File:  [DragonFly] / src / sys / sys / disklabel.h
Revision 1.6: download - view: text, annotated - select for diffs
Wed May 19 22:53:02 2004 UTC (10 years, 7 months ago) by dillon
Branches: MAIN
CVS tags: HEAD
Device layer rollup commit.

* cdevsw_add() is now required.  cdevsw_add() and cdevsw_remove() may specify
  a mask/match indicating the range of supported minor numbers.  Multiple
  cdevsw_add()'s using the same major number, but distinctly different
  ranges, may be issued.  All devices that failed to call cdevsw_add() before
  now do.

* cdevsw_remove() now automatically marks all devices within its supported
  range as being destroyed.

* vnode->v_rdev is no longer resolved when the vnode is created.  Instead,
  only v_udev (a newly added field) is resolved.  v_rdev is resolved when
  the vnode is opened and cleared on the last close.

* A great deal of code was making rather dubious assumptions with regards
  to the validity of devices associated with vnodes, primarily due to
  the persistence of a device structure due to being indexed by (major, minor)
  instead of by (cdevsw, major, minor).  In particular, if you run a program
  which connects to a USB device and then you pull the USB device and plug
  it back in, the vnode subsystem will continue to believe that the device
  is open when, in fact, it isn't (because it was destroyed and recreated).

  In particular, note that all the VFS mount procedures now check devices
  via v_udev instead of v_rdev prior to calling VOP_OPEN(), since v_rdev
  is NULL prior to the first open.

* The disk layer's device interaction has been rewritten.  The disk layer
  (i.e. the slice and disklabel management layer) no longer overloads
  its data onto the device structure representing the underlying physical
  disk.  Instead, the disk layer uses the new cdevsw_add() functionality
  to register its own cdevsw using the underlying device's major number,
  and simply does NOT register the underlying device's cdevsw.  No
  confusion is created because the device hash is now based on
  (cdevsw,major,minor) rather then (major,minor).

  NOTE: This also means that underlying raw disk devices may use the entire
  device minor number instead of having to reserve the bits used by the disk
  layer, and also means that can we (theoretically) stack a fully
  disklabel-supported 'disk' on top of any block device.

* The new reference counting scheme prevents this by associating a device
  with a cdevsw and disconnecting the device from its cdevsw when the cdevsw
  is removed.  Additionally, all udev2dev() lookups run through the cdevsw
  mask/match and only successfully find devices still associated with an
  active cdevsw.

* Major work on MFS:  MFS no longer shortcuts vnode and device creation.  It
  now creates a real vnode and a real device and implements real open and
  close VOPs.  Additionally, due to the disk layer changes, MFS is no longer
  limited to 255 mounts.  The new limit is 16 million.  Since MFS creates a
  real device node, mount_mfs will now create a real /dev/mfs<PID> device
  that can be read from userland (e.g. so you can dump an MFS filesystem).

* BUF AND DEVICE STRATEGY changes.  The struct buf contains a b_dev field.
  In order to properly handle stacked devices we now require that the b_dev
  field be initialized before the device strategy routine is called.  This
  required some additional work in various VFS implementations.  To enforce
  this requirement, biodone() now sets b_dev to NODEV.  The new disk layer
  will adjust b_dev before forwarding a request to the actual physical
  device.

* A bug in the ISO CD boot sequence which resulted in a panic has been fixed.

Testing by: lots of people, but David Rhodus found the most aggregious bugs.

