ARM的嵌入式Linux移植体验之设备驱动

static int erase_write (struct mtd_info *mtd, unsigned long pos,
int len, const char *buf)
{
　struct erase_info erase;
　DECLARE_WAITQUEUE(wait, current);
　wait_queue_head_t wait_q;
　size_t retlen;
　int ret;

　/*
　* First, let's erase the flash block.
　*/

　init_waitqueue_head(wait_q);
　erase.mtd = mtd;
　erase.callback = erase_callback;
　erase.addr = pos;
　erase.len = len;
　erase.priv = (u_long)wait_q;

　set_current_state(TASK_INTERRUPTIBLE);
　add_wait_queue(wait_q, wait);

　ret = MTD_ERASE(mtd, erase);
　if (ret) {
　　set_current_state(TASK_RUNNING);
　　remove_wait_queue(wait_q, wait);
　　printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " "on /"%s/" failed/n",
pos, len, mtd->name);
　　return ret;
　}

　schedule(); /* Wait for erase to finish. */
　remove_wait_queue(wait_q, wait);

　/*
　* Next, writhe data to flash.
　*/

　ret = MTD_WRITE (mtd, pos, len, retlen, buf);
　if (ret)
　　return ret;
　if (retlen != len)
　　return -EIO;
　return 0;
}

static int write_cached_data (struct mtdblk_dev *mtdblk)
{
　struct mtd_info *mtd = mtdblk->mtd;
　int ret;

　if (mtdblk->cache_state != STATE_DIRTY)
　　return 0;

　DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for /"%s/" "
"at 0x%lx, size 0x%x/n", mtd->name,
mtdblk->cache_offset, mtdblk->cache_size);

　ret = erase_write (mtd, mtdblk->cache_offset,
mtdblk->cache_size, mtdblk->cache_data);
　if (ret)
　　return ret;

　mtdblk->cache_state = STATE_EMPTY;
　return 0;
}

static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
int len, const char *buf)
{
　…
}

static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
int len, char *buf)
{
　…
}

static int mtdblock_open(struct inode *inode, struct file *file)
{
　…
}

static release_t mtdblock_release(struct inode *inode, struct file *file)
{
　int dev;
　struct mtdblk_dev *mtdblk;
　DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release/n");

　if (inode == NULL)
　　release_return(-ENODEV);

　dev = minor(inode->i_rdev);
　mtdblk = mtdblks[dev];

　down(mtdblk->cache_sem);
　write_cached_data(mtdblk);
　up(mtdblk->cache_sem);

　spin_lock(mtdblks_lock);
　if (!--mtdblk->count) {
　　/* It was the last usage. Free the device */
　　mtdblks[dev] = NULL;
　　spin_unlock(mtdblks_lock);
　　if (mtdblk->mtd->sync)
　　　mtdblk->mtd->sync(mtdblk->mtd);
　　　put_mtd_device(mtdblk->mtd);
　　　vfree(mtdblk->cache_data);
　　　kfree(mtdblk);
　} else {
　　spin_unlock(mtdblks_lock);
　}

　DEBUG(MTD_DEBUG_LEVEL1, "ok/n");
　
　BLK_DEC_USE_COUNT;
　release_return(0);
}

/*
* This is a special request_fn because it is executed in a process context
* to be able to sleep independently of the caller. The
* io_request_lock (for 2.5) or queue_lock (for >=2.5) is held upon entry
* and exit. The head of our request queue is considered active so there is
* no need to dequeue requests before we are done.
*/
static void handle_mtdblock_request(void)
{
　struct request *req;
　struct mtdblk_dev *mtdblk;
　unsigned int res;

　for (;;) {
　　INIT_REQUEST;
　　req = CURRENT;
　　spin_unlock_irq(QUEUE_LOCK(QUEUE));
　　mtdblk = mtdblks[minor(req->rq_dev)];
　　res = 0;

　　if (minor(req->rq_dev) >= MAX_MTD_DEVICES)
　　　panic("%s : minor out of bound", __FUNCTION__);

　　if (!IS_REQ_CMD(req))
　　　goto end_req;

　　if ((req->sector + req->current_nr_sectors) > (mtdblk->mtd->size >> 9))
　　　goto end_req;

　　// Handle the request
　　switch (rq_data_dir(req))
　　{
　　　int err;

　　　case READ:
　　　　down(mtdblk->cache_sem);
　　　　err = do_cached_read (mtdblk, req->sector 9,
req->current_nr_sectors 9,
req->buffer);
　　　　up(mtdblk->cache_sem);
　　　　if (!err)
　　　　　res = 1;
　　　　break;