Scsi - Index of

446 if (us->flags & ABORTING_OR_DISCONNECTING)
447 return USB_STOR_XFER_ERROR;
448
449 /* initialize the scatter-gather request block */
450 US_DEBUGP("%s: xfer %u bytes, %d entries\n", __FUNCTION__,
451 length, num_sg);
452 result = usb_sg_init(&us->current_sg, us->pusb_dev, pipe, 0,
453 sg, num_sg, length, SLAB_NOIO);
454 if (result) {
455 US_DEBUGP("usb_sg_init returned %d\n", result);
456 return USB_STOR_XFER_ERROR;
457 }
458
459 /* since the block has been initialized successfully, it's now
460 * okay to cancel it */
461 set_bit(US_FLIDX_SG_ACTIVE, &us->flags);
462
463 /* did an abort/disconnect occur during the submission? */
464 if (us->flags & ABORTING_OR_DISCONNECTING) {
465
466 /* cancel the request, if it hasn't been cancelled already */
467 if (test_and_clear_bit(US_FLIDX_SG_ACTIVE, &us->flags)) {
468 US_DEBUGP("-- cancelling sg request\n");
469 usb_sg_cancel(&us->current_sg);
470 }
471 }
472
163
473 /* wait for the completion of the transfer */
474 usb_sg_wait(&us->current_sg);
475 clear_bit(US_FLIDX_SG_ACTIVE, &us->flags);
476
477 result = us->current_sg.status;
478 if (act_len)
479 *act_len = us->current_sg.bytes;
480 return interpret_urb_result(us, pipe, length, result,
481 us->current_sg.bytes);
482 }
usb_stor_bulk_transfer_sg()函数中,判断use_sg 是否为0,从而确定是否用scatter-gather.对于
use_sg 等于0 的情况,表示不用scatter-gather,那么调用usb_stor_bulk_transfer_buf()发送scsi
命令.实_________际传递的数据长度用partial 记录,然后length_left 就记录还剩下多少没传递,初值当
然就是期望
传递的那个长度.每次减去实际传递的长度即可.对于use_sg 不等于0 的情
况,usb_stor_bulk_transfer_sglist()函数被调用.我们来看这个函数.