scsi: core: Fixup calling convention for scsi_mode_sense()

The description for scsi_mode_sense() claims to return the number of valid
bytes on success, which is not what the code does.  Additionally there is
no gain in returning the SCSI status, as everything the callers do is to
check against scsi_result_is_good(), which is what scsi_mode_sense() does
already.  So change the calling convention to return a standard error code
on failure, and 0 on success, and adapt the description and all callers.

Link: https://lore.kernel.org/r/20210427083046.31620-4-hare@suse.de
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -2093,9 +2093,7 @@ EXPORT_SYMBOL_GPL(scsi_mode_select);
  *	@sshdr: place to put sense data (or NULL if no sense to be collected).
  *		must be SCSI_SENSE_BUFFERSIZE big.
  *
- *	Returns zero if unsuccessful, or the header offset (either 4
- *	or 8 depending on whether a six or ten byte command was
- *	issued) if successful.
+ *	Returns zero if successful, or a negative error number on failure
  */
 int
 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
@@ -2142,6 +2140,8 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 
 	result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
 				  sshdr, timeout, retries, NULL);
+	if (result < 0)
+		return result;
 
 	/* This code looks awful: what it's doing is making sure an
 	 * ILLEGAL REQUEST sense return identifies the actual command
@@ -2186,13 +2186,15 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 			data->block_descriptor_length = buffer[3];
 		}
 		data->header_length = header_length;
+		result = 0;
 	} else if ((status_byte(result) == CHECK_CONDITION) &&
 		   scsi_sense_valid(sshdr) &&
 		   sshdr->sense_key == UNIT_ATTENTION && retry_count) {
 		retry_count--;
 		goto retry;
 	}
-
+	if (result > 0)
+		result = -EIO;
 	return result;
 }
 EXPORT_SYMBOL(scsi_mode_sense);

drivers/scsi/scsi_transport_sas.c

@@ -1229,16 +1229,15 @@ int sas_read_port_mode_page(struct scsi_device *sdev)
 	char *buffer = kzalloc(BUF_SIZE, GFP_KERNEL), *msdata;
 	struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
 	struct scsi_mode_data mode_data;
-	int res, error;
+	int error;
 
 	if (!buffer)
 		return -ENOMEM;
 
-	res = scsi_mode_sense(sdev, 1, 0x19, buffer, BUF_SIZE, 30*HZ, 3,
+	error = scsi_mode_sense(sdev, 1, 0x19, buffer, BUF_SIZE, 30*HZ, 3,
 				&mode_data, NULL);
 
-	error = -EINVAL;
-	if (!scsi_status_is_good(res))
+	if (error)
 		goto out;
 
 	msdata = buffer +  mode_data.header_length +

drivers/scsi/sd.c

@@ -2670,18 +2670,18 @@ sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
 		 * 5: Illegal Request, Sense Code 24: Invalid field in
 		 * CDB.
 		 */
-		if (!scsi_status_is_good(res))
+		if (res < 0)
 			res = sd_do_mode_sense(sdkp, 0, 0, buffer, 4, &data, NULL);
 
 		/*
 		 * Third attempt: ask 255 bytes, as we did earlier.
 		 */
-		if (!scsi_status_is_good(res))
+		if (res < 0)
 			res = sd_do_mode_sense(sdkp, 0, 0x3F, buffer, 255,
 					       &data, NULL);
 	}
 
-	if (!scsi_status_is_good(res)) {
+	if (res < 0) {
 		sd_first_printk(KERN_WARNING, sdkp,
 			  "Test WP failed, assume Write Enabled\n");
 	} else {
@@ -2742,7 +2742,7 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
 	res = sd_do_mode_sense(sdkp, dbd, modepage, buffer, first_len,
 			&data, &sshdr);
 
-	if (!scsi_status_is_good(res))
+	if (res < 0)
 		goto bad_sense;
 
 	if (!data.header_length) {
@@ -2774,7 +2774,7 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
 		res = sd_do_mode_sense(sdkp, dbd, modepage, buffer, len,
 				&data, &sshdr);
 
-	if (scsi_status_is_good(res)) {
+	if (!res) {
 		int offset = data.header_length + data.block_descriptor_length;
 
 		while (offset < len) {
@@ -2892,7 +2892,7 @@ static void sd_read_app_tag_own(struct scsi_disk *sdkp, unsigned char *buffer)
 	res = scsi_mode_sense(sdp, 1, 0x0a, buffer, 36, SD_TIMEOUT,
 			      sdkp->max_retries, &data, &sshdr);
 
-	if (!scsi_status_is_good(res) || !data.header_length ||
+	if (res < 0 || !data.header_length ||
 	    data.length < 6) {
 		sd_first_printk(KERN_WARNING, sdkp,
 			  "getting Control mode page failed, assume no ATO\n");

drivers/scsi/sr.c

@@ -911,7 +911,7 @@ static void get_capabilities(struct scsi_cd *cd)
 	rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, ms_len,
 			     SR_TIMEOUT, 3, &data, NULL);
 
-	if (!scsi_status_is_good(rc) || data.length > ms_len ||
+	if (rc < 0 || data.length > ms_len ||
 	    data.header_length + data.block_descriptor_length > data.length) {
 		/* failed, drive doesn't have capabilities mode page */
 		cd->cdi.speed = 1;