introduce api function to read usb string descriptors

This API allows to read manufacturer and product names as well as the
serial number advertized by the device on the bus.

include/rtl-sdr.h

@@ -33,6 +33,22 @@ RTLSDR_API uint32_t rtlsdr_get_device_count(void);
 
 RTLSDR_API const char* rtlsdr_get_device_name(uint32_t index);
 
+/*!
+ * Get USB device strings.
+ *
+ * NOTE: The string arguments must provide space for up to 256 bytes.
+ *
+ * \param index the device index
+ * \param manufact manufacturer name, may be NULL
+ * \param product product name, may be NULL
+ * \param serial serial number, may be NULL
+ * \return 0 on success
+ */
+RTLSDR_API int rtlsdr_get_device_usb_strings(uint32_t index,
+					     char *manufact,
+					     char *product,
+					     char *serial);
+
 RTLSDR_API int rtlsdr_open(rtlsdr_dev_t **dev, uint32_t index);
 
 RTLSDR_API int rtlsdr_close(rtlsdr_dev_t *dev);
@@ -69,6 +85,20 @@ RTLSDR_API int rtlsdr_set_xtal_freq(rtlsdr_dev_t *dev, uint32_t rtl_freq,
 RTLSDR_API int rtlsdr_get_xtal_freq(rtlsdr_dev_t *dev, uint32_t *rtl_freq,
 				    uint32_t *tuner_freq);
 
+/*!
+ * Get USB device strings.
+ *
+ * NOTE: The string arguments must provide space for up to 256 bytes.
+ *
+ * \param dev the device handle given by rtlsdr_open()
+ * \param manufact manufacturer name, may be NULL
+ * \param product product name, may be NULL
+ * \param serial serial number, may be NULL
+ * \return 0 on success
+ */
+RTLSDR_API int rtlsdr_get_usb_strings(rtlsdr_dev_t *dev, char *manufact,
+				      char *product, char *serial);
+
 RTLSDR_API int rtlsdr_set_center_freq(rtlsdr_dev_t *dev, uint32_t freq);
 
 /*!

src/librtlsdr.c

@@ -571,6 +571,47 @@ int rtlsdr_get_xtal_freq(rtlsdr_dev_t *dev, uint32_t *rtl_freq, uint32_t *tuner_
 	return 0;
 }
 
+int rtlsdr_get_usb_strings(rtlsdr_dev_t *dev, char *manufact, char *product,
+			    char *serial)
+{
+	struct libusb_device_descriptor dd;
+	libusb_device *device = NULL;
+	const int buf_max = 256;
+	int r = 0;
+
+	if (!dev || !dev->devh)
+		return -1;
+
+	device = libusb_get_device(dev->devh);
+
+	r = libusb_get_device_descriptor(device, &dd);
+	if (r < 0)
+		return -1;
+
+	if (manufact) {
+		memset(manufact, 0, buf_max);
+		libusb_get_string_descriptor_ascii(dev->devh, dd.iManufacturer,
+						   (unsigned char *)manufact,
+						   buf_max);
+	}
+
+	if (product) {
+		memset(product, 0, buf_max);
+		libusb_get_string_descriptor_ascii(dev->devh, dd.iProduct,
+						   (unsigned char *)product,
+						   buf_max);
+	}
+
+	if (serial) {
+		memset(serial, 0, buf_max);
+		libusb_get_string_descriptor_ascii(dev->devh, dd.iSerialNumber,
+						   (unsigned char *)serial,
+						   buf_max);
+	}
+
+	return 0;
+}
+
 int rtlsdr_set_center_freq(rtlsdr_dev_t *dev, uint32_t freq)
 {
 	int r = -1;
@@ -815,6 +856,52 @@ const char *rtlsdr_get_device_name(uint32_t index)
 		return "";
 }
 
+int rtlsdr_get_device_usb_strings(uint32_t index, char *manufact,
+				   char *product, char *serial)
+{
+	int r = -2;
+	int i;
+	libusb_context *ctx;
+	libusb_device **list;
+	struct libusb_device_descriptor dd;
+	rtlsdr_dongle_t *device = NULL;
+	rtlsdr_dev_t devt;
+	uint32_t device_count = 0;
+	ssize_t cnt;
+
+	libusb_init(&ctx);
+
+	cnt = libusb_get_device_list(ctx, &list);
+
+	for (i = 0; i < cnt; i++) {
+		libusb_get_device_descriptor(list[i], &dd);
+
+		device = find_known_device(dd.idVendor, dd.idProduct);
+
+		if (device) {
+			device_count++;
+
+			if (index == device_count - 1) {
+				r = libusb_open(list[i], &devt.devh);
+				if (!r) {
+					r = rtlsdr_get_usb_strings(&devt,
+								   manufact,
+								   product,
+								   serial);
+					libusb_close(devt.devh);
+				}
+				break;
+			}
+		}
+	}
+
+	libusb_free_device_list(list, 1);
+
+	libusb_exit(ctx);
+
+	return r;
+}
+
 int rtlsdr_open(rtlsdr_dev_t **out_dev, uint32_t index)
 {
 	int r;

src/rtl_sdr.c

@@ -107,6 +107,7 @@ int main(int argc, char **argv)
 	uint32_t samp_rate = DEFAULT_SAMPLE_RATE;
 	uint32_t out_block_size = DEFAULT_BUF_LENGTH;
 	int device_count;
+	char vendor[256], product[256], serial[256];
 #ifndef _WIN32
 	while ((opt = getopt(argc, argv, "d:f:g:s:b:S::")) != -1) {
 		switch (opt) {
@@ -168,13 +169,14 @@ int main(int argc, char **argv)
 	}
 
 	fprintf(stderr, "Found %d device(s):\n", device_count);
-	for (i = 0; i < device_count; i++)
-		fprintf(stderr, "  %d:  %s\n", i, rtlsdr_get_device_name(i));
+	for (i = 0; i < device_count; i++) {
+		rtlsdr_get_device_usb_strings(i, vendor, product, serial);
+		fprintf(stderr, "  %d:  %s, %s, SN: %s\n", i, vendor, product, serial);
+	}
 	fprintf(stderr, "\n");
 
 	fprintf(stderr, "Using device %d: %s\n",
-		dev_index,
-		rtlsdr_get_device_name(dev_index));
+		dev_index, rtlsdr_get_device_name(dev_index));
 
 	r = rtlsdr_open(&dev, dev_index);
 	if (r < 0) {