Subversion Repositories or1k

/* bdbuf.h -- block device buffer management

 *

 * Copyright (C) 2001 OKTET Ltd., St.-Petersburg, Russia

 * Author: Victor V. Vengerov <vvv@oktet.ru>

 *

 * @(#) bdbuf.h,v 1.3 2002/04/03 13:56:34 joel Exp

 */

#ifndef __RTEMS_LIBBLOCK_BDBUF_H__

#define __RTEMS_LIBBLOCK_BDBUF_H__

#ifdef __cplusplus

extern "C" {

#endif

#include <rtems.h>

#include <rtems/libio.h>

#include <chain.h>

#include "rtems/blkdev.h"

#include "rtems/diskdevs.h"

/*

 * To manage buffers we using Buffer Descriptors.

 * To speed-up buffer lookup descriptors are organized in AVL-Tree.

 * The fields 'dev' and 'block' are search key.

 */

/* Buffer descriptors

 * Descriptors organized in AVL-tree to speedup buffer lookup.

 * dev and block fields are search key in AVL-tree.

 * Modified buffers, free buffers and used buffers linked in 'mod', 'free' and

 * 'lru' chains appropriately.

 */

typedef struct bdbuf_buffer {

    Chain_Node link; /* Link in the lru, mod or free chains */

    struct bdbuf_avl_node {

        signed char cache;           /* Cache */

            struct bdbuf_buffer* left;  /* Left Child */

            struct bdbuf_buffer* right; /* Right Child */

        signed char bal;             /* The balance of the sub-tree */

    } avl;

    dev_t       dev;     /* device number */

    blkdev_bnum block;   /* block number on the device */

    char       *buffer;  /* Pointer to the buffer memory area */

    rtems_status_code status; /* Last I/O operation completion status */

    int         error;   /* If status != RTEMS_SUCCESSFUL, this field contains

                            errno value which can be used by user later */

    boolean     modified:1;    /* =1 if buffer was modified */

    boolean     in_progress:1; /* =1 if exchange with disk is in progress;

                                  need to wait on semaphore */

    boolean     actual:1;      /* Buffer contains actual data */

    int         use_count; /* Usage counter; incremented when somebody use

                              this buffer; decremented when buffer released

                              without modification or when buffer is flushed

                              by swapout task */

    rtems_bdpool_id pool;  /* Identifier of buffer pool to which this buffer

                              belongs */

    CORE_mutex_Control transfer_sema;

                           /* Transfer operation semaphore */

} bdbuf_buffer;

/* bdbuf_config structure describes block configuration (size,

 * amount, memory location) for buffering layer

 */

typedef struct rtems_bdbuf_config {

    int     size;     /* Size of block */

    int     num;      /* Number of blocks of appropriate size */

    char   *mem_area; /* Pointer to the blocks location or NULL, in this

                          case memory for blocks will be allocated by

                          Buffering Layer with the help of RTEMS partition

                          manager */

} rtems_bdbuf_config;

extern rtems_bdbuf_config rtems_bdbuf_configuration[];

extern int rtems_bdbuf_configuration_size;

/* rtems_bdbuf_init --

 *     Prepare buffering layer to work - initialize buffer descritors

 *     and (if it is neccessary) buffers. Buffers will be allocated accoriding

 *     to the configuration table, each entry describes kind of block and

 *     amount requested. After initialization all blocks is placed into

 *     free elements lists.

 *

 * PARAMETERS:

 *     conf_table - pointer to the buffers configuration table

 *     size       - number of entries in configuration table

 *

 * RETURNS:

 *     RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully

 *     or error code if error is occured)

 */

rtems_status_code

rtems_bdbuf_init(rtems_bdbuf_config *conf_table, int size);

/* rtems_bdbuf_get --

 *     Obtain block buffer. If specified block already cached (i.e. there's

 *     block in the _modified_, or _recently_used_), return address

 *     of appropriate buffer descriptor and increment reference counter to 1.

 *     If block is not cached, allocate new buffer and return it. Data

 *     shouldn't be read to the buffer from media; buffer may contains

 *     arbitrary data. This primitive may be blocked if there are no free

 *     buffer descriptors available and there are no unused non-modified

 *     (or synchronized with media) buffers available.

 *

 * PARAMETERS:

 *     device - device number (constructed of major and minor device number)

 *     block  - linear media block number

 *     bd     - address of variable to store pointer to the buffer descriptor

 *

 * RETURNS:

 *     RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully

 *     or error code if error is occured)

 *

 * SIDE EFFECTS:

 *     bufget_sema semaphore obtained by this primitive.

 */

rtems_status_code

rtems_bdbuf_get(dev_t device, blkdev_bnum block, bdbuf_buffer **bdb_ptr);

/* rtems_bdbuf_read --

 *     (Similar to the rtems_bdbuf_get, except reading data from media)

 *     Obtain block buffer. If specified block already cached, return address

 *     of appropriate buffer and increment reference counter to 1. If block is

 *     not cached, allocate new buffer and read data to it from the media.

