ARM的嵌入式Linux移植體驗之設備驅動

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;

　　　case WRITE:
　　　　// Read only device
　　　　if ( !(mtdblk->mtd->flags MTD_WRITEABLE) )
　　　　　break;

　　　　// Do the write
　　　　down(mtdblk->cache_sem);
　　　　err = do_cached_write (mtdblk, req->sector 9,req->current_nr_sectors 9, req->buffer);
　　　　up(mtdblk->cache_sem);
　　　　if (!err)
　　　　　res = 1;
　　　　break;
　　}

　end_req:
　spin_lock_irq(QUEUE_LOCK(QUEUE));
　end_request(res);
}
}

static volatile int leaving = 0;
static DECLARE_MUTEX_LOCKED(thread_sem);
static DECLARE_WAIT_QUEUE_HEAD(thr_wq);

int mtdblock_thread(void *dummy)
{
　…
}

#define RQFUNC_ARG request_queue_t *q

static void mtdblock_request(RQFUNC_ARG)
{
　/* Don't do anything, except wake the thread if necESSary */
　wake_up(thr_wq);
}

static int mtdblock_ioctl(struct inode * inode, struct file * file,
unsigned int CMd, unsigned long arg)
{
　struct mtdblk_dev *mtdblk;
　mtdblk = mtdblks[minor(inode->i_rdev)];
　switch (cMD) {
　　case BLKGETSIZE: /* Return device size */
　　　return put_user((mtdblk->mtd->size >> 9), (unsigned long *) arg);

　　case BLKFLSBUF:
　　　if(!capable(CAP_SYS_ADMIN))
　　　　return -EACCES;
　　　fsync_dev(inode->i_rdev);
　　　invalidate_buffers(inode->i_rdev);
　　　down(mtdblk->cache_sem);
　　　write_cached_data(mtdblk);
　　　up(mtdblk->cache_sem);
　　　if (mtdblk->mtd->sync)
　　　　mtdblk->mtd->sync(mtdblk->mtd);
　　　　return 0;
　　default:
　　　return -EINVAL;
　}
}