nandflash学习经历

来源：互联网发布：锵锵三人行德国公知编辑：程序博客网时间：2024/06/06 14:14

经过一段时间的奋斗，终于对nandflash的框架有点了解！

首先nandflash的框架：

                  APP： open read write

----------------------------------------------------------------------

vfs: sys_open sys_read    sys_write

------------------------------------------------------------------

字符设备                       |FS: VFAT EXT2   YAFFS2

                                   | --------------------------------------

                                   | 块设备（优化）

-----------------------------------------------------------------------------

              nandflash协议层（知道读写、扫描nandflsh...)

--------------------------------------------------------------------------------

                   nandflash硬件层 (实现nandchip 结构

                                        |

                                        |__(1) 分配nandchip结构

                                             (2)设置nandchip

                                             (3) 硬件相关设置

                                             (4)使用nandchip结构   nand_scan   add_parition....

首先从/drivers/mtd/nand/AT91_nand.c开始分析

at91_nand_probe
//获得nandflash 的类型
//drivers/mtd/nand/Nand_base.c
nand_scan
  //获得真正nandflash   的类型
  nand_scan_ident
   nand_get_flash_type


  //初始化nandflash使用的函数
  nand_scan_tail
   mtd->read = nand_read;
   mtd->write = nand_write;


//添加分区信息
//drivers/mtd/nand/Mtdpart.c
add_mtd_partitions
  //drivers/mtd/Mtdcore.c
  add_mtd_device
   list_for_each(this, &mtd_notifiers) {//mtd_notifiers在哪初始化此链表？
            // 在register_mtd_user   中添加链表,那此函数哪个中被调用呢？
            //被drivers\mtd\Mtdchar.c 和 drivers\mtd\Mtd_blkdevs.c 调用
   struct mtd_notifier *not = list_entry(this, struct mtd_notifier, list);
   not->add(mtd);
   }

   //drivers\mtd\Mtdchar.c
   //初始化时调用register_mtd_user 函数对 mtd_notifiers进行注册
   init_mtdchar
    register_mtd_user(&notifier);
     //注册链表的时候，上面的not->add(mtd); 实际上就是调用下面结构mtd_notify_add的函数
     //static struct mtd_notifier notifier = {
     //.add = mtd_notify_add,
     //.remove = mtd_notify_remove,
     //};

   mtd_notify_add
    //创建两个设备节点 mtd*   mtd*ro
    class_device_create
    class_device_create



   //drivers\mtd\Mtd_blkdevs.c
   //调用 register_mtd_blktrans对mtd_notifiers进行注册
   register_mtd_blktrans
    register_mtd_user(&blktrans_notifier);
    //注册链表的时候, 上面的not->add(mtd)；实际就是调用blktrans_notify_add此函数
    // static struct mtd_notifier blktrans_notifier = {
    // .add = blktrans_notify_add,
    // .remove = blktrans_notify_remove,
    // };
   //添加函数中又出现个链表blktrans_majors
   blktrans_notify_add
    //list_for_each(this, &blktrans_majors) {//这个链表blktrans_majors又是被谁初始化和添加呢？
         //(1)初始化还是被register_mtd_blktrans
         //  list_add(&tr->list, &blktrans_majors);

    // struct mtd_blktrans_ops *tr = list_entry(this, struct mtd_blktrans_ops, list);
    // tr->add_mtd(tr, mtd);
    //}

   register_mtd_blktrans   被谁调用呢？
   //drivers\mtd\Mtdblock.c   和 drivers\mtd\Mtdblock_ro.c
   //这两个文件初始化的时候，调用register_mtd_blktrans此函数对链表进行初始化
   init_mtdblock(void)
     register_mtd_blktrans(&mtdblock_tr);
     //但是上面链表的.add调用谁呢？
     //答：会调用mtdblock_tr 结构中mtdblock_add_mtd    drivers\mtd\Mtdblock.c
     static struct mtd_blktrans_ops mtdblock_tr = {
     .name  = "mtdblock",
     .major  = 31,
     .part_bits = 0,
     .blksize = 512,
     .open  = mtdblock_open,
     .flush  = mtdblock_flush,
     .release = mtdblock_release,
     .readsect = mtdblock_readsect,
     .writesect = mtdblock_writesect,
     .add_mtd = mtdblock_add_mtd,
     .remove_dev = mtdblock_remove_dev,
     .owner  = THIS_MODULE,
    };

    //上面的.add_mtd会调用此函数
    mtdblock_add_mtd
     //那这个函数中会做写什么呢？
     //drivers/mtd/Mtd_blkdev.c
     add_mtd_blktrans_dev
     //分配一个struct gendisk 结构，又回到用内存模仿nandflsh那一套
     alloc_disk
     //设置容量
     set_capacity
     //初始化一个默认的队列
     gd->queue = tr->blkcore_priv->rq;//blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
     add_disk(gd);


     //那队列mtd_blktrans_request 唤醒函数做些什么呢？
       //唤醒队列,那运行等待队列在哪实现的呢？
       wake_up_process(tr->blkcore_priv->thread);

       register_mtd_blktrans
        //在register_mtd_blktrans注册函数中，有个线程mtd_blktrans_thread
        tr->blkcore_priv->thread = kthread_run(mtd_blktrans_thread,
        tr,"%sd", tr->name);

        mtd_blktrans_thread
         //电梯调度算法
         req = elv_next_request(rq);
         //唤醒后执行do_blktrans_request，没有一直在这休眠
         do_blktrans_request
          //最终还是调用读、写块函数

           struct mtd_blktrans_ops *tr
           tr->readsect(dev, block, buf)
           //实际上就是调用
           .readsect = mtdblock_readsect,

           //而mtdblock_readsect 实际上内部就是调用
           //mtd->read(mtd, pos, size, &retlen, buf);