linux2.6.20 sd/mmc卡驱动学习日记3(基于s3c2440)

至此，我们已经跟踪了mmc/sd卡驱动的注册。。我们接着来看插入拔除卡的中断处理函数：

static irqreturn_t s3cmci_irq_cd(int irq, void *dev_id) {     struct s3cmci_host *host = (struct s3cmci_host *)dev_id;     dbg(host, dbg_irq, "card detect/n");     mmc_detect_change(host->mmc, 500);     return IRQ_HANDLED; }

可见，这里也会调用mmc_detect_change。。。我们跟着前面的分析来到mmc_setup这里，此时mmc_setup调用mmc_discover_cards。Create a mmc_card entry for each discovered card，addnew card tolist.同时还会调用mmc_read_switch_caps或者mmc_process_ext_csds来实现对大容量卡的支持(>4G)
跟着程序的流程我们来到
if (!mmc_card_present(card) && !mmc_card_dead(card)) {
            if (mmc_register_card(card))
来看

int mmc_register_card(struct mmc_card *card) {     int ret;     snprintf(card->dev.bus_id, sizeof(card->dev.bus_id),          "%s:%04x", mmc_hostname(card->host), card->rca);     ret = device_add(&card->dev);     if (ret == 0) {         if (mmc_card_sd(card)) {             ret = device_create_file(&card->dev, &mmc_dev_attr_scr);             if (ret)                 device_del(&card->dev); } }     return ret; }

此函数在mmc_sysfs.c中定义。device_add(&card->dev)将到相应总线mmc_bus_type上去搜索相应驱动。找到驱动后就设置dev->driver=drv,并调用mmc_bus_type总线的probe函数被调用，即mmmc_bus_probe函数

static int mmc_bus_probe(struct device *dev) {     struct mmc_driver *drv = to_mmc_driver(dev->driver);     struct mmc_card *card = dev_to_mmc_card(dev);     return drv->probe(card); }

mmc_bus_probe会调用mmc_blk_probe
mmc_blk_probe()首先分配一个新的mmc_blk_data结构变量，然后调用mmc_init_queue，初始化blk队列。然后建立一个线程mmc_queue_thread()。

static int mmc_blk_probe(struct mmc_card *card) {     struct mmc_blk_data *md;     int err;     /*      * Check that the card supports the command class(es) we need.     */     if (!(card->csd.cmdclass & CCC_BLOCK_READ))         return -ENODEV;     md = mmc_blk_alloc(card);//     if (IS_ERR(md))         return PTR_ERR(md);     err = mmc_blk_set_blksize(md, card);     if (err)         goto out;     printk(KERN_INFO "%s: %s %s %lluKiB %s/n",         md->disk->disk_name, mmc_card_id(card), mmc_card_name(card),         (unsigned long long)(get_capacity(md->disk) >> 1),         md->read_only ? "(ro)" : "");     mmc_set_drvdata(card, md);     add_disk(md->disk);     return 0;  out:     mmc_blk_put(md);     return err; }

struct mmc_blk_data封装了struct gendisk  与 struct mmc_queue,而struct mmc_queue封装了struct mmc_card与struct request。

static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card) {     struct mmc_blk_data *md;     int devidx, ret;     devidx = find_first_zero_bit(dev_use, MMC_NUM_MINORS);     if (devidx >= MMC_NUM_MINORS)         return ERR_PTR(-ENOSPC);     __set_bit(devidx, dev_use);     md = kmalloc(sizeof(struct mmc_blk_data), GFP_KERNEL);     if (!md) {         ret = -ENOMEM;         goto out; }     memset(md, 0, sizeof(struct mmc_blk_data));     /*      * Set the read-only status based on the supported commands      * and the write protect switch.     */     md->read_only = mmc_blk_readonly(card);//写保护     /*      * Both SD and MMC specifications state (although a bit      * unclearly in the MMC case) that a block size of 512      * bytes must always be supported by the card.     */     md->block_bits = 9;//块大小     md->disk = alloc_disk(1 << MMC_SHIFT);         //分配struct gendist,驱动程序不能自己动态分配该结构，而是必须调用         //alloc_disk,其参数为次设备号数目，注意了，是次设备号数目，不是次设备号     if (md->disk == NULL) {         ret = -ENOMEM;         goto err_kfree; }     spin_lock_init(&md->lock);     md->usage = 1;     ret = mmc_init_queue(&md->queue, card, &md->lock);//     if (ret)         goto err_putdisk;     md->queue.prep_fn = mmc_blk_prep_rq;     md->queue.issue_fn = mmc_blk_issue_rq;     md->queue.data = md;         //上面设置了请求队列，现在就可以初始化及安装相应的gendisk结构了     md->disk->major    = major;     md->disk->first_minor = devidx << MMC_SHIFT;     md->disk->fops = &mmc_bdops;     md->disk->private_data = md;     md->disk->queue = md->queue.queue;     md->disk->driverfs_dev = &card->dev;     /*      * As discussed on lkml, GENHD_FL_REMOVABLE should:      *      * - be set for removable media with permanent block devices      * - be unset for removable block devices with permanent media      *      * Since MMC block devices clearly fall under the second      * case, we do not set GENHD_FL_REMOVABLE. Userspace      * should use the block device creation/destruction hotplug      * messages to tell when the card is present.     */     sprintf(md->disk->disk_name, "mmcblk%d", devidx);     blk_queue_hardsect_size(md->queue.queue, 1 << md->block_bits);     /*      * The CSD capacity field is in units of read_blkbits.      * set_capacity takes units of 512 bytes.     */     set_capacity(md->disk, card->csd.capacity << (card->csd.read_blkbits - 9));     return md;  err_putdisk:     put_disk(md->disk);  err_kfree:     kfree(md);  out:     return ERR_PTR(ret); }

至此，驱动向系统添加了一个块设备。
请求处理过程：
mmc_request--->mmc_queue_thread----->mmc_blk_issue_rq---->mmc_wait_for_req--->mmc_start_request---->s3cm