20150310 块设备驱动程序

struct gendisk {

/*

*这三个成员的定义依次是：主设备号、第一个次设备号，次设备号。一个驱动中至有一个次设备号，

*如果驱动器是一个可被分区，那么每一个分区都将分配一个次设号。

*/

int major;

int first_minor;

int minors;

//这个数组用以存储驱动设备的名字

char disk_name[DISK_NAME_LEN];

char *(*devnode)(struct gendisk *gd, umode_t *mode);

unsigned int events;

unsigned int async_events;

struct disk_part_tbl __rcu *part_tbl;

struct hd_struct part0;

//这个结构体用以设置驱动中的各种设备操作

const struct block_device_operations *fops;

//Linux 内核使用这个结构体为设备管理I/O 请求，具体详解见request_queue 结构。

struct request_queue *queue;

void *private_data;

int flags;

struct device *driverfs_dev;

struct kobject *slave_dir;

struct timer_rand_state *random;

atomic_t sync_io;

struct disk_events *ev;

#ifdef CONFIG_BLK_DEV_INTEGRITY

struct blk_integrity *integrity;

#endif

int node_id;

};

struct bio {

//需要传输的第一个(512byte)扇区

sector_t bi_sector;

struct bio *bi_next;

struct block_device *bi_bdev;

unsigned long bi_flags;

unsigned long bi_rw;

unsigned short bi_vcnt;

unsigned short bi_idx;

//BIO 中所包含的物理段数目

unsigned int bi_phys_segments;

//所传输的数据大小(以byte 为单位)

unsigned int bi_size;

unsigned int bi_seg_front_size;

unsigned int bi_seg_back_size;

unsigned int bi_max_vecs;

atomic_t bi_cnt;

struct bio_vec *bi_io_vec;

bio_end_io_t *bi_end_io;

void *bi_private;

#ifdef CONFIG_BLK_CGROUP

struct io_context *bi_ioc;

struct cgroup_subsys_state *bi_css;

#endif

#if defined(CONFIG_BLK_DEV_INTEGRITY)

struct bio_integrity_payload *bi_integrity;

#endif

bio_destructor_t *bi_destructor;

struct bio_vec bi_inline_vecs[0];

};

struct bio_vec {

struct page *bv_page; /*数据段所在的页*/

unsigned short bv_len; /*数据段的长度*/

unsigned short bv_offset; /*数据段页内偏移*/

};

struct request {

struct list_head queuelist;

struct call_single_data csd;

struct request_queue *q;

unsigned int cmd_flags;

enum rq_cmd_type_bits cmd_type;

unsigned long atomic_flags;

int cpu;

unsigned int __data_len;

sector_t __sector;

struct bio *bio;

struct bio *biotail;

struct hlist_node hash;

union {

struct rb_node rb_node;

void *completion_data;

};

union {

struct {

struct io_cq *icq;

void *priv[2];

} elv;

struct {

unsigned int seq;

struct list_head list;

rq_end_io_fn *saved_end_io;

} flush;

};

struct gendisk *rq_disk;

struct hd_struct *part;

unsigned long start_time;

#ifdef CONFIG_BLK_CGROUP

struct request_list *rl;

unsigned long long start_time_ns;

unsigned long long io_start_time_ns;

#endif

unsigned short nr_phys_segments;

#if defined(CONFIG_BLK_DEV_INTEGRITY)

unsigned short nr_integrity_segments;

#endif

unsigned short ioprio;

int ref_count;

void *special;

char *buffer;

int tag;

int errors;

unsigned char __cmd[BLK_MAX_CDB];

unsigned char *cmd;

unsigned short cmd_len;

unsigned int extra_len;

unsigned int sense_len;

unsigned int resid_len;

void *sense;

unsigned long deadline;

struct list_head timeout_list;

unsigned int timeout;

int retries;

rq_end_io_fn *end_io;

void *end_io_data;

struct request *next_rq;

};

struct request_queue{

    /*

     * Together with queue_head for cacheline sharing

     */

    struct list_head    queue_head;

    struct request        *last_merge;

    struct elevator_queue    *elevator;

    /*

     * the queue request freelist, one for reads and one for writes

     */

    struct request_list    rq;

    request_fn_proc        *request_fn;

    make_request_fn        *make_request_fn;

    prep_rq_fn        *prep_rq_fn;

    unplug_fn        *unplug_fn;

    prepare_discard_fn    *prepare_discard_fn;

    merge_bvec_fn        *merge_bvec_fn;

    prepare_flush_fn    *prepare_flush_fn;

    softirq_done_fn        *softirq_done_fn;

    rq_timed_out_fn        *rq_timed_out_fn;

    dma_drain_needed_fn    *dma_drain_needed;

    lld_busy_fn        *lld_busy_fn;

    /*

     * Dispatch queue sorting

     */

    sector_t        end_sector;

    struct request        *boundary_rq;

    /*

     * Auto-unplugging state

     */

    struct timer_list    unplug_timer;

    int            unplug_thresh;    /* After this many requests */

    unsigned long        unplug_delay;    /* After this many jiffies */

    struct work_struct    unplug_work;

    struct backing_dev_info    backing_dev_info;

    /*

     * The queue owner gets to use this for whatever they like.

     * ll_rw_blk doesn't touch it.

     */

    void            *queuedata;

    /*

     * queue needs bounce pages for pages above this limit

     */

    gfp_t            bounce_gfp;

    /*

     * various queue flags, see QUEUE_* below

     */

    unsigned long        queue_flags;

    /*

     * protects queue structures from reentrancy. ->__queue_lock should

     * _never_ be used directly, it is queue private. always use

     * ->queue_lock.

     */

    spinlock_t        __queue_lock;

    spinlock_t        *queue_lock;

    /*

     * queue kobject

     */

    struct kobject kobj;

    /*

     * queue settings

     */

    unsigned long        nr_requests;    /* Max # of requests */

    unsigned int        nr_congestion_on;

    unsigned int        nr_congestion_off;

    unsigned int        nr_batching;

    void            *dma_drain_buffer;

    unsigned int        dma_drain_size;

    unsigned int        dma_pad_mask;

    unsigned int        dma_alignment;

    struct blk_queue_tag    *queue_tags;

    struct list_head    tag_busy_list;

    unsigned int        nr_sorted;

    unsigned int        in_flight[2];

    unsigned int        rq_timeout;

    struct timer_list    timeout;

    struct list_head    timeout_list;

    struct queue_limits    limits;

    /*

     * sg stuff

     */

    unsigned int        sg_timeout;

    unsigned int        sg_reserved_size;

    int            node;

#ifdef CONFIG_BLK_DEV_IO_TRACE

    struct blk_trace    *blk_trace;

#endif

    /*

     * reserved for flush operations

     */

    unsigned int        ordered, next_ordered, ordseq;

    int            orderr, ordcolor;

    struct request        pre_flush_rq, bar_rq, post_flush_rq;

    struct request        *orig_bar_rq;

    struct mutex        sysfs_lock;

#if defined(CONFIG_BLK_DEV_BSG)

    struct bsg_class_device bsg_dev;

#endif

};

Insmod blk.ko

ll /dev/blkdev

mkfs.ext3 /dev/blkdev

fdisk /dev/blkdev