 *     This primitive may be blocked on waiting until data to be read from

 *     media, if there are no free buffer descriptors available and there are

 *     no unused non-modified (or synchronized with media) buffers available.

 *

 * PARAMETERS:

 *     device - device number (consists of major and minor device number)

 *     block  - linear media block number

 *     bd     - address of variable to store pointer to the buffer descriptor

 *

 * RETURNS:

 *     RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully

 *     or error code if error is occured)

 *

 * SIDE EFFECTS:

 *     bufget_sema and transfer_sema semaphores obtained by this primitive.

 */

rtems_status_code

rtems_bdbuf_read(dev_t device, blkdev_bnum block, bdbuf_buffer **bdb_ptr);

/* rtems_bdbuf_release --

 *     Release buffer allocated before. This primitive decrease the

 *     usage counter. If it is zero, further destiny of buffer depends on

 *     'modified' status. If buffer was modified, it is placed to the end of

 *     mod list and flush task waken up. If buffer was not modified,

 *     it is placed to the end of lru list, and bufget_sema released, allowing

 *     to reuse this buffer.

 *

 * PARAMETERS:

 *     bd_buf - pointer to the bdbuf_buffer structure previously obtained using

 *              get/read primitive.

 *

 * RETURNS:

 *     RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully

 *     or error code if error is occured)

 *

 * SIDE EFFECTS:

 *     flush_sema and bufget_sema semaphores may be released by this primitive.

 */

rtems_status_code

rtems_bdbuf_release(bdbuf_buffer *bd_buf);

/* rtems_bdbuf_release_modified --

 *     Release buffer allocated before, assuming that it is _modified_ by

 *     it's owner. This primitive decrease usage counter for buffer, mark

 *     buffer descriptor as modified. If usage counter is 0, insert it at

 *     end of mod chain and release flush_sema semaphore to activate the

 *     flush task.

 *

 * PARAMETERS:

 *     bd_buf - pointer to the bdbuf_buffer structure previously obtained using

 *              get/read primitive.

 *

 * RETURNS:

 *     RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully

 *     or error code if error is occured)

 *

 * SIDE EFFECTS:

 *     flush_sema semaphore may be released by this primitive.

 */

rtems_status_code

rtems_bdbuf_release_modified(bdbuf_buffer *bd_buf);

/* rtems_bdbuf_sync --

 *     Wait until specified buffer synchronized with disk. Invoked on exchanges

 *     critical for data consistency on the media. This primitive mark owned

 *     block as modified, decrease usage counter. If usage counter is 0,

 *     block inserted to the mod chain and flush_sema semaphore released.

 *     Finally, primitives blocked on transfer_sema semaphore.

 *

 * PARAMETERS:

 *     bd_buf - pointer to the bdbuf_buffer structure previously obtained using

 *              get/read primitive.

 *

 * RETURNS:

 *     RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully

 *     or error code if error is occured)

 *

 * SIDE EFFECTS:

 *     Primitive may be blocked on transfer_sema semaphore.

 */

rtems_status_code

rtems_bdbuf_sync(bdbuf_buffer *bd_buf);

/* rtems_bdbuf_syncdev --

 *     Synchronize with disk all buffers containing the blocks belonging to

 *     specified device.

 *

 * PARAMETERS:

 *     dev - block device number

 *

 * RETURNS:

 *     RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully

 *     or error code if error is occured)

 */

rtems_status_code

rtems_bdbuf_syncdev(dev_t dev);

/* rtems_bdbuf_find_pool --

 *     Find first appropriate buffer pool. This primitive returns the index

 *     of first buffer pool which block size is greater than or equal to

 *     specified size.

 *

 * PARAMETERS:

 *     block_size - requested block size

 *     pool       - placeholder for result

 *

 * RETURNS:

 *     RTEMS status code: RTEMS_SUCCESSFUL if operation completed successfully,

 *     RTEMS_INVALID_SIZE if specified block size is invalid (not a power

 *     of 2), RTEMS_NOT_DEFINED if buffer pool for this or greater block size

 *     is not configured.

 */

rtems_status_code

rtems_bdbuf_find_pool(int block_size, rtems_bdpool_id *pool);

/* rtems_bdbuf_get_pool_info --

 *     Obtain characteristics of buffer pool with specified number.

 *

 * PARAMETERS:

 *     pool       - buffer pool number

 *     block_size - block size for which buffer pool is configured returned

 *                  there

 *     blocks     - number of buffers in buffer pool returned there

 *

 * RETURNS:

 *     RTEMS status code: RTEMS_SUCCESSFUL if operation completed successfully,

 *     RTEMS_INVALID_NUMBER if appropriate buffer pool is not configured.

 *

 * NOTE:

 *     Buffer pools enumerated contiguously starting from 0.

 */

rtems_status_code

rtems_bdbuf_get_pool_info(rtems_bdpool_id pool, int *block_size, int *blocks);

#ifdef __cplusplus

}

#endif

#endif