Virtual session: Workaround for SR_CONF_CAPTUREFILE (#944)

This is a (hopefully temporary) workaround for the
SR_CONF_CAPTUREFILE mechanism. The value for
vdev->capturefile is set by this, however only once
via stream_session_data().
During stream processing in stream_session_data(),
capturefile may receive new values - e.g. when there
are multiple logic files or if there is analog data.
With that, the initially set capturefile is overwritten.

When re-loading the file, we are then running into
issues because we don't know what the initial value was.
As all .sr files use "logic-1" by default and, we
simulate the behavior of stream_session_data() and
assign this name to capturefile if there are logic
channels present.

With this change, all three kinds of files reload
as expected: logic only, analog only and mixed signal.
For this reason, it's a short-term fix for #944.

src/session_driver.c

@@ -124,7 +124,17 @@ static gboolean stream_session_data(struct sr_dev_inst *sdi)
 			} else {
 				/* We got all the chunks, finish up. */
 				g_free(vdev->capturefile);
-				vdev->capturefile = NULL;
+
+				/* If the file has logic channels, the initial value for
+				 * capturefile is set by stream_session_data() - however only
+				 * once. In order to not mess this mechanism up, we simulate
+				 * this here if needed. For purely analog files, capturefile
+				 * is not set.
+				 */
+				if (vdev->num_logic_channels)
+					vdev->capturefile = g_strdup("logic-1");
+				else
+					vdev->capturefile = NULL;
 				return FALSE;
 			}
 		}