sigrok plugin: constify

diff --git a/src/sigrok.c b/src/sigrok.c
index 487f31a..ad5c70c 100644 (file)
--- a/src/sigrok.c
+++ b/src/sigrok.c
@@ -136,9 +136,9 @@ static int sigrok_config(oconfig_item_t *ci)
        return 0;
 }
 
-static char *sigrok_value_type(const struct sr_datafeed_analog *analog)
+static const char *sigrok_value_type(const struct sr_datafeed_analog *analog)
 {
-       char *s;
+       const char *s;
 
        if (analog->mq == SR_MQ_VOLTAGE)
                s = "voltage";