show: Format channel output when no channel is available

[sigrok-cli.git] / device.c

diff --git a/device.c b/device.c
index 19192ecbb0b69b404529df45d374be955d1962c9..7da744431154c134b5bee897bc24f817cc774e46 100644 (file)
--- a/device.c
+++ b/device.c
@@ -63,16 +63,37 @@ GSList *device_scan(void)
        return devices;
 }
 
-struct sr_channel_group *select_channel_group(struct sr_dev_inst *sdi)
+/**
+ * Lookup a channel group from its name.
+ *
+ * Uses the caller specified channel group name, or a previously stored
+ * option value as a fallback. Returns a reference to the channel group
+ * when the lookup succeeded, or #NULL after lookup failure, as well as
+ * #NULL for the global channel group (the device).
+ *
+ * Accepts either #NULL pointer, or an empty string, or the "global"
+ * literal to address the global channel group (the device). Emits an
+ * error message when the lookup failed while a name was specified.
+ *
+ * @param[in] sdi Device instance.
+ * @param[in] cg_name Caller provided channel group name.
+ *
+ * @returns The channel group, or #NULL for failed lookup.
+ */
+struct sr_channel_group *lookup_channel_group(struct sr_dev_inst *sdi,
+       const char *cg_name)
 {
        struct sr_channel_group *cg;
        GSList *l, *channel_groups;
 
-       if (!opt_channel_group)
+       if (!cg_name)
+               cg_name = opt_channel_group;
+       if (cg_name && g_ascii_strcasecmp(cg_name, "global") == 0)
+               cg_name = NULL;
+       if (!cg_name || !*cg_name)
                return NULL;
 
        channel_groups = sr_dev_inst_channel_groups_get(sdi);
-
        if (!channel_groups) {
                g_critical("This device does not have any channel groups.");
                return NULL;
@@ -80,11 +101,11 @@ struct sr_channel_group *select_channel_group(struct sr_dev_inst *sdi)
 
        for (l = channel_groups; l; l = l->next) {
                cg = l->data;
-               if (!g_ascii_strcasecmp(opt_channel_group, cg->name)) {
-                       return cg;
-               }
+               if (g_ascii_strcasecmp(cg_name, cg->name) != 0)
+                       continue;
+               return cg;
        }
-       g_critical("Invalid channel group '%s'", opt_channel_group);
+       g_critical("Invalid channel group '%s'", cg_name);
 
        return NULL;
 }