From: Alexandru Gagniuc <redacted>
Date: Thu, 22 Nov 2012 01:30:26 +0000 (-0600)
Subject: radioshack-dmm: Check for valid mode before calculating checksum
X-Git-Tag: dsupstream~530
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=2ecc5d432fd17127fd221ca4940f9617569911d1;p=libsigrok.git

radioshack-dmm: Check for valid mode before calculating checksum

The packet mode byte is akin to a signature. If that is invalid, there's
no point in calculating the checksum, so check the mode first.

Signed-off-by: Alexandru Gagniuc <redacted>
---

diff --git a/hardware/radioshack-dmm/protocol.c b/hardware/radioshack-dmm/protocol.c
index de925b56..f74e7017 100644
--- a/hardware/radioshack-dmm/protocol.c
+++ b/hardware/radioshack-dmm/protocol.c
@@ -176,10 +176,14 @@ static gboolean selection_good(const struct rs_22_812_packet *rs_packet)
  */
 SR_PRIV gboolean rs_22_812_packet_valid(const struct rs_22_812_packet *rs_packet)
 {
-	if (!checksum_valid(rs_packet))
+	/*
+	 * Check for valid mode first, before calculating the checksum.
+	 * No point calculating the checksum, if we know we'll reject the packet
+	 * */
+	if (!(rs_packet->mode < MODE_INVALID))
 		return FALSE;
 
-	if (!(rs_packet->mode < MODE_INVALID))
+	if (!checksum_valid(rs_packet))
 		return FALSE;
 
 	if (!selection_good(rs_packet))