s390/cio: Export information about Endpoint-Security Capability

Add a new sysfs attribute 'esc' per chpid. This new attribute exports
the Endpoint-Security-Capability byte of channel-path description block,
which could be 0-None, 1-Authentication, 2 and 3-Encryption.

For example:
$ cat /sys/devices/css0/chp0.34/esc
0

[vneethv@linux.ibm.com: cleaned-up & modified description]
Signed-off-by: NSebastian Ott <sebott@linux.ibm.com>
Signed-off-by: NVineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: NStefan Haberland <sth@linux.ibm.com>
Reviewed-by: NJan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: NPeter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Acked-by: NVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/s390/cio/chp.c

@@ -384,6 +384,20 @@ static ssize_t chp_chid_external_show(struct device *dev,
 }
 static DEVICE_ATTR(chid_external, 0444, chp_chid_external_show, NULL);
 
+static ssize_t chp_esc_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct channel_path *chp = to_channelpath(dev);
+	ssize_t rc;
+
+	mutex_lock(&chp->lock);
+	rc = sprintf(buf, "%x\n", chp->desc_fmt1.esc);
+	mutex_unlock(&chp->lock);
+
+	return rc;
+}
+static DEVICE_ATTR(esc, 0444, chp_esc_show, NULL);
+
 static ssize_t util_string_read(struct file *filp, struct kobject *kobj,
 				struct bin_attribute *attr, char *buf,
 				loff_t off, size_t count)
@@ -414,6 +428,7 @@ static struct attribute *chp_attrs[] = {
 	&dev_attr_shared.attr,
 	&dev_attr_chid.attr,
 	&dev_attr_chid_external.attr,
+	&dev_attr_esc.attr,
 	NULL,
 };
 static struct attribute_group chp_attr_group = {

drivers/s390/cio/chsc.h

@@ -27,7 +27,8 @@ struct channel_path_desc_fmt1 {
 	u8 lsn;
 	u8 desc;
 	u8 chpid;
-	u32:24;
+	u32:16;
+	u8 esc;
 	u8 chpp;
 	u32 unused[2];
 	u16 chid;