[U-Boot] [PATCH 09/11 v4] UBI: Add basic UBI support to U-Boot (Part 8/8)
Stefan Roese
sr at denx.de
Wed Nov 19 20:39:38 CET 2008
From: Kyungmin Park <kyungmin.park at samsung.com>
This patch adds basic UBI (Unsorted Block Image) support to U-Boot.
It's based on the Linux UBI version and basically has a "OS"
translation wrapper that defines most Linux specific calls
(spin_lock() etc.) into no-ops. Some source code parts have been
uncommented by "#ifdef UBI_LINUX". This makes it easier to compare
this version with the Linux version and simplifies future UBI
ports/bug-fixes from the Linux version.
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
Signed-off-by: Stefan Roese <sr at denx.de>
---
Makefile | 1 +
include/linux/mtd/ubi-header.h | 360 ----------------------------------------
include/linux/mtd/ubi-user.h | 161 ------------------
3 files changed, 1 insertions(+), 521 deletions(-)
delete mode 100644 include/linux/mtd/ubi-header.h
delete mode 100644 include/linux/mtd/ubi-user.h
diff --git a/Makefile b/Makefile
index fd521b6..befb608 100644
--- a/Makefile
+++ b/Makefile
@@ -230,6 +230,7 @@ LIBS += drivers/mtd/libmtd.a
LIBS += drivers/mtd/nand/libnand.a
LIBS += drivers/mtd/nand_legacy/libnand_legacy.a
LIBS += drivers/mtd/onenand/libonenand.a
+LIBS += drivers/mtd/ubi/libubi.a
LIBS += drivers/mtd/spi/libspi_flash.a
LIBS += drivers/net/libnet.a
LIBS += drivers/net/phy/libphy.a
diff --git a/include/linux/mtd/ubi-header.h b/include/linux/mtd/ubi-header.h
deleted file mode 100644
index fa479c7..0000000
--- a/include/linux/mtd/ubi-header.h
+++ /dev/null
@@ -1,360 +0,0 @@
-/*
- * Copyright (c) International Business Machines Corp., 2006
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
- * the GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
- *
- * Authors: Artem Bityutskiy (Битюцкий Ðртём)
- * Thomas Gleixner
- * Frank Haverkamp
- * Oliver Lohmann
- * Andreas Arnez
- */
-
-/*
- * This file defines the layout of UBI headers and all the other UBI on-flash
- * data structures. May be included by user-space.
- */
-
-#ifndef __UBI_HEADER_H__
-#define __UBI_HEADER_H__
-
-#include <asm/byteorder.h>
-
-/* The version of UBI images supported by this implementation */
-#define UBI_VERSION 1
-
-/* The highest erase counter value supported by this implementation */
-#define UBI_MAX_ERASECOUNTER 0x7FFFFFFF
-
-/* The initial CRC32 value used when calculating CRC checksums */
-#define UBI_CRC32_INIT 0xFFFFFFFFU
-
-/* Erase counter header magic number (ASCII "UBI#") */
-#define UBI_EC_HDR_MAGIC 0x55424923
-/* Volume identifier header magic number (ASCII "UBI!") */
-#define UBI_VID_HDR_MAGIC 0x55424921
-
-/*
- * Volume type constants used in the volume identifier header.
- *
- * @UBI_VID_DYNAMIC: dynamic volume
- * @UBI_VID_STATIC: static volume
- */
-enum {
- UBI_VID_DYNAMIC = 1,
- UBI_VID_STATIC = 2
-};
-
-/*
- * Compatibility constants used by internal volumes.
- *
- * @UBI_COMPAT_DELETE: delete this internal volume before anything is written
- * to the flash
- * @UBI_COMPAT_RO: attach this device in read-only mode
- * @UBI_COMPAT_PRESERVE: preserve this internal volume - do not touch its
- * physical eraseblocks, don't allow the wear-leveling unit to move them
- * @UBI_COMPAT_REJECT: reject this UBI image
- */
-enum {
- UBI_COMPAT_DELETE = 1,
- UBI_COMPAT_RO = 2,
- UBI_COMPAT_PRESERVE = 4,
- UBI_COMPAT_REJECT = 5
-};
-
-/*
- * ubi16_t/ubi32_t/ubi64_t - 16, 32, and 64-bit integers used in UBI on-flash
- * data structures.
