uevent: use add_uevent_var() instead of open coding it

Make use of add_uevent_var() instead of (often incorrectly) open coding it.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Eric Rannaud <eric.rannaud@gmail.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index bf37cdf..5aac0ec 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -423,27 +423,25 @@
 		       char *buffer, int buffer_size)
 {
 	struct ap_device *ap_dev = to_ap_dev(dev);
-	int length;
+	int retval = 0, length = 0, i = 0;
 
 	if (!ap_dev)
 		return -ENODEV;
 
 	/* Set up DEV_TYPE environment variable. */
-	envp[0] = buffer;
-	length = scnprintf(buffer, buffer_size, "DEV_TYPE=%04X",
-			   ap_dev->device_type);
-	if (buffer_size - length <= 0)
-		return -ENOMEM;
-	buffer += length;
-	buffer_size -= length;
+	retval = add_uevent_var(envp, num_envp, &i,
+				buffer, buffer_size, &length,
+				"DEV_TYPE=%04X", ap_dev->device_type);
+	if (retval)
+		return retval;
+
 	/* Add MODALIAS= */
-	envp[1] = buffer;
-	length = scnprintf(buffer, buffer_size, "MODALIAS=ap:t%02X",
-			   ap_dev->device_type);
-	if (buffer_size - length <= 0)
-		return -ENOMEM;
-	envp[2] = NULL;
-	return 0;
+	retval = add_uevent_var(envp, num_envp, &i,
+				buffer, buffer_size, &length,
+				"MODALIAS=ap:t%02X", ap_dev->device_type);
+
+	envp[i] = NULL;
+	return retval;
 }
 
 static struct bus_type ap_bus_type = {