serial-lcr: add support for packet request

Some meters require the reception of a request before they provide
acquisition data. Add support for the chip driver's .packet_request()
routine, and timeout handling in the serial-lcr driver. This follows
the serial-dmm model.

src/hardware/serial-lcr/api.c

@@ -135,8 +135,15 @@ static GSList *scan(struct sr_dev_driver *di, GSList *options)
 	 * send data periodically. So we check if the packets match the
 	 * probed device's expected format.
 	 */
-	serial_flush(serial);
 	devices = NULL;
+	serial_flush(serial);
+	if (lcr->packet_request) {
+		ret = lcr->packet_request(serial);
+		if (ret < 0) {
+			sr_err("Failed to request packet: %d.", ret);
+			goto scan_cleanup;
+		}
+	}
 	len = sizeof(buf);
 	ret = serial_stream_detect(serial, buf, &len,
 		lcr->packet_size, lcr->packet_valid, 3000);
@@ -329,6 +336,7 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
 		}, \
 		vendor, model, ES51919_CHANNEL_COUNT, NULL, \
 		ES51919_COMM_PARAM, ES51919_PACKET_SIZE, \
+		0, NULL, \
 		es51919_packet_valid, es51919_packet_parse, \
 		NULL, NULL, es51919_config_list, \
 	}).di

src/hardware/serial-lcr/protocol.c

@@ -148,10 +148,42 @@ static int handle_new_data(struct sr_dev_inst *sdi)
 	return SR_OK;
 }
 
+static int handle_timeout(struct sr_dev_inst *sdi)
+{
+	struct dev_context *devc;
+	const struct lcr_info *lcr;
+	struct sr_serial_dev_inst *serial;
+	int64_t now;
+	int ret;
+
+	devc = sdi->priv;
+	lcr = devc->lcr_info;
+
+	if (!lcr->packet_request)
+		return SR_OK;
+
+	now = g_get_monotonic_time();
+	if (devc->req_next_at && now < devc->req_next_at)
+		return SR_OK;
+
+	serial = sdi->conn;
+	ret = lcr->packet_request(serial);
+	if (ret < 0) {
+		sr_err("Failed to request packet: %d.", ret);
+		return ret;
+	}
+
+	if (lcr->req_timeout_ms)
+		devc->req_next_at = now + lcr->req_timeout_ms * 1000;
+
+	return SR_OK;
+}
+
 SR_PRIV int lcr_receive_data(int fd, int revents, void *cb_data)
 {
 	struct sr_dev_inst *sdi;
 	struct dev_context *devc;
+	int ret;
 
 	(void)fd;
 
@@ -161,10 +193,13 @@ SR_PRIV int lcr_receive_data(int fd, int revents, void *cb_data)
 		return TRUE;
 
 	if (revents == G_IO_IN)
-		handle_new_data(sdi);
+		ret = handle_new_data(sdi);
-
+	else
+		ret = handle_timeout(sdi);
 	if (sr_sw_limits_check(&devc->limits))
 		sr_dev_acquisition_stop(sdi);
+	if (ret != SR_OK)
+		return FALSE;
 
 	return TRUE;
 }

src/hardware/serial-lcr/protocol.h

@@ -36,6 +36,8 @@ struct lcr_info {
 	const char **channel_formats;
 	const char *comm;
 	size_t packet_size;
+	int64_t req_timeout_ms;
+	int (*packet_request)(struct sr_serial_dev_inst *serial);
 	gboolean (*packet_valid)(const uint8_t *pkt);
 	int (*packet_parse)(const uint8_t *pkt, float *value,
 		struct sr_datafeed_analog *analog, void *info);
@@ -60,6 +62,7 @@ struct dev_context {
 	struct lcr_parse_info parse_info;
 	uint64_t output_freq;
 	const char *circuit_model;
+	int64_t req_next_at;
 };
 
 SR_PRIV int lcr_receive_data(int fd, int revents, void *cb_data);