- */
-typedef struct {
- uint16_t int16;
-} __attribute__ ((packed)) ubi16_t;
-
-typedef struct {
- uint32_t int32;
-} __attribute__ ((packed)) ubi32_t;
-
-typedef struct {
- uint64_t int64;
-} __attribute__ ((packed)) ubi64_t;
-
-/*
- * In this implementation of UBI uses the big-endian format for on-flash
- * integers. The below are the corresponding conversion macros.
- */
-#define cpu_to_ubi16(x) ((ubi16_t){__cpu_to_be16(x)})
-#define ubi16_to_cpu(x) ((uint16_t)__be16_to_cpu((x).int16))
-
-#define cpu_to_ubi32(x) ((ubi32_t){__cpu_to_be32(x)})
-#define ubi32_to_cpu(x) ((uint32_t)__be32_to_cpu((x).int32))
-
-#define cpu_to_ubi64(x) ((ubi64_t){__cpu_to_be64(x)})
-#define ubi64_to_cpu(x) ((uint64_t)__be64_to_cpu((x).int64))
-
-/* Sizes of UBI headers */
-#define UBI_EC_HDR_SIZE sizeof(struct ubi_ec_hdr)
-#define UBI_VID_HDR_SIZE sizeof(struct ubi_vid_hdr)
-
-/* Sizes of UBI headers without the ending CRC */
-#define UBI_EC_HDR_SIZE_CRC (UBI_EC_HDR_SIZE - sizeof(ubi32_t))
-#define UBI_VID_HDR_SIZE_CRC (UBI_VID_HDR_SIZE - sizeof(ubi32_t))
-
-/**
- * struct ubi_ec_hdr - UBI erase counter header.
- * @magic: erase counter header magic number (%UBI_EC_HDR_MAGIC)
- * @version: version of UBI implementation which is supposed to accept this
- * UBI image
- * @padding1: reserved for future, zeroes
- * @ec: the erase counter
- * @vid_hdr_offset: where the VID header starts
- * @data_offset: where the user data start
- * @padding2: reserved for future, zeroes
- * @hdr_crc: erase counter header CRC checksum
- *
- * The erase counter header takes 64 bytes and has a plenty of unused space for
- * future usage. The unused fields are zeroed. The @version field is used to
- * indicate the version of UBI implementation which is supposed to be able to
- * work with this UBI image. If @version is greater then the current UBI
- * version, the image is rejected. This may be useful in future if something
- * is changed radically. This field is duplicated in the volume identifier
- * header.
- *
- * The @vid_hdr_offset and @data_offset fields contain the offset of the the
- * volume identifier header and user data, relative to the beginning of the
- * physical eraseblock. These values have to be the same for all physical
- * eraseblocks.
- */
-struct ubi_ec_hdr {
- ubi32_t magic;
- uint8_t version;
- uint8_t padding1[3];
- ubi64_t ec; /* Warning: the current limit is 31-bit anyway! */
- ubi32_t vid_hdr_offset;
- ubi32_t data_offset;
- uint8_t padding2[36];
- ubi32_t hdr_crc;
-} __attribute__ ((packed));
-
-/**
- * struct ubi_vid_hdr - on-flash UBI volume identifier header.
