Scsi - Index of

920 US_DEBUGP("GetMaxLUN command result is %d, data is %d\n",
921 result, us->iobuf[0]);
922
923 /* if we have a successful request, return the result */
924 if (result > 0)
925 return us->iobuf[0];
926
927 /*
928 * Some devices (i.e. Iomega Zip100) need this -- apparently
929 * the bulk pipes get STALLed when the GetMaxLUN request is
930 * processed. This is, in theory, harmless to all other devices
931 * (regardless of if they stall or not).
932 */
933 if (result == -EPIPE) {
934 usb_stor_clear_halt(us, us->recv_bulk_pipe);
935 usb_stor_clear_halt(us, us->send_bulk_pipe);
936 }
937
938 /*
73
939 * Some devices don't like GetMaxLUN. They may STALL the control
940 * pipe, they may return a zero-length result, they may do nothing at
941 * all and timeout, or they may fail in even more bizarrely creative
942 * ways. In these cases the best approach is to use the default
943 * value: only one LUN.
944 */
945 return 0;
946 }
代码不长,不过并不容易.首先914 行, usb_stor_control_msg()函数被调用,这也是我们自己定义的函
数,所以也得讲,同样来自drivers/usb/storage/transport.c:
209
210 /*
211 * Transfer one control message, with timeouts, and allowing early
212 * termination. Return codes are usual -Exxx, *not* USB_STOR_XFER_xxx.
213 */
214 int usb_stor_control_msg(struct us_data *us, unsigned int pipe,
215 u8 request, u8 requesttype, u16 value, u16 index,
216 void *data, u16 size, int timeout)
217 {
218 int status;
219
220 US_DEBUGP("%s: rq=%02x rqtype=%02x value=%04x index=%02x
len=%u\n",
221 __FUNCTION__, request, requesttype,