    1: /*
    2:  * Copyright (c) 1987, 1988, 1993
    3:  *	The Regents of the University of California.  All rights reserved.
    4:  *
    5:  * Redistribution and use in source and binary forms, with or without
    6:  * modification, are permitted provided that the following conditions
    7:  * are met:
    8:  * 1. Redistributions of source code must retain the above copyright
    9:  *    notice, this list of conditions and the following disclaimer.
   10:  * 2. Redistributions in binary form must reproduce the above copyright
   11:  *    notice, this list of conditions and the following disclaimer in the
   12:  *    documentation and/or other materials provided with the distribution.
   13:  * 3. All advertising materials mentioning features or use of this software
   14:  *    must display the following acknowledgement:
   15:  *	This product includes software developed by the University of
   16:  *	California, Berkeley and its contributors.
   17:  * 4. Neither the name of the University nor the names of its contributors
   18:  *    may be used to endorse or promote products derived from this software
   19:  *    without specific prior written permission.
   20:  *
   21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31:  * SUCH DAMAGE.
   32:  *
   33:  *	@(#)disklabel.h	8.2 (Berkeley) 7/10/94
   34:  * $FreeBSD: src/sys/sys/disklabel.h,v 1.49.2.7 2001/05/27 05:58:26 jkh Exp $
   35:  * $DragonFly: src/sys/sys/disklabel.h,v 1.6 2004/05/19 22:53:02 dillon Exp $
   36:  */
   37: 
   38: #ifndef _SYS_DISKLABEL_H_
   39: #define	_SYS_DISKLABEL_H_
   40: 
   41: #ifndef _KERNEL
   42: #include <sys/types.h>
   43: #endif
   44: #include <sys/ioccom.h>
   45: #include <sys/conf.h>
   46: 
   47: /*
   48:  * Disk description table, see disktab(5)
   49:  */
   50: #define	_PATH_DISKTAB	"/etc/disktab"
   51: #define	DISKTAB		"/etc/disktab"		/* deprecated */
   52: 
   53: /*
   54:  * Each disk has a label which includes information about the hardware
   55:  * disk geometry, filesystem partitions, and drive specific information.
   56:  * The label is in block 0 or 1, possibly offset from the beginning
   57:  * to leave room for a bootstrap, etc.
   58:  */
   59: 
   60: /* XXX these should be defined per controller (or drive) elsewhere, not here! */
   61: #ifdef __i386__
   62: #define LABELSECTOR	1			/* sector containing label */
   63: #define LABELOFFSET	0			/* offset of label in sector */
   64: #endif
   65: 
   66: #ifdef __alpha__
   67: #define LABELSECTOR	0
   68: #define LABELOFFSET	64
   69: #endif
   70: 
   71: #ifndef	LABELSECTOR
   72: #define LABELSECTOR	0			/* sector containing label */
   73: #endif
   74: 
   75: #ifndef	LABELOFFSET
   76: #define LABELOFFSET	64			/* offset of label in sector */
   77: #endif
   78: 
   79: #define DISKMAGIC	((u_int32_t)0x82564557)	/* The disk magic number */
   80: #ifndef MAXPARTITIONS
   81: #define	MAXPARTITIONS	16
   82: #endif
   83: 
   84: #define	LABEL_PART	2		/* partition containing label */
   85: #define	RAW_PART	2		/* partition containing whole disk */
   86: #define	SWAP_PART	1		/* partition normally containing swap */
   87: 
   88: #ifndef LOCORE
   89: struct disklabel {
   90: 	u_int32_t d_magic;		/* the magic number */
   91: 	u_int16_t d_type;		/* drive type */
   92: 	u_int16_t d_subtype;		/* controller/d_type specific */