- * @magic: volume identifier header magic number (%UBI_VID_HDR_MAGIC)
- * @version: UBI implementation version which is supposed to accept this UBI
- * image (%UBI_VERSION)
- * @vol_type: volume type (%UBI_VID_DYNAMIC or %UBI_VID_STATIC)
- * @copy_flag: if this logical eraseblock was copied from another physical
- * eraseblock (for wear-leveling reasons)
- * @compat: compatibility of this volume (%0, %UBI_COMPAT_DELETE,
- * %UBI_COMPAT_IGNORE, %UBI_COMPAT_PRESERVE, or %UBI_COMPAT_REJECT)
- * @vol_id: ID of this volume
- * @lnum: logical eraseblock number
- * @leb_ver: version of this logical eraseblock (IMPORTANT: obsolete, to be
- * removed, kept only for not breaking older UBI users)
- * @data_size: how many bytes of data this logical eraseblock contains
- * @used_ebs: total number of used logical eraseblocks in this volume
- * @data_pad: how many bytes at the end of this physical eraseblock are not
- * used
- * @data_crc: CRC checksum of the data stored in this logical eraseblock
- * @padding1: reserved for future, zeroes
- * @sqnum: sequence number
- * @padding2: reserved for future, zeroes
- * @hdr_crc: volume identifier header CRC checksum
- *
- * The @sqnum is the value of the global sequence counter at the time when this
- * VID header was created. The global sequence counter is incremented each time
- * UBI writes a new VID header to the flash, i.e. when it maps a logical
- * eraseblock to a new physical eraseblock. The global sequence counter is an
- * unsigned 64-bit integer and we assume it never overflows. The @sqnum
- * (sequence number) is used to distinguish between older and newer versions of
- * logical eraseblocks.
- *
- * There are 2 situations when there may be more then one physical eraseblock
- * corresponding to the same logical eraseblock, i.e., having the same @vol_id
- * and @lnum values in the volume identifier header. Suppose we have a logical
- * eraseblock L and it is mapped to the physical eraseblock P.
- *
- * 1. Because UBI may erase physical eraseblocks asynchronously, the following
- * situation is possible: L is asynchronously erased, so P is scheduled for
- * erasure, then L is written to,i.e. mapped to another physical eraseblock P1,
- * so P1 is written to, then an unclean reboot happens. Result - there are 2
- * physical eraseblocks P and P1 corresponding to the same logical eraseblock
- * L. But P1 has greater sequence number, so UBI picks P1 when it attaches the
- * flash.
- *
- * 2. From time to time UBI moves logical eraseblocks to other physical
- * eraseblocks for wear-leveling reasons. If, for example, UBI moves L from P
- * to P1, and an unclean reboot happens before P is physically erased, there
- * are two physical eraseblocks P and P1 corresponding to L and UBI has to
- * select one of them when the flash is attached. The @sqnum field says which
- * PEB is the original (obviously P will have lower @sqnum) and the copy. But
- * it is not enough to select the physical eraseblock with the higher sequence
- * number, because the unclean reboot could have happen in the middle of the
- * copying process, so the data in P is corrupted. It is also not enough to
- * just select the physical eraseblock with lower sequence number, because the
- * data there may be old (consider a case if more data was added to P1 after
- * the copying). Moreover, the unclean reboot may happen when the erasure of P
- * was just started, so it result in unstable P, which is "mostly" OK, but
- * still has unstable bits.
- *
- * UBI uses the @copy_flag field to indicate that this logical eraseblock is a
- * copy. UBI also calculates data CRC when the data is moved and stores it at
- * the @data_crc field of the copy (P1). So when UBI needs to pick one physical
- * eraseblock of two (P or P1), the @copy_flag of the newer one (P1) is
- * examined. If it is cleared, the situation* is simple and the newer one is
- * picked. If it is set, the data CRC of the copy (P1) is examined. If the CRC
- * checksum is correct, this physical eraseblock is selected (P1). Otherwise
- * the older one (P) is selected.
- *
- * Note, there is an obsolete @leb_ver field which was used instead of @sqnum
- * in the past. But it is not used anymore and we keep it in order to be able
- * to deal with old UBI images. It will be removed at some point.
- *
- * There are 2 sorts of volumes in UBI: user volumes and internal volumes.
- * Internal volumes are not seen from outside and are used for various internal
- * UBI purposes. In this implementation there is only one internal volume - the
- * layout volume. Internal volumes are the main mechanism of UBI extensions.
- * For example, in future one may introduce a journal internal volume. Internal
- * volumes have their own reserved range of IDs.
