JP	242	le16_to_cpu(tag_p->descVersion), block);
1da177e4 LT	243	goto error_out;
	244	}
	245
	246	/* Verify the descriptor CRC */
5ca4e4be	247	if (le16_to_cpu(tag_p->descCRCLength) + sizeof(struct tag) > sb->s_blocksize \|\|
f845fced	248	le16_to_cpu(tag_p->descCRC) == crc_itu_t(0,
5ca4e4be	249	bh->b_data + sizeof(struct tag),
f845fced	250	le16_to_cpu(tag_p->descCRCLength)))
1da177e4	251	return bh;
4b11111a	252
f4bcbbd9	253	udf_debug("Crc failure block %d: crc = %d, crclen = %d\n", block,
8076c363 JP	254	le16_to_cpu(tag_p->descCRC),
8076c363 JP	255	le16_to_cpu(tag_p->descCRCLength));
28de7948	256	error_out:
1da177e4 LT	257	brelse(bh);
	258	return NULL;
	259	}
	260
97e961fd PE	261	struct buffer_head udf_read_ptagged(struct super_block sb,
97e961fd PE	262	struct kernel_lb_addr *loc,
4b11111a	263	uint32_t offset, uint16_t *ident)
1da177e4 LT	264	{
1da177e4 LT	265	return udf_read_tagged(sb, udf_get_lb_pblock(sb, loc, offset),
97e961fd	266	loc->logicalBlockNum + offset, ident);
1da177e4 LT	267	}
1da177e4 LT	268
1da177e4 LT	269	void udf_update_tag(char *data, int length)
1da177e4 LT	270	{
5ca4e4be PE	271	struct tag tptr = (struct tag )data;
5ca4e4be PE	272	length -= sizeof(struct tag);
1da177e4	273
1da177e4	274	tptr->descCRCLength = cpu_to_le16(length);
5ca4e4be	275	tptr->descCRC = cpu_to_le16(crc_itu_t(0, data + sizeof(struct tag), length));
3f2587bb	276	tptr->tagChecksum = udf_tag_checksum(tptr);
1da177e4 LT	277	}
	278
	279	void udf_new_tag(char *data, uint16_t ident, uint16_t version, uint16_t snum,
cb00ea35	280	uint32_t loc, int length)
1da177e4	281	{
5ca4e4be	282	struct tag tptr = (struct tag )data;
1da177e4 LT	283	tptr->tagIdent = cpu_to_le16(ident);
	284	tptr->descVersion = cpu_to_le16(version);
	285	tptr->tagSerialNum = cpu_to_le16(snum);
	286	tptr->tagLocation = cpu_to_le32(loc);
	287	udf_update_tag(data, length);
	288	}
3f2587bb	289
5ca4e4be	290	u8 udf_tag_checksum(const struct tag *t)
3f2587bb MS	291	{
	292	u8 data = (u8 )t;
	293	u8 checksum = 0;
	294	int i;
5ca4e4be	295	for (i = 0; i < sizeof(struct tag); ++i)
3f2587bb MS	296	if (i != 4) /* position of checksum */
	297	checksum += data[i];
	298	return checksum;
	299	}