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![Eric Nelson](/assets/img/avatar_default.png)
Add a block device cache to speed up repeated reads of block devices by
various filesystems.
This small amount of cache can dramatically speed up filesystem
operations by skipping repeated reads of common areas of a block
device (typically directory structures).
This has shown to have some benefit on FAT filesystem operations of
loading a kernel and RAM disk, but more dramatic benefits on ext4
filesystems when the kernel and/or RAM disk are spread across
multiple extent header structures as described in commit fc0fc50
.
The cache is implemented through a minimal list (block_cache) maintained
in most-recently-used order and count of the current number of entries
(cache_count). It uses a maximum block count setting to prevent copies
of large block reads and an upper bound on the number of cached areas.
The maximum number of entries in the cache defaults to 32 and the maximum
number of blocks per cache entry has a default of 2, which has shown to
produce the best results on testing of ext4 and FAT filesystems.
The 'blkcache' command (enabled through CONFIG_CMD_BLOCK_CACHE) allows
changing these values and can be used to tune for a particular filesystem
layout.
Signed-off-by: Eric Nelson <eric@nelint.com>
352 lines
9.9 KiB
C
352 lines
9.9 KiB
C
/*
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* (C) Copyright 2000-2004
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* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#ifndef BLK_H
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#define BLK_H
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#ifdef CONFIG_SYS_64BIT_LBA
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typedef uint64_t lbaint_t;
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#define LBAFlength "ll"
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#else
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typedef ulong lbaint_t;
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#define LBAFlength "l"
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#endif
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#define LBAF "%" LBAFlength "x"
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#define LBAFU "%" LBAFlength "u"
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/* Interface types: */
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enum if_type {
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IF_TYPE_UNKNOWN = 0,
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IF_TYPE_IDE,
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IF_TYPE_SCSI,
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IF_TYPE_ATAPI,
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IF_TYPE_USB,
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IF_TYPE_DOC,
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IF_TYPE_MMC,
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IF_TYPE_SD,
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IF_TYPE_SATA,
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IF_TYPE_HOST,
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IF_TYPE_COUNT, /* Number of interface types */
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};
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/*
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* With driver model (CONFIG_BLK) this is uclass platform data, accessible
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* with dev_get_uclass_platdata(dev)
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*/
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struct blk_desc {
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/*
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* TODO: With driver model we should be able to use the parent
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* device's uclass instead.
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*/
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enum if_type if_type; /* type of the interface */
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int devnum; /* device number */
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unsigned char part_type; /* partition type */
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unsigned char target; /* target SCSI ID */
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unsigned char lun; /* target LUN */
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unsigned char hwpart; /* HW partition, e.g. for eMMC */
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unsigned char type; /* device type */
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unsigned char removable; /* removable device */
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#ifdef CONFIG_LBA48
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/* device can use 48bit addr (ATA/ATAPI v7) */
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unsigned char lba48;
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#endif
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lbaint_t lba; /* number of blocks */
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unsigned long blksz; /* block size */
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int log2blksz; /* for convenience: log2(blksz) */
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char vendor[40+1]; /* IDE model, SCSI Vendor */
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char product[20+1]; /* IDE Serial no, SCSI product */
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char revision[8+1]; /* firmware revision */
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#ifdef CONFIG_BLK
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struct udevice *bdev;
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#else
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unsigned long (*block_read)(struct blk_desc *block_dev,
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lbaint_t start,
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lbaint_t blkcnt,
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void *buffer);
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unsigned long (*block_write)(struct blk_desc *block_dev,
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lbaint_t start,
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lbaint_t blkcnt,
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const void *buffer);
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unsigned long (*block_erase)(struct blk_desc *block_dev,
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lbaint_t start,
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lbaint_t blkcnt);
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void *priv; /* driver private struct pointer */
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#endif
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};
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#define BLOCK_CNT(size, blk_desc) (PAD_COUNT(size, blk_desc->blksz))
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#define PAD_TO_BLOCKSIZE(size, blk_desc) \
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(PAD_SIZE(size, blk_desc->blksz))
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#ifdef CONFIG_BLOCK_CACHE
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/**
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* blkcache_read() - attempt to read a set of blocks from cache
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*
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* @param iftype - IF_TYPE_x for type of device
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* @param dev - device index of particular type
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* @param start - starting block number
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* @param blkcnt - number of blocks to read
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* @param blksz - size in bytes of each block
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* @param buf - buffer to contain cached data
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*
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* @return - '1' if block returned from cache, '0' otherwise.