- *
- * The @compat field is only used for internal volumes and contains the "degree
- * of their compatibility". It is always zero for user volumes. This field
- * provides a mechanism to introduce UBI extensions and to be still compatible
- * with older UBI binaries. For example, if someone introduced a journal in
- * future, he would probably use %UBI_COMPAT_DELETE compatibility for the
- * journal volume. And in this case, older UBI binaries, which know nothing
- * about the journal volume, would just delete this volume and work perfectly
- * fine. This is similar to what Ext2fs does when it is fed by an Ext3fs image
- * - it just ignores the Ext3fs journal.
- *
- * The @data_crc field contains the CRC checksum of the contents of the logical
- * eraseblock if this is a static volume. In case of dynamic volumes, it does
- * not contain the CRC checksum as a rule. The only exception is when the
- * data of the physical eraseblock was moved by the wear-leveling unit, then
- * the wear-leveling unit calculates the data CRC and stores it in the
- * @data_crc field. And of course, the @copy_flag is %in this case.
- *
- * The @data_size field is used only for static volumes because UBI has to know
- * how many bytes of data are stored in this eraseblock. For dynamic volumes,
- * this field usually contains zero. The only exception is when the data of the
- * physical eraseblock was moved to another physical eraseblock for
- * wear-leveling reasons. In this case, UBI calculates CRC checksum of the
- * contents and uses both @data_crc and @data_size fields. In this case, the
- * @data_size field contains data size.
- *
- * The @used_ebs field is used only for static volumes and indicates how many
- * eraseblocks the data of the volume takes. For dynamic volumes this field is
- * not used and always contains zero.
- *
- * The @data_pad is calculated when volumes are created using the alignment
- * parameter. So, effectively, the @data_pad field reduces the size of logical
- * eraseblocks of this volume. This is very handy when one uses block-oriented
- * software (say, cramfs) on top of the UBI volume.
- */
-struct ubi_vid_hdr {
- ubi32_t magic;
- uint8_t version;
- uint8_t vol_type;
- uint8_t copy_flag;
- uint8_t compat;
- ubi32_t vol_id;
- ubi32_t lnum;
- ubi32_t leb_ver; /* obsolete, to be removed, don't use */
- ubi32_t data_size;
- ubi32_t used_ebs;
- ubi32_t data_pad;
- ubi32_t data_crc;
- uint8_t padding1[4];
- ubi64_t sqnum;
- uint8_t padding2[12];
- ubi32_t hdr_crc;
-} __attribute__ ((packed));
-
-/* Internal UBI volumes count */
-#define UBI_INT_VOL_COUNT 1
-
-/*
- * Starting ID of internal volumes. There is reserved room for 4096 internal
- * volumes.
- */
-#define UBI_INTERNAL_VOL_START (0x7FFFFFFF - 4096)
-
-/* The layout volume contains the volume table */
-
-#define UBI_LAYOUT_VOL_ID UBI_INTERNAL_VOL_START
-#define UBI_LAYOUT_VOLUME_EBS 2
-#define UBI_LAYOUT_VOLUME_NAME "layout volume"
-#define UBI_LAYOUT_VOLUME_COMPAT UBI_COMPAT_REJECT
-
-/* The maximum number of volumes per one UBI device */
-#define UBI_MAX_VOLUMES 128
-
-/* The maximum volume name length */
-#define UBI_VOL_NAME_MAX 127
-
-/* Size of the volume table record */
-#define UBI_VTBL_RECORD_SIZE sizeof(struct ubi_vtbl_record)
-
-/* Size of the volume table record without the ending CRC */
-#define UBI_VTBL_RECORD_SIZE_CRC (UBI_VTBL_RECORD_SIZE - sizeof(ubi32_t))
-
-/**
- * struct ubi_vtbl_record - a record in the volume table.
