Add private storage pointer to struct sr_channel.

include/libsigrok/libsigrok.h

@@ -469,6 +469,8 @@ struct sr_channel {
 	gboolean enabled;
 	/** Name of channel. */
 	char *name;
+	/** Private data for driver use. */
+	void *priv;
 };
 
 /** Structure for groups of channels that have common properties. */

src/device.c

@@ -251,6 +251,7 @@ SR_PRIV void sr_dev_inst_free(struct sr_dev_inst *sdi)
 	for (l = sdi->channels; l; l = l->next) {
 		ch = l->data;
 		g_free(ch->name);
+		g_free(ch->priv);
 		g_free(ch);
 	}
 	g_slist_free(sdi->channels);