From: Gerhard Sittig <redacted>
Date: Sun, 19 Mar 2023 18:21:04 +0000 (+0100)
Subject: rdtech-tc: avoid too eager request retransmission
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=66d58fcb9fdd3a167b8fc6ca19f7f0a007c2ee8f;p=libsigrok.git

rdtech-tc: avoid too eager request retransmission

The sequence of a scan/probe (which exchanges exactly one request and
response pair) before an acquisition (which requests another response,
then keeps re-requesting periodically) resulted in the transmission of
more requests shortly after a request was sent and before any response
started receiving at all. Which then resulted in unexpected lengths and
failed consistency checks for the receive data. This condition stuck
because rdtech-tc does not support the re-synchronization to the input
stream as rdtech-um does.

Defer transmission of requests until after receive data was seen (or
an acquisition start forces their transmission). Tested by repeatedly
running:

  $ sigrok-cli -d rdtech-tc:conn=bt/dialog/$MAC --continuous
---

diff --git a/src/hardware/rdtech-tc/protocol.c b/src/hardware/rdtech-tc/protocol.c
index bef28a93..3dff0d6a 100644
--- a/src/hardware/rdtech-tc/protocol.c
+++ b/src/hardware/rdtech-tc/protocol.c
@@ -202,10 +202,17 @@ SR_PRIV int rdtech_tc_poll(const struct sr_dev_inst *sdi, gboolean force)
 
 	/*
 	 * Don't send the request while receive data is being accumulated.
+	 * Defer request transmission when a previous request has not yet
+	 * seen any response data at all (more probable to happen shortly
+	 * after connecting to the peripheral).
 	 */
 	devc = sdi->priv;
-	if (!force && devc->rdlen)
-		return SR_OK;
+	if (!force) {
+		if (devc->rdlen)
+			return SR_OK;
+		if (!devc->rx_after_tx)
+			return SR_OK;
+	}
 
 	/*
 	 * Send the request when the transmit interval was reached. Or
@@ -228,6 +235,7 @@ SR_PRIV int rdtech_tc_poll(const struct sr_dev_inst *sdi, gboolean force)
 		return SR_ERR;
 	}
 	devc->cmd_sent_at = now;
+	devc->rx_after_tx = 0;
 
 	return SR_OK;
 }
@@ -291,6 +299,7 @@ static int recv_poll_data(struct sr_dev_inst *sdi, struct sr_serial_dev_inst *se
 		if (len == 0)
 			return SR_OK;
 		devc->rdlen += len;
+		devc->rx_after_tx += len;
 	}
 
 	/*
diff --git a/src/hardware/rdtech-tc/protocol.h b/src/hardware/rdtech-tc/protocol.h
index 789b18c2..e495375c 100644
--- a/src/hardware/rdtech-tc/protocol.h
+++ b/src/hardware/rdtech-tc/protocol.h
@@ -62,6 +62,7 @@ struct dev_context {
 	uint8_t buf[RDTECH_TC_RSPBUFSIZE];
 	size_t rdlen;
 	int64_t cmd_sent_at;
+	size_t rx_after_tx;
 };
 
 SR_PRIV int rdtech_tc_probe(struct sr_serial_dev_inst *serial, struct dev_context *devc);