- * @reserved_pebs: how many physical eraseblocks are reserved for this volume
- * @alignment: volume alignment
- * @data_pad: how many bytes are unused at the end of the each physical
- * eraseblock to satisfy the requested alignment
- * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
- * @upd_marker: if volume update was started but not finished
- * @name_len: volume name length
- * @name: the volume name
- * @padding2: reserved, zeroes
- * @crc: a CRC32 checksum of the record
- *
- * The volume table records are stored in the volume table, which is stored in
- * the layout volume. The layout volume consists of 2 logical eraseblock, each
- * of which contains a copy of the volume table (i.e., the volume table is
- * duplicated). The volume table is an array of &struct ubi_vtbl_record
- * objects indexed by the volume ID.
- *
- * If the size of the logical eraseblock is large enough to fit
- * %UBI_MAX_VOLUMES records, the volume table contains %UBI_MAX_VOLUMES
- * records. Otherwise, it contains as many records as it can fit (i.e., size of
- * logical eraseblock divided by sizeof(struct ubi_vtbl_record)).
- *
- * The @upd_marker flag is used to implement volume update. It is set to %1
- * before update and set to %0 after the update. So if the update operation was
- * interrupted, UBI knows that the volume is corrupted.
- *
- * The @alignment field is specified when the volume is created and cannot be
- * later changed. It may be useful, for example, when a block-oriented file
- * system works on top of UBI. The @data_pad field is calculated using the
- * logical eraseblock size and @alignment. The alignment must be multiple to the
- * minimal flash I/O unit. If @alignment is 1, all the available space of
- * the physical eraseblocks is used.
- *
- * Empty records contain all zeroes and the CRC checksum of those zeroes.
- */
-struct ubi_vtbl_record {
- ubi32_t reserved_pebs;
- ubi32_t alignment;
- ubi32_t data_pad;
- uint8_t vol_type;
- uint8_t upd_marker;
- ubi16_t name_len;
- uint8_t name[UBI_VOL_NAME_MAX+1];
- uint8_t padding2[24];
- ubi32_t crc;
-} __attribute__ ((packed));
-
-#endif /* !__UBI_HEADER_H__ */
diff --git a/include/linux/mtd/ubi-user.h b/include/linux/mtd/ubi-user.h
deleted file mode 100644
index fe06ded..0000000
--- a/include/linux/mtd/ubi-user.h
+++ /dev/null
@@ -1,161 +0,0 @@
-/*
- * Copyright (c) International Business Machines Corp., 2006
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
- * the GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
- *
- * Author: Artem Bityutskiy (Битюцкий Ðртём)
- */
-
-#ifndef __UBI_USER_H__
-#define __UBI_USER_H__
-
-/*
- * UBI volume creation
- * ~~~~~~~~~~~~~~~~~~~
- *
- * UBI volumes are created via the %UBI_IOCMKVOL IOCTL command of UBI character
- * device. A &struct ubi_mkvol_req object has to be properly filled and a
- * pointer to it has to be passed to the IOCTL.
- *
- * UBI volume deletion
- * ~~~~~~~~~~~~~~~~~~~
- *
- * To delete a volume, the %UBI_IOCRMVOL IOCTL command of the UBI character
- * device should be used. A pointer to the 32-bit volume ID hast to be passed
- * to the IOCTL.
- *
- * UBI volume re-size
- * ~~~~~~~~~~~~~~~~~~
- *
- * To re-size a volume, the %UBI_IOCRSVOL IOCTL command of the UBI character
- * device should be used. A &struct ubi_rsvol_req object has to be properly
- * filled and a pointer to it has to be passed to the IOCTL.
- *
- * UBI volume update
- * ~~~~~~~~~~~~~~~~~
- *
- * Volume update should be done via the %UBI_IOCVOLUP IOCTL command of the
- * corresponding UBI volume character device. A pointer to a 64-bit update
- * size should be passed to the IOCTL. After then, UBI expects user to write
- * this number of bytes to the volume character device. The update is finished
- * when the claimed number of bytes is passed. So, the volume update sequence
- * is something like:
- *
- * fd = open("/dev/my_volume");
- * ioctl(fd, UBI_IOCVOLUP, &image_size);
- * write(fd, buf, image_size);
- * close(fd);
- */
-
-/*
- * When a new volume is created, users may either specify the volume number they
- * want to create or to let UBI automatically assign a volume number using this
- * constant.