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*/
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int blkcache_read
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(int iftype, int dev,
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lbaint_t start, lbaint_t blkcnt,
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unsigned long blksz, void *buffer);
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/**
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* blkcache_fill() - make data read from a block device available
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* to the block cache
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*
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* @param iftype - IF_TYPE_x for type of device
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* @param dev - device index of particular type
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* @param start - starting block number
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* @param blkcnt - number of blocks available
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* @param blksz - size in bytes of each block
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* @param buf - buffer containing data to cache
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*
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*/
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void blkcache_fill
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(int iftype, int dev,
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lbaint_t start, lbaint_t blkcnt,
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unsigned long blksz, void const *buffer);
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/**
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* blkcache_invalidate() - discard the cache for a set of blocks
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* because of a write or device (re)initialization.
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*
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* @param iftype - IF_TYPE_x for type of device
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* @param dev - device index of particular type
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*/
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void blkcache_invalidate
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(int iftype, int dev);
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/**
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* blkcache_configure() - configure block cache
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*
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* @param blocks - maximum blocks per entry
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* @param entries - maximum entries in cache
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*/
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void blkcache_configure(unsigned blocks, unsigned entries);
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/*
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* statistics of the block cache
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*/
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struct block_cache_stats {
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unsigned hits;
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unsigned misses;
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unsigned entries; /* current entry count */
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unsigned max_blocks_per_entry;
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unsigned max_entries;
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};
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/**
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* get_blkcache_stats() - return statistics and reset
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*
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* @param stats - statistics are copied here
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*/
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void blkcache_stats(struct block_cache_stats *stats);
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#else
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static inline int blkcache_read
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(int iftype, int dev,
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lbaint_t start, lbaint_t blkcnt,
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unsigned long blksz, void *buffer)
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{
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return 0;
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}
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static inline void blkcache_fill
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(int iftype, int dev,
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lbaint_t start, lbaint_t blkcnt,
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unsigned long blksz, void const *buffer) {}
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static inline void blkcache_invalidate
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(int iftype, int dev) {}
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#endif
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#ifdef CONFIG_BLK
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struct udevice;
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/* Operations on block devices */
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struct blk_ops {
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/**
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* read() - read from a block device
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*
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* @dev: Device to read from
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* @start: Start block number to read (0=first)
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* @blkcnt: Number of blocks to read
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* @buffer: Destination buffer for data read
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* @return number of blocks read, or -ve error number (see the
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* IS_ERR_VALUE() macro
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*/
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unsigned long (*read)(struct udevice *dev, lbaint_t start,
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lbaint_t blkcnt, void *buffer);
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/**
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* write() - write to a block device
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*
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* @dev: Device to write to
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* @start: Start block number to write (0=first)
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* @blkcnt: Number of blocks to write
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* @buffer: Source buffer for data to write
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* @return number of blocks written, or -ve error number (see the
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* IS_ERR_VALUE() macro
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*/
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unsigned long (*write)(struct udevice *dev, lbaint_t start,
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lbaint_t blkcnt, const void *buffer);
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/**
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* erase() - erase a section of a block device
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*
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* @dev: Device to (partially) erase
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* @start: Start block number to erase (0=first)
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* @blkcnt: Number of blocks to erase
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* @return number of blocks erased, or -ve error number (see the
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* IS_ERR_VALUE() macro
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*/
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unsigned long (*erase)(struct udevice *dev, lbaint_t start,
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lbaint_t blkcnt);
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};
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#define blk_get_ops(dev) ((struct blk_ops *)(dev)->driver->ops)
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/*
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* These functions should take struct udevice instead of struct blk_desc,
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* but this is convenient for migration to driver model. Add a 'd' prefix
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* to the function operations, so that blk_read(), etc. can be reserved for
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* functions with the correct arguments.
