Martin and Matthew: Since you guys added scsi_vpd_inquiry() and scsi_get_vpd_page() plus sd_read_block_limits() and sd_read_block_characteristics(), I'm directing these questions to you. Is there some reason for not accounting for the 4 header bytes in the allocation length value stored in the CDB? Or is this simply a bug? Were you aware that SCSI-2 defines the allocation length to be a single byte? cmd[3] is specified as "Reserved" in the spec. Hence the value of "len" should be capped at 255 if sdev->scsi_level <= SCSI_2, right? Why does scsi_get_vpd_page() retrieve page 0 first, rather than directly asking for the page in question? Is this some sort of play-it-safe approach, to avoid sending devices commands they may not support? Have you considered that plenty of low-budget USB mass-storage devices don't implement VPD properly? I've got a flash drive right here which totally ignores the "page" byte in the INQUIRY command; it always responds with the normal INQUIRY data. Thus expecting the response data always to be accurate may not be a good idea. I'm considering adding a "restrict_to_MS_usb" flag to the host template, to indicate that commands shouldn't be sent unless some version of Windows uses them when talking to USB devices -- do you think that could work? Finally, what's your opinion on the proposed patch below? Alan Stern Index: usb-2.6/drivers/scsi/scsi.c =================================================================== --- usb-2.6.orig/drivers/scsi/scsi.c +++ usb-2.6/drivers/scsi/scsi.c @@ -969,7 +969,7 @@ EXPORT_SYMBOL(scsi_track_queue_full); * @sdev: The device to ask * @buffer: Where to put the result * @page: Which Vital Product Data to return - * @len: The length of the buffer + * @len: The length of the data (= buffer length - 4) * * This is an internal helper function. You probably want to use * scsi_get_vpd_page instead. @@ -982,6 +982,12 @@ static int scsi_vpd_inquiry(struct scsi_ int result; unsigned char cmd[16]; + len += 4; /* Include room for the header bytes */ + + /* SCSI-2 and earlier allow only 1 byte for the allocation length */ + if (sdev->scsi_level <= SCSI_2) + len = min(len, 255u); + cmd[0] = INQUIRY; cmd[1] = 1; /* EVPD */ cmd[2] = page; @@ -994,7 +1000,7 @@ static int scsi_vpd_inquiry(struct scsi_ * all the existing users tried this hard. */ result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, - len + 4, NULL, 30 * HZ, 3, NULL); + len, NULL, 30 * HZ, 3, NULL); if (result) return result; -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
