Scsi - Index of

491 * scatter-gather or not, and acts appropriately.
492 */
493 int usb_stor_bulk_transfer_sg(struct us_data* us, unsigned int pipe,
494 void *buf, unsigned int length_left, int use_sg, int *residual)
495 {
496 int result;
497 unsigned int partial;
498
499 /* are we scatter-gathering? */
500 if (use_sg) {
501 /* use the usb core scatter-gather primitives */
502 result = usb_stor_bulk_transfer_sglist(us, pipe,
503 (struct scatterlist *) buf, use_sg,
504 length_left, &partial);
505 length_left -= partial;
506 } else {
507 /* no scatter-gather, just make the request */
508 result = usb_stor_bulk_transfer_buf(us, pipe, buf,
509 length_left, &partial);
510 length_left -= partial;
511 }
512
513 /* store the residual and return the error code */
514 if (residual)
515 *residual = length_left;
516 return result;
517 }
162
注释说得很清楚,这个函数是一个壳,真正干活的是她所调用或者说利用的那两个函
数.usb_stor_bulk_transfer_sglist()和usb_stor_bulk_transfer_buf().后者咱们刚才已经遇到过了,
而前者是专门为scatter-gather 传输准备的函数,她也来自drivers/usb/storage/transport.c 中:
433 /*
434 * Transfer a scatter-gather list via bulk transfer
435 *
436 * This function does basically the same thing as usb_stor_bulk_transfer_buf()
437 * above, but it uses the usbcore scatter-gather library.
438 */
439 int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe,
440 struct scatterlist *sg, int num_sg, unsigned int length,
441 unsigned int *act_len)
442 {
443 int result;
444
445 /* don't submit s-g requests during abort/disconnect processing */