[GitHub/moto-9609/android_kernel_motorola_exynos9610.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 "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(tag);
		eahd->descTag.descCRCLength = cpu_to_le16(crclen);
		eahd->descTag.descCRC = cpu_to_le16(udf_crc((char *)eahd +
						sizeof(tag), crclen, 0));
		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)
{
	tag *tag_p;
	struct buffer_head *bh = NULL;
	struct udf_sb_info *sbi = UDF_SB(sb);

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

	bh = udf_tread(sb, block + sbi->s_session);
	if (!bh) {
		udf_debug("block=%d, location=%d: read failed\n",
			  block + sbi->s_session, location);
		return NULL;
	}

	tag_p = (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 + sbi->s_session,
			  le32_to_cpu(tag_p->tagLocation), location);
		goto error_out;
	}

	/* Verify the tag checksum */
	if (udf_tag_checksum(tag_p) != tag_p->tagChecksum) {
		printk(KERN_ERR "udf: tag checksum failed block %d\n", block);
		goto error_out;
	}

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

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

	udf_debug("Crc failure block %d: crc = %d, crclen = %d\n",
		  block + sbi->s_session, 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, 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)
{
	tag *tptr = (tag *)data;
	length -= sizeof(tag);

	tptr->descCRCLength = cpu_to_le16(length);
	tptr->descCRC = cpu_to_le16(udf_crc(data + sizeof(tag), length, 0));
	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)
{
	tag *tptr = (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 tag *t)
{
	u8 *data = (u8 *)t;
	u8 checksum = 0;
	int i;
	for (i = 0; i < sizeof(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 LT	26	#include <linux/buffer_head.h>
	27
	28	#include "udf_i.h"
	29	#include "udf_sb.h"
	30
cb00ea35	31	struct buffer_head udf_tgetblk(struct super_block sb, int block)
1da177e4 LT	32	{
	33	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
	34	return sb_getblk(sb, udf_fixed_to_variable(block));
	35	else
	36	return sb_getblk(sb, block);
	37	}
	38
cb00ea35	39	struct buffer_head udf_tread(struct super_block sb, int block)
1da177e4 LT	40	{
	41	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
	42	return sb_bread(sb, udf_fixed_to_variable(block));
	43	else
	44	return sb_bread(sb, block);
	45	}
	46
cb00ea35 CG	47	struct genericFormat udf_add_extendedattr(struct inode inode, uint32_t size,
cb00ea35 CG	48	uint32_t type, uint8_t loc)
1da177e4 LT	49	{
	50	uint8_t ea = NULL, ad = NULL;
	51	int offset;
	52	uint16_t crclen;
48d6d8ff	53	struct udf_inode_info *iinfo = UDF_I(inode);
1da177e4	54
48d6d8ff MS	55	ea = iinfo->i_ext.i_data;
	56	if (iinfo->i_lenEAttr) {
	57	ad = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
28de7948	58	} else {
1da177e4 LT	59	ad = ea;