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*/
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unsigned long blk_dread(struct blk_desc *block_dev, lbaint_t start,
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lbaint_t blkcnt, void *buffer);
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unsigned long blk_dwrite(struct blk_desc *block_dev, lbaint_t start,
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lbaint_t blkcnt, const void *buffer);
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unsigned long blk_derase(struct blk_desc *block_dev, lbaint_t start,
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lbaint_t blkcnt);
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/**
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* blk_get_device() - Find and probe a block device ready for use
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*
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* @if_type: Interface type (enum if_type_t)
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* @devnum: Device number (specific to each interface type)
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* @devp: the device, if found
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* @return - if found, -ENODEV if no device found, or other -ve error value
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*/
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int blk_get_device(int if_type, int devnum, struct udevice **devp);
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/**
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* blk_first_device() - Find the first device for a given interface
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*
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* The device is probed ready for use
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*
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* @devnum: Device number (specific to each interface type)
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* @devp: the device, if found
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* @return 0 if found, -ENODEV if no device, or other -ve error value
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*/
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int blk_first_device(int if_type, struct udevice **devp);
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/**
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* blk_next_device() - Find the next device for a given interface
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*
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* This can be called repeatedly after blk_first_device() to iterate through
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* all devices of the given interface type.
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*
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* The device is probed ready for use
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*
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* @devp: On entry, the previous device returned. On exit, the next
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* device, if found
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* @return 0 if found, -ENODEV if no device, or other -ve error value
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*/
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int blk_next_device(struct udevice **devp);
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/**
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* blk_create_device() - Create a new block device
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*
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* @parent: Parent of the new device
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* @drv_name: Driver name to use for the block device
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* @name: Name for the device
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* @if_type: Interface type (enum if_type_t)
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* @devnum: Device number, specific to the interface type
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* @blksz: Block size of the device in bytes (typically 512)
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* @size: Total size of the device in bytes
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* @devp: the new device (which has not been probed)
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*/
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int blk_create_device(struct udevice *parent, const char *drv_name,
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const char *name, int if_type, int devnum, int blksz,
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lbaint_t size, struct udevice **devp);
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/**
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* blk_prepare_device() - Prepare a block device for use
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*
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* This reads partition information from the device if supported.
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*
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* @dev: Device to prepare
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* @return 0 if ok, -ve on error
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*/
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int blk_prepare_device(struct udevice *dev);
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/**
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* blk_unbind_all() - Unbind all device of the given interface type
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*
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* The devices are removed and then unbound.
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*
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* @if_type: Interface type to unbind
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* @return 0 if OK, -ve on error
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*/
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int blk_unbind_all(int if_type);
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#else
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#include <errno.h>
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/*
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* These functions should take struct udevice instead of struct blk_desc,
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* but this is convenient for migration to driver model. Add a 'd' prefix
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* to the function operations, so that blk_read(), etc. can be reserved for
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* functions with the correct arguments.
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*/
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static inline ulong blk_dread(struct blk_desc *block_dev, lbaint_t start,
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lbaint_t blkcnt, void *buffer)
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{
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ulong blks_read;
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if (blkcache_read(block_dev->if_type, block_dev->devnum,
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start, blkcnt, block_dev->blksz, buffer))
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return blkcnt;
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/*
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* We could check if block_read is NULL and return -ENOSYS. But this
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* bloats the code slightly (cause some board to fail to build), and
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* it would be an error to try an operation that does not exist.
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*/
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blks_read = block_dev->block_read(block_dev, start, blkcnt, buffer);
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if (blks_read == blkcnt)
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blkcache_fill(block_dev->if_type, block_dev->devnum,
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start, blkcnt, block_dev->blksz, buffer);
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return blks_read;
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}
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static inline ulong blk_dwrite(struct blk_desc *block_dev, lbaint_t start,
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lbaint_t blkcnt, const void *buffer)
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{
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blkcache_invalidate(block_dev->if_type, block_dev->devnum);
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return block_dev->block_write(block_dev, start, blkcnt, buffer);
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}
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static inline ulong blk_derase(struct blk_desc *block_dev, lbaint_t start,
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lbaint_t blkcnt)
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{
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blkcache_invalidate(block_dev->if_type, block_dev->devnum);
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return block_dev->block_erase(block_dev, start, blkcnt);
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}
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#endif /* !CONFIG_BLK */
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#endif
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