   93: 	char	  d_typename[16];	/* type name, e.g. "eagle" */
   94: 
   95: 	/* 
   96: 	 * d_packname contains the pack identifier and is returned when
   97: 	 * the disklabel is read off the disk or in-core copy.
   98: 	 * d_boot0 and d_boot1 are the (optional) names of the
   99: 	 * primary (block 0) and secondary (block 1-15) bootstraps
  100: 	 * as found in /boot.  These are returned when using
  101: 	 * getdiskbyname(3) to retrieve the values from /etc/disktab.
  102: 	 */
  103: 	union {
  104: 		char	un_d_packname[16];	/* pack identifier */
  105: 		struct {
  106: 			char *un_d_boot0;	/* primary bootstrap name */
  107: 			char *un_d_boot1;	/* secondary bootstrap name */
  108: 		} un_b;
  109: 	} d_un;
  110: #define d_packname	d_un.un_d_packname
  111: #define d_boot0		d_un.un_b.un_d_boot0
  112: #define d_boot1		d_un.un_b.un_d_boot1
  113: 
  114: 			/* disk geometry: */
  115: 	u_int32_t d_secsize;		/* # of bytes per sector */
  116: 	u_int32_t d_nsectors;		/* # of data sectors per track */
  117: 	u_int32_t d_ntracks;		/* # of tracks per cylinder */
  118: 	u_int32_t d_ncylinders;		/* # of data cylinders per unit */
  119: 	u_int32_t d_secpercyl;		/* # of data sectors per cylinder */
  120: 	u_int32_t d_secperunit;		/* # of data sectors per unit */
  121: 
  122: 	/*
  123: 	 * Spares (bad sector replacements) below are not counted in
  124: 	 * d_nsectors or d_secpercyl.  Spare sectors are assumed to
  125: 	 * be physical sectors which occupy space at the end of each
  126: 	 * track and/or cylinder.
  127: 	 */
  128: 	u_int16_t d_sparespertrack;	/* # of spare sectors per track */
  129: 	u_int16_t d_sparespercyl;	/* # of spare sectors per cylinder */
  130: 	/*
  131: 	 * Alternate cylinders include maintenance, replacement, configuration
  132: 	 * description areas, etc.
  133: 	 */
  134: 	u_int32_t d_acylinders;		/* # of alt. cylinders per unit */
  135: 
  136: 			/* hardware characteristics: */
  137: 	/*
  138: 	 * d_interleave, d_trackskew and d_cylskew describe perturbations
  139: 	 * in the media format used to compensate for a slow controller.
  140: 	 * Interleave is physical sector interleave, set up by the
  141: 	 * formatter or controller when formatting.  When interleaving is
  142: 	 * in use, logically adjacent sectors are not physically
  143: 	 * contiguous, but instead are separated by some number of
  144: 	 * sectors.  It is specified as the ratio of physical sectors
  145: 	 * traversed per logical sector.  Thus an interleave of 1:1
  146: 	 * implies contiguous layout, while 2:1 implies that logical
  147: 	 * sector 0 is separated by one sector from logical sector 1.
  148: 	 * d_trackskew is the offset of sector 0 on track N relative to
  149: 	 * sector 0 on track N-1 on the same cylinder.  Finally, d_cylskew
  150: 	 * is the offset of sector 0 on cylinder N relative to sector 0
  151: 	 * on cylinder N-1.
  152: 	 */
  153: 	u_int16_t d_rpm;		/* rotational speed */
  154: 	u_int16_t d_interleave;		/* hardware sector interleave */
  155: 	u_int16_t d_trackskew;		/* sector 0 skew, per track */
  156: 	u_int16_t d_cylskew;		/* sector 0 skew, per cylinder */
  157: 	u_int32_t d_headswitch;		/* head switch time, usec */
  158: 	u_int32_t d_trkseek;		/* track-to-track seek, usec */
  159: 	u_int32_t d_flags;		/* generic flags */
  160: #define NDDATA 5
