From: Gerhard Sittig <redacted>
Date: Sat, 22 Jan 2022 11:12:17 +0000 (+0100)
Subject: kingst-la2016: rephrase manufacture date and device type support
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=43d2e52fe1c0c51639b69603f285d534a34c4f09;p=libsigrok.git

kingst-la2016: rephrase manufacture date and device type support

The "purchase date" reader asssumed a little endian host when reading
16bit data from the device. Use endianess aware readers instead. Which
also unobfuscates the YY and MM positions in the byte array (comments
were plenty, but the code would not reflect what happened). Rephrase
the consistency check in the date and magic code paths (the inverted
bits), better reflect the XOR approach.

Prefer the "manufacture date" term since that's what the vendor is aware
of, while the customer's date of purchase or the dealer's shelf time are
unknown to vendors.

Split complex invocation from caller's flow control to improve
readability of the code path. Which also trims text line length.
---

diff --git a/src/hardware/kingst-la2016/protocol.c b/src/hardware/kingst-la2016/protocol.c
index b5e70b3d..609c8aa2 100644
--- a/src/hardware/kingst-la2016/protocol.c
+++ b/src/hardware/kingst-la2016/protocol.c
@@ -1106,7 +1106,9 @@ SR_PRIV int la2016_init_device(const struct sr_dev_inst *sdi)
 	struct dev_context *devc;
 	uint16_t state;
 	uint8_t buf[8];
-	int16_t purchase_date_bcd[2];
+	const uint8_t *rdptr;
+	uint8_t date_yy, date_mm;
+	uint8_t dinv_yy, dinv_mm;
 	uint8_t magic;
 	const char *bitstream_fn;
 	int ret;
@@ -1114,20 +1116,24 @@ SR_PRIV int la2016_init_device(const struct sr_dev_inst *sdi)
 	devc = sdi->priv;
 
 	/*
-	 * Four EEPROM bytes at offset 0x20 are purchase year and month
-	 * in BCD format, with 16bit complemented checksum. For example
-	 * 20 04 df fb translates to 2020-04. This can help identify the
-	 * age of devices when unknown magic numbers are seen.
+	 * Four EEPROM bytes at offset 0x20 are the manufacturing date,
+	 * year and month in BCD format, followed by inverted values for
+	 * consistency checks. For example bytes 20 04 df fb translate
+	 * to 2020-04. This information can help identify the vintage of
+	 * devices when unknown magic numbers are seen.
 	 */
-	if ((ret = ctrl_in(sdi, CMD_EEPROM, 0x20, 0, purchase_date_bcd, sizeof(purchase_date_bcd))) != SR_OK) {
-		sr_err("Cannot read purchase date in EEPROM.");
+	ret = ctrl_in(sdi, CMD_EEPROM, 0x20, 0, buf, 4 * sizeof(uint8_t));
+	if (ret != SR_OK) {
+		sr_err("Cannot read manufacture date in EEPROM.");
 	} else {
-		sr_dbg("Purchase date: 20%02hx-%02hx.",
-			(purchase_date_bcd[0]) & 0xff,
-			(purchase_date_bcd[0] >> 8) & 0xff);
-		if (purchase_date_bcd[0] != (0x0ffff & ~purchase_date_bcd[1])) {
-			sr_err("Purchase date fails checksum test.");
-		}
+		rdptr = &buf[0];
+		date_yy = read_u8_inc(&rdptr);
+		date_mm = read_u8_inc(&rdptr);
+		dinv_yy = read_u8_inc(&rdptr);
+		dinv_mm = read_u8_inc(&rdptr);
+		sr_info("Manufacture date: 20%02hx-%02hx.", date_yy, date_mm);
+		if ((date_mm ^ dinv_mm) != 0xff || (date_yy ^ dinv_yy) != 0xff)
+			sr_warn("Manufacture date fails checksum test.");
 	}
 
 	/*
@@ -1172,17 +1178,18 @@ SR_PRIV int la2016_init_device(const struct sr_dev_inst *sdi)
 		sr_err("Cannot read EEPROM device identifier bytes.");
 		return ret;
 	}
-
-	magic = 0;
-	if (buf[0] == (0xff & ~buf[1])) {
+	if ((buf[0] ^ buf[1]) == 0xff) {
 		/* Primary copy of magic passes complement check. */
+		sr_dbg("Using primary copy of device type magic number.");
 		magic = buf[0];
-	} else if (buf[4] == (0xff & ~buf[5])) {
+	} else if ((buf[4] ^ buf[5]) == 0xff) {
 		/* Backup copy of magic passes complement check. */
 		sr_dbg("Using backup copy of device type magic number.");
 		magic = buf[4];
+	} else {
+		sr_err("Cannot find consistent device type identification.");
+		magic = 0;
 	}
-
 	sr_dbg("Device type: magic number is %hhu.", magic);
 
 	/* Select the FPGA bitstream depending on the model. */