USB: g_file_storage: Set sense info Valid bit only when needed

Strictly speaking, the Valid bit in SCSI sense data is supposed to
be set only when the Information field contains a valid number.  This
patch (as793) turns off the Valid bit when the Information field
hasn't been set.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/file_storage.c

@@ -567,6 +567,7 @@ struct lun {
 	unsigned int	ro : 1;
 	unsigned int	prevent_medium_removal : 1;
 	unsigned int	registered : 1;
+	unsigned int	info_valid : 1;
 
 	u32		sense_data;
 	u32		sense_data_info;
@@ -1656,6 +1657,7 @@ static int do_read(struct fsg_dev *fsg)
 			curlun->sense_data =
 					SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
 			curlun->sense_data_info = file_offset >> 9;
+			curlun->info_valid = 1;
 			bh->inreq->length = 0;
 			bh->state = BUF_STATE_FULL;
 			break;
@@ -1691,6 +1693,7 @@ static int do_read(struct fsg_dev *fsg)
 		if (nread < amount) {
 			curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
 			curlun->sense_data_info = file_offset >> 9;
+			curlun->info_valid = 1;
 			break;
 		}
 
@@ -1785,6 +1788,7 @@ static int do_write(struct fsg_dev *fsg)
 				curlun->sense_data =
 					SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
 				curlun->sense_data_info = usb_offset >> 9;
+				curlun->info_valid = 1;
 				continue;
 			}
 			amount -= (amount & 511);
@@ -1827,6 +1831,7 @@ static int do_write(struct fsg_dev *fsg)
 			if (bh->outreq->status != 0) {
 				curlun->sense_data = SS_COMMUNICATION_FAILURE;
 				curlun->sense_data_info = file_offset >> 9;
+				curlun->info_valid = 1;
 				break;
 			}
 
@@ -1868,6 +1873,7 @@ static int do_write(struct fsg_dev *fsg)
 			if (nwritten < amount) {
 				curlun->sense_data = SS_WRITE_ERROR;
 				curlun->sense_data_info = file_offset >> 9;
+				curlun->info_valid = 1;
 				break;
 			}
 
@@ -2010,6 +2016,7 @@ static int do_verify(struct fsg_dev *fsg)
 			curlun->sense_data =
 					SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
 			curlun->sense_data_info = file_offset >> 9;
+			curlun->info_valid = 1;
 			break;
 		}
 
@@ -2036,6 +2043,7 @@ static int do_verify(struct fsg_dev *fsg)
 		if (nread == 0) {
 			curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
 			curlun->sense_data_info = file_offset >> 9;
+			curlun->info_valid = 1;
 			break;
 		}
 		file_offset += nread;
@@ -2079,6 +2087,7 @@ static int do_request_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
 	struct lun	*curlun = fsg->curlun;
 	u8		*buf = (u8 *) bh->buf;
 	u32		sd, sdinfo;
+	int		valid;
 
 	/*
 	 * From the SCSI-2 spec., section 7.9 (Unit attention condition):
@@ -2106,15 +2115,18 @@ static int do_request_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
 		fsg->bad_lun_okay = 1;
 		sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;
 		sdinfo = 0;
+		valid = 0;
 	} else {
 		sd = curlun->sense_data;
 		sdinfo = curlun->sense_data_info;
+		valid = curlun->info_valid << 7;
 		curlun->sense_data = SS_NO_SENSE;
 		curlun->sense_data_info = 0;
+		curlun->info_valid = 0;
 	}
 
 	memset(buf, 0, 18);
-	buf[0] = 0x80 | 0x70;			// Valid, current error
+	buf[0] = valid | 0x70;			// Valid, current error
 	buf[2] = SK(sd);
 	put_be32(&buf[3], sdinfo);		// Sense information
 	buf[7] = 18 - 8;			// Additional sense length
@@ -2703,6 +2715,7 @@ static int check_command(struct fsg_dev *fsg, int cmnd_size,
 		if (fsg->cmnd[0] != SC_REQUEST_SENSE) {
 			curlun->sense_data = SS_NO_SENSE;
 			curlun->sense_data_info = 0;
+			curlun->info_valid = 0;
 		}
 	} else {
 		fsg->curlun = curlun = NULL;
@@ -3332,6 +3345,7 @@ static void handle_exception(struct fsg_dev *fsg)
 			curlun->sense_data = curlun->unit_attention_data =
 					SS_NO_SENSE;
 			curlun->sense_data_info = 0;
+			curlun->info_valid = 0;
 		}
 		fsg->state = FSG_STATE_IDLE;
 	}