  161: 	u_int32_t d_drivedata[NDDATA];	/* drive-type specific information */
  162: #define NSPARE 5
  163: 	u_int32_t d_spare[NSPARE];	/* reserved for future use */
  164: 	u_int32_t d_magic2;		/* the magic number (again) */
  165: 	u_int16_t d_checksum;		/* xor of data incl. partitions */
  166: 
  167: 			/* filesystem and partition information: */
  168: 	u_int16_t d_npartitions;	/* number of partitions in following */
  169: 	u_int32_t d_bbsize;		/* size of boot area at sn0, bytes */
  170: 	u_int32_t d_sbsize;		/* max size of fs superblock, bytes */
  171: 	struct	partition {		/* the partition table */
  172: 		u_int32_t p_size;	/* number of sectors in partition */
  173: 		u_int32_t p_offset;	/* starting sector */
  174: 		u_int32_t p_fsize;	/* filesystem basic fragment size */
  175: 		u_int8_t p_fstype;	/* filesystem type, see below */
  176: 		u_int8_t p_frag;	/* filesystem fragments per block */
  177: 		union {
  178: 			u_int16_t cpg;	/* UFS: FS cylinders per group */
  179: 			u_int16_t sgs;	/* LFS: FS segment shift */
  180: 		} __partition_u1;
  181: #define	p_cpg	__partition_u1.cpg
  182: #define	p_sgs	__partition_u1.sgs
  183: 	} d_partitions[MAXPARTITIONS];	/* actually may be more */
  184: };
  185: 
  186: static u_int16_t dkcksum(struct disklabel *lp);
  187: 
  188: static __inline u_int16_t
  189: dkcksum(struct disklabel *lp)
  190: {
  191: 	u_int16_t *start, *end;
  192: 	u_int16_t sum = 0;
  193: 
  194: 	start = (u_int16_t *)lp;
  195: 	end = (u_int16_t *)&lp->d_partitions[lp->d_npartitions];
  196: 	while (start < end)
  197: 		sum ^= *start++;
  198: 	return (sum);
  199: }
  200: 
  201: #else /* LOCORE */
  202: 	/*
  203: 	 * offsets for asm boot files.
  204: 	 */
  205: 	.set	d_secsize,40
  206: 	.set	d_nsectors,44
  207: 	.set	d_ntracks,48
  208: 	.set	d_ncylinders,52
  209: 	.set	d_secpercyl,56
  210: 	.set	d_secperunit,60
  211: 	.set	d_end_,276		/* size of disk label */
  212: #endif /* LOCORE */
  213: 
  214: /* d_type values: */
  215: #define	DTYPE_SMD		1		/* SMD, XSMD; VAX hp/up */
  216: #define	DTYPE_MSCP		2		/* MSCP */
  217: #define	DTYPE_DEC		3		/* other DEC (rk, rl) */
  218: #define	DTYPE_SCSI		4		/* SCSI */
  219: #define	DTYPE_ESDI		5		/* ESDI interface */
  220: #define	DTYPE_ST506		6		/* ST506 etc. */
  221: #define	DTYPE_HPIB		7		/* CS/80 on HP-IB */
  222: #define	DTYPE_HPFL		8		/* HP Fiber-link */
  223: #define	DTYPE_FLOPPY		10		/* floppy */
  224: #define	DTYPE_CCD		11		/* concatenated disk */
  225: #define	DTYPE_VINUM		12		/* vinum volume */
  226: #define	DTYPE_DOC2K		13		/* Msys DiskOnChip */
  227: 
  228: #if defined(PC98) && !defined(PC98_ATCOMPAT)
  229: #define	DSTYPE_SEC256		0x80		/* physical sector size=256 */
  230: #endif
  231: 
  232: #ifdef DKTYPENAMES
  233: static char *dktypenames[] = {
  234: 	"unknown",
  235: 	"SMD",
  236: 	"MSCP",
  237: 	"old DEC",
  238: 	"SCSI",
  239: 	"ESDI",
  240: 	"ST506",
  241: 	"HP-IB",
  242: 	"HP-FL",
  243: 	"type 9",
  244: 	"floppy",
  245: 	"CCD",
  246: 	"Vinum",
  247: 	"DOC2K",
  248: 	NULL
  249: };
  250: #define DKMAXTYPES	(sizeof(dktypenames) / sizeof(dktypenames[0]) - 1)
  251: #endif
  252: 
  253: /*
  254:  * Filesystem type and version.
  255:  * Used to interpret other filesystem-specific
  256:  * per-partition information.
  257:  */
  258: #define	FS_UNUSED	0		/* unused */
  259: #define	FS_SWAP		1		/* swap */
