staging: unisys: visorbus: add error handling to error_show

Don't just drop the error from visorchannel_read on the floor, report it.
Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: Reviewed-by: Tim Sell <timothy.sell@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/unisys/visorbus/visorchipset.c

@@ -170,11 +170,14 @@ static ssize_t error_show(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
 	u32 error = 0;
+	int err;
 
-	visorchannel_read(chipset_dev->controlvm_channel,
-			  offsetof(struct spar_controlvm_channel_protocol,
-				   installation_error),
-			  &error, sizeof(u32));
+	err = visorchannel_read(chipset_dev->controlvm_channel,
+				offsetof(struct spar_controlvm_channel_protocol,
+					 installation_error),
+				&error, sizeof(u32));
+	if (err)
+		return err;
 	return sprintf(buf, "%i\n", error);
 }