- */
-#define UBI_VOL_NUM_AUTO (-1)
-
-/* Maximum volume name length */
-#define UBI_MAX_VOLUME_NAME 127
-
-/* IOCTL commands of UBI character devices */
-
-#define UBI_IOC_MAGIC 'o'
-
-/* Create an UBI volume */
-#define UBI_IOCMKVOL _IOW(UBI_IOC_MAGIC, 0, struct ubi_mkvol_req)
-/* Remove an UBI volume */
-#define UBI_IOCRMVOL _IOW(UBI_IOC_MAGIC, 1, int32_t)
-/* Re-size an UBI volume */
-#define UBI_IOCRSVOL _IOW(UBI_IOC_MAGIC, 2, struct ubi_rsvol_req)
-
-/* IOCTL commands of UBI volume character devices */
-
-#define UBI_VOL_IOC_MAGIC 'O'
-
-/* Start UBI volume update */
-#define UBI_IOCVOLUP _IOW(UBI_VOL_IOC_MAGIC, 0, int64_t)
-/* An eraseblock erasure command, used for debugging, disabled by default */
-#define UBI_IOCEBER _IOW(UBI_VOL_IOC_MAGIC, 1, int32_t)
-
-/*
- * UBI volume type constants.
- *
- * @UBI_DYNAMIC_VOLUME: dynamic volume
- * @UBI_STATIC_VOLUME: static volume
- */
-enum {
- UBI_DYNAMIC_VOLUME = 3,
- UBI_STATIC_VOLUME = 4
-};
-
-/**
- * struct ubi_mkvol_req - volume description data structure used in
- * volume creation requests.
- * @vol_id: volume number
- * @alignment: volume alignment
- * @bytes: volume size in bytes
- * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
- * @padding1: reserved for future, not used
- * @name_len: volume name length
- * @padding2: reserved for future, not used
- * @name: volume name
- *
- * This structure is used by userspace programs when creating new volumes. The
- * @used_bytes field is only necessary when creating static volumes.
- *
- * The @alignment field specifies the required alignment of the volume logical
- * eraseblock. This means, that the size of logical eraseblocks will be aligned
- * to this number, i.e.,
- * (UBI device logical eraseblock size) mod (@alignment) = 0.
- *
- * To put it differently, the logical eraseblock of this volume may be slightly
- * shortened in order to make it properly aligned. The alignment has to be
- * multiple of the flash minimal input/output unit, or %1 to utilize the entire
- * available space of logical eraseblocks.
- *
- * The @alignment field may be useful, for example, when one wants to maintain
- * a block device on top of an UBI volume. In this case, it is desirable to fit
- * an integer number of blocks in logical eraseblocks of this UBI volume. With
- * alignment it is possible to update this volume using plane UBI volume image
- * BLOBs, without caring about how to properly align them.
- */
-struct ubi_mkvol_req {
- int32_t vol_id;
- int32_t alignment;
- int64_t bytes;
- int8_t vol_type;
- int8_t padding1;
- int16_t name_len;
- int8_t padding2[4];
- char name[UBI_MAX_VOLUME_NAME+1];
-} __attribute__ ((packed));
-
-/**
- * struct ubi_rsvol_req - a data structure used in volume re-size requests.
- * @vol_id: ID of the volume to re-size
- * @bytes: new size of the volume in bytes
- *
- * Re-sizing is possible for both dynamic and static volumes. But while dynamic
- * volumes may be re-sized arbitrarily, static volumes cannot be made to be
- * smaller then the number of bytes they bear. To arbitrarily shrink a static
- * volume, it must be wiped out first (by means of volume update operation with
- * zero number of bytes).
- */
-struct ubi_rsvol_req {
- int64_t bytes;
- int32_t vol_id;
-} __attribute__ ((packed));
-
-#endif /* __UBI_USER_H__ */
--
1.6.0.4
More information about the U-Boot
mailing list