/**
* @file rtems/bdbuf.h
*
* block device buffer management
*/
/*
* Copyright (C) 2001 OKTET Ltd., St.-Petersburg, Russia
* Author: Victor V. Vengerov <vvv@oktet.ru>
*
* @(#) $Id$
*/
#ifndef _RTEMS_BDBUF_H
#define _RTEMS_BDBUF_H
#ifdef __cplusplus
extern "C" {
#endif
#include <rtems.h>
#include <rtems/libio.h>
#include <rtems/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 */
unsigned 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 */
unsigned 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
