2、mmc_start_host & mmc_stop_host

mmc_start_host 用来启动一个host，mmc_stop_host用来停止一个host。 
当底层host controller调用mmc_add_host来注册host时，在mmc_add_host中就会调用mmc_start_host来

启动一个host了。具体参考《mmc core——host模块说明》。 
相对应的，会在mmc_remove_host中调用mmc_stop_host停止host。

voidmmc_start_host(structmmc_host *host)

{

mmc_claim_host(host);// 因为上电操作涉及到对host的使用和设置，需要先占用

host host->f_init =max(freqs[0], host->f_min); // 通过最小频率要设置初始化频率

host->rescan_disable = 0; // 设置rescan_disable标志为0，说明已经可以进行card检测了

if(host->caps2 & MMC_CAP2_NO_PRESCAN_POWERUP) 

// 如果mmc属性设置了MMC_CAP2_NO_PRESCAN_POWERUP，也就是在rescan前不需要进行

power up操作时，则进行关电

mmc_power_off(host);

elsemmc_power_up(host); // 否则，调用mmc_power_up对host进行上电操作。

这里也是mmc core中启动host的核心函数。

3.

 static struct mmc_host_ops mt_msdc_ops= {

   .post_req        = msdc_post_req,

   .pre_req         = msdc_pre_req,

    .request        = msdc_ops_request,

   .tuning          =msdc_tune_async_request,

   .set_ios         =msdc_ops_set_ios,

   .get_ro          =msdc_ops_get_ro,

   .get_cd          =msdc_ops_get_cd,

   .enable_sdio_irq = msdc_ops_enable_sdio_irq,

   .start_signal_voltage_switch = msdc_ops_switch_volt,

   .send_stop       = msdc_ops_stop,

   .dma_error_reset = msdc_dma_error_reset,

   .check_written_data = msdc_check_written_data,

};

static void

mmc_start_request(struct mmc_host*host, struct mmc_request *mrq)

{

#ifdef CONFIG_MMC_DEBUG

       unsignedint i, sz;

       structscatterlist *sg;

#endif

staticint __mmc_start_req(struct mmc_host *host, struct mmc_request *mrq)

{

         init_completion(&mrq->completion);

         mrq->done = mmc_wait_done;

         if (mmc_card_removed(host->card)) {

                   mrq->cmd->error =-ENOMEDIUM;

                   complete(&mrq->completion);

                   return -ENOMEDIUM;

         }

         mmc_start_request(host, mrq);  ------- host->ops->request(host, mrq);

         return 0;

}

4. 函数完成块设备驱动的模块加载模板

static structmmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,

                         struct device *parent,

                         sector_t size,

                          booldefault_ro,

                          constchar *subname,

                          intarea_type)

{

    md->queue.issue_fn = mmc_blk_issue_rq;

    md->queue.data = md;

 

    md->disk->major =MMC_BLOCK_MAJOR;

    md->disk->first_minor = devidx * perdev_minors;

    md->disk->fops =&mmc_bdops;