Scsi - Index of

222 value, index, size);
223
224 /* fill in the devrequest structure */
225 us->cr->bRequestType = requesttype;
226 us->cr->bRequest = request;
227 us->cr->wValue = cpu_to_le16(value);
228 us->cr->wIndex = cpu_to_le16(index);
229 us->cr->wLength = cpu_to_le16(size);
230
231 /* fill and submit the URB */
232 usb_fill_control_urb(us->current_urb, us->pusb_dev, pipe,
233 (unsigned char*) us->cr, data, size,
234 usb_stor_blocking_completion, NULL);
235 status = usb_stor_msg_common(us, timeout);
236
237 /* return the actual length of the data transferred if no error */
238 if (status == 0)
239 status = us->current_urb->actual_length;
74
240 return status;
241 }
这里相对麻烦一点的函数是usb_stor_msg_common,仍然是我们自己定义的函数,所以我们又得继续
往下一层看,这么多层函数调用的确挺让人看了头晕,一个人总要走陌生的路,看陌生的风景,听陌生的歌,然
后在某个不经意的瞬间,你会发现,原本费尽心机想要弄清楚的函数就这么把自己弄糊涂了.然而,就像世上
的每一条路都是弯的一样,每一个模块都会有曲折的函数调用,写代码的哥们儿为了表现自己一流的编剧水
平,永远不会让我们一路平稳的看完整个模块的.除了面对,我们别无选择,毕竟从我们年幼时,摇篮就告诉我
们,人生是不平静的,也是动荡的,所以为何不微笑着面对这些麻烦?这个函数仍旧是来自
drivers/usb/storage/transport.c:
132 /* This is the common part of the URB message submission code
133 *
134 * All URBs from the usb-storage driver involved in handling a queued scsi
135 * command _must_ pass through this function (or something like it) for the
136 * abort mechanisms to work properly.
137 */
138 static int usb_stor_msg_common(struct us_data *us, int timeout)
139 {
140 struct completion urb_done;
141 struct timer_list to_timer;
142 int status;
143
144 /* don't submit URBs during abort/disconnect processing */
145 if (us->flags & ABORTING_OR_DISCONNECTING)
146 return -EIO;
147