	60	size += sizeof(struct extendedAttrHeaderDesc);
	61	}
	62
	63	offset = inode->i_sb->s_blocksize - udf_file_entry_alloc_offset(inode) -
48d6d8ff	64	iinfo->i_lenAlloc;
1da177e4 LT	65
	66	/* TODO - Check for FreeEASpace */
	67
cb00ea35	68	if (loc & 0x01 && offset >= size) {
1da177e4 LT	69	struct extendedAttrHeaderDesc *eahd;
	70	eahd = (struct extendedAttrHeaderDesc *)ea;
	71
48d6d8ff MS	72	if (iinfo->i_lenAlloc)
48d6d8ff MS	73	memmove(&ad[size], ad, iinfo->i_lenAlloc);
1da177e4	74
48d6d8ff	75	if (iinfo->i_lenEAttr) {
1da177e4	76	/* check checksum/crc */
5e0f0017 MS	77	if (eahd->descTag.tagIdent !=
5e0f0017 MS	78	cpu_to_le16(TAG_IDENT_EAHD) \|\|
4b11111a	79	le32_to_cpu(eahd->descTag.tagLocation) !=
48d6d8ff	80	iinfo->i_location.logicalBlockNum)
1da177e4	81	return NULL;
cb00ea35	82	} else {
6c79e987 MS	83	struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
6c79e987 MS	84
1da177e4	85	size -= sizeof(struct extendedAttrHeaderDesc);
48d6d8ff	86	iinfo->i_lenEAttr +=
4b11111a	87	sizeof(struct extendedAttrHeaderDesc);
1da177e4	88	eahd->descTag.tagIdent = cpu_to_le16(TAG_IDENT_EAHD);
6c79e987	89	if (sbi->s_udfrev >= 0x0200)
1da177e4 LT	90	eahd->descTag.descVersion = cpu_to_le16(3);
	91	else
	92	eahd->descTag.descVersion = cpu_to_le16(2);
4b11111a MS	93	eahd->descTag.tagSerialNum =
	94	cpu_to_le16(sbi->s_serial_number);
	95	eahd->descTag.tagLocation = cpu_to_le32(
48d6d8ff	96	iinfo->i_location.logicalBlockNum);
1da177e4 LT	97	eahd->impAttrLocation = cpu_to_le32(0xFFFFFFFF);
	98	eahd->appAttrLocation = cpu_to_le32(0xFFFFFFFF);
	99	}
	100
48d6d8ff	101	offset = iinfo->i_lenEAttr;
cb00ea35	102	if (type < 2048) {
4b11111a	103	if (le32_to_cpu(eahd->appAttrLocation) <
48d6d8ff	104	iinfo->i_lenEAttr) {
4b11111a MS	105	uint32_t aal =
4b11111a MS	106	le32_to_cpu(eahd->appAttrLocation);
28de7948 CG	107	memmove(&ea[offset - aal + size],
28de7948 CG	108	&ea[aal], offset - aal);
1da177e4	109	offset -= aal;
4b11111a MS	110	eahd->appAttrLocation =
4b11111a MS	111	cpu_to_le32(aal + size);
1da177e4	112	}
4b11111a	113	if (le32_to_cpu(eahd->impAttrLocation) <
48d6d8ff	114	iinfo->i_lenEAttr) {
4b11111a MS	115	uint32_t ial =
4b11111a MS	116	le32_to_cpu(eahd->impAttrLocation);
28de7948 CG	117	memmove(&ea[offset - ial + size],
28de7948 CG	118	&ea[ial], offset - ial);
1da177e4	119	offset -= ial;
4b11111a MS	120	eahd->impAttrLocation =
4b11111a MS	121	cpu_to_le32(ial + size);
1da177e4	122	}
cb00ea35	123	} else if (type < 65536) {
4b11111a	124	if (le32_to_cpu(eahd->appAttrLocation) <
48d6d8ff	125	iinfo->i_lenEAttr) {
4b11111a MS	126	uint32_t aal =
4b11111a MS	127	le32_to_cpu(eahd->appAttrLocation);
28de7948 CG	128	memmove(&ea[offset - aal + size],
28de7948 CG	129	&ea[aal], offset - aal);
1da177e4	130	offset -= aal;
4b11111a MS	131	eahd->appAttrLocation =
4b11111a MS	132	cpu_to_le32(aal + size);
