From: Gerhard Sittig <redacted>
Date: Fri, 25 Dec 2020 11:47:01 +0000 (+0100)
Subject: ftdi-la: work around missing USB strings during device probe
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=aa8e4959e24ad1c5fa034f307c417166f26b62b8;p=libsigrok.git

ftdi-la: work around missing USB strings during device probe

Some FTDI chip based products ship with EEPROM content which makes
libftdi fail to lookup the USB strings, which breaks the scan for the
device's presence. The previous implementation was strict and only
accepted the absence of a serial number. This implementation also copes
when vendor and model cannot be gathered from the device, and provides
fallback values based on VID:PID numbers.

Also factor out a magic number for string lengths. Stick with dynamic
allocation since 3x 32bytes would be rather huge a local stack use, and
future maintenance might bump that string length again.

[ gsi: magic number in one spot, bounded string assignment, style nits ]

Submitted-By: Christo Crause <redacted>
---

diff --git a/src/hardware/ftdi-la/api.c b/src/hardware/ftdi-la/api.c
index 85b7df7e..8bb67121 100644
--- a/src/hardware/ftdi-la/api.c
+++ b/src/hardware/ftdi-la/api.c
@@ -111,6 +111,8 @@ static const struct ftdi_chip_desc *chip_descs[] = {
 static void scan_device(struct ftdi_context *ftdic,
 	struct libusb_device *dev, GSList **devices)
 {
+	static const int usb_str_maxlen = 32;
+
 	struct libusb_device_descriptor usb_desc;
 	const struct ftdi_chip_desc *desc;
 	struct dev_context *devc;
@@ -143,14 +145,42 @@ static void scan_device(struct ftdi_context *ftdic,
 
 	devc->desc = desc;
 
-	vendor = g_malloc(32);
-	model = g_malloc(32);
-	serial_num = g_malloc(32);
-	rv = ftdi_usb_get_strings(ftdic, dev, vendor, 32,
-			model, 32, serial_num, 32);
+	vendor = g_malloc(usb_str_maxlen);
+	model = g_malloc(usb_str_maxlen);
+	serial_num = g_malloc(usb_str_maxlen);
+	rv = ftdi_usb_get_strings(ftdic, dev, vendor, usb_str_maxlen,
+			model, usb_str_maxlen, serial_num, usb_str_maxlen);
 	switch (rv) {
 	case 0:
 		break;
+	/* ftdi_usb_get_strings() fails on first miss, hence fall through. */
+	case -7:
+		sr_dbg("The device lacks a manufacturer descriptor.");
+		g_snprintf(vendor, usb_str_maxlen, "Generic");
+		/* FALLTHROUGH */
+	case -8:
+		sr_dbg("The device lacks a product descriptor.");
+		switch (usb_desc.idProduct) {
+		case 0x6001:
+			g_snprintf(model, usb_str_maxlen, "FT232R");
+			break;
+		case 0x6010:
+			g_snprintf(model, usb_str_maxlen, "FT2232H");
+			break;
+		case 0x6011:
+			g_snprintf(model, usb_str_maxlen, "FT4232H");
+			break;
+		case 0x6014:
+			g_snprintf(model, usb_str_maxlen, "FT232H");
+			break;
+		case 0x8a98:
+			g_snprintf(model, usb_str_maxlen, "FT2232H-TUMPA");
+			break;
+		default:
+			g_snprintf(model, usb_str_maxlen, "Unknown");
+			break;
+		}
+		/* FALLTHROUGH */
 	case -9:
 		sr_dbg("The device lacks a serial number.");
 		g_free(serial_num);