  260: #define	FS_V6		2		/* Sixth Edition */
  261: #define	FS_V7		3		/* Seventh Edition */
  262: #define	FS_SYSV		4		/* System V */
  263: #define	FS_V71K		5		/* V7 with 1K blocks (4.1, 2.9) */
  264: #define	FS_V8		6		/* Eighth Edition, 4K blocks */
  265: #define	FS_BSDFFS	7		/* 4.2BSD fast file system */
  266: #define	FS_MSDOS	8		/* MSDOS file system */
  267: #define	FS_BSDLFS	9		/* 4.4BSD log-structured file system */
  268: #define	FS_OTHER	10		/* in use, but unknown/unsupported */
  269: #define	FS_HPFS		11		/* OS/2 high-performance file system */
  270: #define	FS_ISO9660	12		/* ISO 9660, normally CD-ROM */
  271: #define	FS_BOOT		13		/* partition contains bootstrap */
  272: #define	FS_VINUM	14		/* Vinum drive */
  273: 
  274: #ifdef	DKTYPENAMES
  275: static char *fstypenames[] = {
  276: 	"unused",
  277: 	"swap",
  278: 	"Version 6",
  279: 	"Version 7",
  280: 	"System V",
  281: 	"4.1BSD",
  282: 	"Eighth Edition",
  283: 	"4.2BSD",
  284: 	"MSDOS",
  285: 	"4.4LFS",
  286: 	"unknown",
  287: 	"HPFS",
  288: 	"ISO9660",
  289: 	"boot",
  290: 	"vinum",
  291: 	NULL
  292: };
  293: #define FSMAXTYPES	(sizeof(fstypenames) / sizeof(fstypenames[0]) - 1)
  294: #endif
  295: 
  296: /*
  297:  * flags shared by various drives:
  298:  */
  299: #define		D_REMOVABLE	0x01		/* removable media */
  300: #define		D_ECC		0x02		/* supports ECC */
  301: #define		D_BADSECT	0x04		/* supports bad sector forw. */
  302: #define		D_RAMDISK	0x08		/* disk emulator */
  303: #define		D_CHAIN		0x10		/* can do back-back transfers */
  304: 
  305: /*
  306:  * Drive data for SMD.
  307:  */
  308: #define	d_smdflags	d_drivedata[0]
  309: #define		D_SSE		0x1		/* supports skip sectoring */
  310: #define	d_mindist	d_drivedata[1]
  311: #define	d_maxdist	d_drivedata[2]
  312: #define	d_sdist		d_drivedata[3]
  313: 
  314: /*
  315:  * Drive data for ST506.
  316:  */
  317: #define d_precompcyl	d_drivedata[0]
  318: #define d_gap3		d_drivedata[1]		/* used only when formatting */
  319: 
  320: /*
  321:  * Drive data for SCSI.
  322:  */
  323: #define	d_blind		d_drivedata[0]
  324: 
  325: #ifndef LOCORE
  326: /*
  327:  * Structure used to perform a format or other raw operation, returning
  328:  * data and/or register values.  Register identification and format
  329:  * are device- and driver-dependent.
  330:  */
  331: struct format_op {
  332: 	char	*df_buf;
  333: 	int	 df_count;		/* value-result */
  334: 	daddr_t	 df_startblk;
  335: 	int	 df_reg[8];		/* result */
  336: };
  337: 
  338: /*
  339:  * Structure used internally to retrieve information about a partition
  340:  * on a disk.
  341:  */
  342: struct partinfo {
  343: 	struct disklabel *disklab;
  344: 	struct partition *part;
  345: };
  346: 
  347: /*
  348:  * Disk-specific ioctls.
  349:  */
  350: 		/* get and set disklabel; DIOCGPART used internally */
  351: #define DIOCGDINFO	_IOR('d', 101, struct disklabel)/* get */
  352: #define DIOCSDINFO	_IOW('d', 102, struct disklabel)/* set */
  353: #define DIOCWDINFO	_IOW('d', 103, struct disklabel)/* set, update disk */
  354: #define DIOCGPART	_IOW('d', 104, struct partinfo)	/* get partition */
  355: #define DIOCGDVIRGIN	_IOR('d', 105, struct disklabel) /* get virgin label */
  356: 
  357: #define DIOCWLABEL	_IOW('d', 109, int)	/* write en/disable label */
  358: 
  359: #ifdef _KERNEL