1da177e4 LT	133	}
	134	}
	135	/* rewrite CRC + checksum of eahd */
	136	crclen = sizeof(struct extendedAttrHeaderDesc) - sizeof(tag);
	137	eahd->descTag.descCRCLength = cpu_to_le16(crclen);
28de7948	138	eahd->descTag.descCRC = cpu_to_le16(udf_crc((char *)eahd +
4b11111a	139	sizeof(tag), crclen, 0));
3f2587bb	140	eahd->descTag.tagChecksum = udf_tag_checksum(&eahd->descTag);
48d6d8ff	141	iinfo->i_lenEAttr += size;
1da177e4 LT	142	return (struct genericFormat *)&ea[offset];
1da177e4 LT	143	}
4b11111a MS	144	if (loc & 0x02)
4b11111a MS	145	;
28de7948	146
1da177e4 LT	147	return NULL;
	148	}
	149
cb00ea35 CG	150	struct genericFormat udf_get_extendedattr(struct inode inode, uint32_t type,
cb00ea35 CG	151	uint8_t subtype)
1da177e4 LT	152	{
	153	struct genericFormat *gaf;
	154	uint8_t *ea = NULL;
	155	uint32_t offset;
48d6d8ff	156	struct udf_inode_info *iinfo = UDF_I(inode);
1da177e4	157
48d6d8ff	158	ea = iinfo->i_ext.i_data;
1da177e4	159
48d6d8ff	160	if (iinfo->i_lenEAttr) {
1da177e4 LT	161	struct extendedAttrHeaderDesc *eahd;
	162	eahd = (struct extendedAttrHeaderDesc *)ea;
	163
	164	/* check checksum/crc */
5e0f0017 MS	165	if (eahd->descTag.tagIdent !=
5e0f0017 MS	166	cpu_to_le16(TAG_IDENT_EAHD) \|\|
4b11111a	167	le32_to_cpu(eahd->descTag.tagLocation) !=
48d6d8ff	168	iinfo->i_location.logicalBlockNum)
1da177e4	169	return NULL;
cb00ea35	170
1da177e4 LT	171	if (type < 2048)
	172	offset = sizeof(struct extendedAttrHeaderDesc);
	173	else if (type < 65536)
	174	offset = le32_to_cpu(eahd->impAttrLocation);
	175	else
	176	offset = le32_to_cpu(eahd->appAttrLocation);
	177
48d6d8ff	178	while (offset < iinfo->i_lenEAttr) {
1da177e4	179	gaf = (struct genericFormat *)&ea[offset];
4b11111a MS	180	if (le32_to_cpu(gaf->attrType) == type &&
4b11111a MS	181	gaf->attrSubtype == subtype)
1da177e4 LT	182	return gaf;
	183	else
	184	offset += le32_to_cpu(gaf->attrLength);
	185	}
	186	}
28de7948	187
1da177e4 LT	188	return NULL;
	189	}
	190
	191	/*
	192	* udf_read_tagged
	193	*
	194	* PURPOSE
	195	* Read the first block of a tagged descriptor.
	196	*
	197	* HISTORY
	198	* July 1, 1997 - Andrew E. Mileski
	199	* Written, tested, and released.
	200	*/
cb00ea35	201	struct buffer_head udf_read_tagged(struct super_block sb, uint32_t block,
4b11111a	202	uint32_t location, uint16_t *ident)
1da177e4 LT	203	{
	204	tag *tag_p;
	205	struct buffer_head *bh = NULL;
6c79e987	206	struct udf_sb_info *sbi = UDF_SB(sb);
1da177e4 LT	207
	208	/* Read the block */
	209	if (block == 0xFFFFFFFF)
	210	return NULL;
	211
6c79e987	212	bh = udf_tread(sb, block + sbi->s_session);
cb00ea35 CG	213	if (!bh) {
cb00ea35 CG	214	udf_debug("block=%d, location=%d: read failed\n",
6c79e987	215	block + sbi->s_session, location);
1da177e4 LT	216	return NULL;
	217	}
	218
28de7948	219	tag_p = (tag *)(bh->b_data);
1da177e4 LT	220
