scsi: target: add device vendor_id configfs attribute

The vendor_id attribute will allow for the modification of the T10 Vendor
Identification string returned in inquiry responses. Its value can be
viewed and modified via the ConfigFS path at:

target/core/$backstore/$name/wwn/vendor_id

"LIO-ORG" remains the default value, which is set when the backstore device
is enabled.

[mkp: corrected VPD page number]
Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_configfs.c

@@ -1225,6 +1225,74 @@ static struct t10_wwn *to_t10_wwn(struct config_item *item)
 	return container_of(to_config_group(item), struct t10_wwn, t10_wwn_group);
 }
 
+/*
+ * STANDARD and VPD page 0x83 T10 Vendor Identification
+ */
+static ssize_t target_wwn_vendor_id_show(struct config_item *item,
+		char *page)
+{
+	return sprintf(page, "%s\n", &to_t10_wwn(item)->vendor[0]);
+}
+
+static ssize_t target_wwn_vendor_id_store(struct config_item *item,
+		const char *page, size_t count)
+{
+	struct t10_wwn *t10_wwn = to_t10_wwn(item);
+	struct se_device *dev = t10_wwn->t10_dev;
+	/* +2 to allow for a trailing (stripped) '\n' and null-terminator */
+	unsigned char buf[INQUIRY_VENDOR_LEN + 2];
+	char *stripped = NULL;
+	size_t len;
+	int i;
+
+	len = strlcpy(buf, page, sizeof(buf));
+	if (len < sizeof(buf)) {
+		/* Strip any newline added from userspace. */
+		stripped = strstrip(buf);
+		len = strlen(stripped);
+	}
+	if (len > INQUIRY_VENDOR_LEN) {
+		pr_err("Emulated T10 Vendor Identification exceeds"
+			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
+			"\n");
+		return -EOVERFLOW;
+	}
+
+	/*
+	 * SPC 4.3.1:
+	 * ASCII data fields shall contain only ASCII printable characters (i.e.,
+	 * code values 20h to 7Eh) and may be terminated with one or more ASCII
+	 * null (00h) characters.
+	 */
+	for (i = 0; i < len; i++) {
+		if ((stripped[i] < 0x20) || (stripped[i] > 0x7E)) {
+			pr_err("Emulated T10 Vendor Identification contains"
+				" non-ASCII-printable characters\n");
+			return -EINVAL;
+		}
+	}
+
+	/*
+	 * Check to see if any active exports exist.  If they do exist, fail
+	 * here as changing this information on the fly (underneath the
+	 * initiator side OS dependent multipath code) could cause negative
+	 * effects.
+	 */
+	if (dev->export_count) {
+		pr_err("Unable to set T10 Vendor Identification while"
+			" active %d exports exist\n", dev->export_count);
+		return -EINVAL;
+	}
+
+	BUILD_BUG_ON(sizeof(dev->t10_wwn.vendor) != INQUIRY_VENDOR_LEN + 1);
+	strlcpy(dev->t10_wwn.vendor, stripped, sizeof(dev->t10_wwn.vendor));
+
+	pr_debug("Target_Core_ConfigFS: Set emulated T10 Vendor Identification:"
+		 " %s\n", dev->t10_wwn.vendor);
+
+	return count;
+}
+
 /*
  * VPD page 0x80 Unit serial
  */
@@ -1371,6 +1439,7 @@ DEF_DEV_WWN_ASSOC_SHOW(vpd_assoc_target_port, 0x10);
 /* VPD page 0x83 Association: SCSI Target Device */
 DEF_DEV_WWN_ASSOC_SHOW(vpd_assoc_scsi_target_device, 0x20);
 
+CONFIGFS_ATTR(target_wwn_, vendor_id);
 CONFIGFS_ATTR(target_wwn_, vpd_unit_serial);
 CONFIGFS_ATTR_RO(target_wwn_, vpd_protocol_identifier);
 CONFIGFS_ATTR_RO(target_wwn_, vpd_assoc_logical_unit);
@@ -1378,6 +1447,7 @@ CONFIGFS_ATTR_RO(target_wwn_, vpd_assoc_target_port);
 CONFIGFS_ATTR_RO(target_wwn_, vpd_assoc_scsi_target_device);
 
 static struct configfs_attribute *target_core_dev_wwn_attrs[] = {
+	&target_wwn_attr_vendor_id,
 	&target_wwn_attr_vpd_unit_serial,
 	&target_wwn_attr_vpd_protocol_identifier,
 	&target_wwn_attr_vpd_assoc_logical_unit,