  360: 
  361: /*
  362:  * XXX encoding of disk minor numbers, should be elsewhere.
  363:  *
  364:  * See <sys/reboot.h> for a possibly better encoding.
  365:  *
  366:  * "cpio -H newc" can be used to back up device files with large minor
  367:  * numbers (but not ones >= 2^31).  Old cpio formats and all tar formats
  368:  * don't have enough bits, and cpio and tar don't notice the lossage.
  369:  * There are also some sign extension bugs.
  370:  */
  371: 
  372: /*
  373:        3                   2                   1                   0
  374:      1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
  375:     _________________________________________________________________
  376:     | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
  377:     -----------------------------------------------------------------
  378:     |    TYPE     |UNIT_2 |P| SLICE |  MAJOR?       |  UNIT   |PART |
  379:     -----------------------------------------------------------------
  380: */
  381: 
  382: #define DKMAXUNIT 0x1ff		/* Highest disk unit number */
  383: 
  384: #define	dkmakeminor(unit, slice, part) \
  385: 				(((slice) << 16) | (((unit) & 0x1e0) << 16) | \
  386: 				(((unit) & 0x1f) << 3) | (part & 7) | \
  387: 				((part & 0x08) << 17))
  388: 
  389: static __inline u_int
  390: dkunitmask(void)
  391: {
  392: 	return (0x01e000f8);
  393: }
  394: 
  395: static __inline u_int
  396: dkmakeunit(int unit)
  397: {
  398: 	return(dkmakeminor(unit, 0, 0));
  399: }
  400: 
  401: static __inline dev_t
  402: dkmodpart(dev_t dev, int part)
  403: {
  404: 	int val;
  405: 
  406: 	if (part < 8)
  407: 		val = (part & 7);
  408: 	else
  409: 		val = (part & 7) | 0x100000;
  410: 	return (make_sub_dev(dev, (minor(dev) & ~0x100007) | val));
  411: }
  412: 
  413: static __inline dev_t
  414: dkmodslice(dev_t dev, int slice)
  415: {
  416: 	return (make_sub_dev(dev, (minor(dev) & ~0x0f0000) | (slice << 16)));
  417: }
  418: 
  419: static __inline int
  420: dkpart(dev_t dev)
  421: {
  422: 	return (((minor(dev) >> 17) & 0x08) | (minor(dev) & 7));
  423: }
  424: 
  425: #define	dkslice(dev)		((minor(dev) >> 16) & 0x0f)
  426: #define	dktype(dev)       	((minor(dev) >> 25) & 0x7f)
  427: 
  428: static __inline u_int
  429: dkunit(dev_t dev)
  430: {
  431: 	return (((minor(dev) >> 16) & 0x1e0) | ((minor(dev) >> 3) & 0x1f));
  432: }
  433: 
  434: struct	buf;
  435: struct	buf_queue_head;
  436: 
  437: int	bounds_check_with_label (struct buf *bp, struct disklabel *lp,
  438: 				     int wlabel);
  439: void	diskerr (struct buf *bp, char *what, int pri, int blkdone,
  440: 		     struct disklabel *lp);
  441: void	disksort (struct buf *ap, struct buf *bp);
  442: char	*readdisklabel (dev_t dev, struct disklabel *lp);
  443: void	bufqdisksort (struct buf_queue_head *ap, struct buf *bp);
  444: int	setdisklabel (struct disklabel *olp, struct disklabel *nlp,
  445: 			  u_long openmask);
  446: int	writedisklabel (dev_t dev, struct disklabel *lp);
  447: #ifdef __alpha__
  448: void	alpha_fix_srm_checksum (struct buf *bp);
  449: #endif
  450: 
  451: #endif /* _KERNEL */
  452: 
  453: #endif /* LOCORE */
  454: 
  455: #ifndef _KERNEL
  456: __BEGIN_DECLS
  457: struct disklabel *getdiskbyname (const char *);
  458: __END_DECLS
  459: #endif
  460: 
  461: #endif /* !_SYS_DISKLABEL_H_ */