	221	*ident = le16_to_cpu(tag_p->tagIdent);
	222
cb00ea35	223	if (location != le32_to_cpu(tag_p->tagLocation)) {
1da177e4	224	udf_debug("location mismatch block %u, tag %u != %u\n",
4b11111a MS	225	block + sbi->s_session,
4b11111a MS	226	le32_to_cpu(tag_p->tagLocation), location);
1da177e4 LT	227	goto error_out;
1da177e4 LT	228	}
cb00ea35	229
1da177e4	230	/* Verify the tag checksum */
3f2587bb	231	if (udf_tag_checksum(tag_p) != tag_p->tagChecksum) {
1da177e4 LT	232	printk(KERN_ERR "udf: tag checksum failed block %d\n", block);
	233	goto error_out;
	234	}
	235
	236	/* Verify the tag version */
5e0f0017 MS	237	if (tag_p->descVersion != cpu_to_le16(0x0002U) &&
5e0f0017 MS	238	tag_p->descVersion != cpu_to_le16(0x0003U)) {
1da177e4	239	udf_debug("tag version 0x%04x != 0x0002 \|\| 0x0003 block %d\n",
cb00ea35	240	le16_to_cpu(tag_p->descVersion), block);
1da177e4 LT	241	goto error_out;
	242	}
	243
	244	/* Verify the descriptor CRC */
	245	if (le16_to_cpu(tag_p->descCRCLength) + sizeof(tag) > sb->s_blocksize \|\|
cb00ea35	246	le16_to_cpu(tag_p->descCRC) == udf_crc(bh->b_data + sizeof(tag),
4b11111a	247	le16_to_cpu(tag_p->descCRCLength), 0))
1da177e4	248	return bh;
4b11111a	249
1da177e4	250	udf_debug("Crc failure block %d: crc = %d, crclen = %d\n",
6c79e987	251	block + sbi->s_session, le16_to_cpu(tag_p->descCRC),
cb00ea35	252	le16_to_cpu(tag_p->descCRCLength));
1da177e4	253
28de7948	254	error_out:
1da177e4 LT	255	brelse(bh);
	256	return NULL;
	257	}
	258
cb00ea35	259	struct buffer_head udf_read_ptagged(struct super_block sb, kernel_lb_addr loc,
4b11111a	260	uint32_t offset, uint16_t *ident)
1da177e4 LT	261	{
1da177e4 LT	262	return udf_read_tagged(sb, udf_get_lb_pblock(sb, loc, offset),
cb00ea35	263	loc.logicalBlockNum + offset, ident);
1da177e4 LT	264	}
1da177e4 LT	265
1da177e4 LT	266	void udf_update_tag(char *data, int length)
1da177e4 LT	267	{
28de7948	268	tag tptr = (tag )data;
1da177e4 LT	269	length -= sizeof(tag);
1da177e4 LT	270
1da177e4 LT	271	tptr->descCRCLength = cpu_to_le16(length);
1da177e4 LT	272	tptr->descCRC = cpu_to_le16(udf_crc(data + sizeof(tag), length, 0));
3f2587bb	273	tptr->tagChecksum = udf_tag_checksum(tptr);
1da177e4 LT	274	}
	275
	276	void udf_new_tag(char *data, uint16_t ident, uint16_t version, uint16_t snum,
cb00ea35	277	uint32_t loc, int length)
1da177e4	278	{
28de7948	279	tag tptr = (tag )data;
1da177e4 LT	280	tptr->tagIdent = cpu_to_le16(ident);
	281	tptr->descVersion = cpu_to_le16(version);
	282	tptr->tagSerialNum = cpu_to_le16(snum);
	283	tptr->tagLocation = cpu_to_le32(loc);
	284	udf_update_tag(data, length);
	285	}
3f2587bb MS	286
	287	u8 udf_tag_checksum(const tag *t)
	288	{
	289	u8 data = (u8 )t;
	290	u8 checksum = 0;
	291	int i;
	292	for (i = 0; i < sizeof(tag); ++i)
	293	if (i != 4) /* position of checksum */
	294	checksum += data[i];
	295	return checksum;
	296	}