Core: Cache device descriptors in the core

Discussion: It is necessary to cache the device descriptor in the core to
support reading the descriptors after a device is disconnected. We could
either 1) allow each backend to handle this caching (which would most
certainly duplicate code), or 2) cache the descritors when a device
is added. This patch does the later.

Further discussion: It might be beneficial to cache more than just the
device descriptors in the core. It might also be worthwhile caching the
configuration and BOS descriptors as well.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

libusb/core.c

@@ -537,15 +537,13 @@ struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
 int usbi_sanitize_device(struct libusb_device *dev)
 {
 	int r;
-	unsigned char raw_desc[DEVICE_DESC_LENGTH];
 	uint8_t num_configurations;
-	int host_endian;
 
-	r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
+	r = usbi_device_cache_descriptor(dev);
 	if (r < 0)
 		return r;
 
-	num_configurations = raw_desc[DEVICE_DESC_LENGTH - 1];
+	num_configurations = dev->device_descriptor.bNumConfigurations;
 	if (num_configurations > USB_MAXCONFIG) {
 		usbi_err(DEVICE_CTX(dev), "too many configurations");
 		return LIBUSB_ERROR_IO;

libusb/descriptor.c

@@ -437,6 +437,25 @@ err:
 	return r;
 }
 
+int usbi_device_cache_descriptor(libusb_device *dev)
+{
+	int r, host_endian;
+
+	r = usbi_backend->get_device_descriptor(dev, (unsigned char *) &dev->device_descriptor,
+						&host_endian);
+	if (r < 0)
+		return r;
+
+	if (!host_endian) {
+		dev->device_descriptor.bcdUSB = libusb_le16_to_cpu(dev->device_descriptor.bcdUSB);
+		dev->device_descriptor.idVendor = libusb_le16_to_cpu(dev->device_descriptor.idVendor);
+		dev->device_descriptor.idProduct = libusb_le16_to_cpu(dev->device_descriptor.idProduct);
+		dev->device_descriptor.bcdDevice = libusb_le16_to_cpu(dev->device_descriptor.bcdDevice);
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
 /** \ingroup desc
  * Get the USB device descriptor for a given device.
  *
@@ -449,22 +468,9 @@ err:
 int API_EXPORTED libusb_get_device_descriptor(libusb_device *dev,
 	struct libusb_device_descriptor *desc)
 {
-	unsigned char raw_desc[DEVICE_DESC_LENGTH];
-	int host_endian = 0;
-	int r;
-
 	usbi_dbg("");
-	r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
-	if (r < 0)
-		return r;
-
-	memcpy((unsigned char *) desc, raw_desc, sizeof(raw_desc));
-	if (!host_endian) {
-		desc->bcdUSB = libusb_le16_to_cpu(desc->bcdUSB);
-		desc->idVendor = libusb_le16_to_cpu(desc->idVendor);
-		desc->idProduct = libusb_le16_to_cpu(desc->idProduct);
-		desc->bcdDevice = libusb_le16_to_cpu(desc->bcdDevice);
-	}
+	memcpy((unsigned char *) desc, (unsigned char *) &dev->device_descriptor,
+	       sizeof (dev->device_descriptor));
 	return 0;
 }
 

libusb/libusbi.h

@@ -288,6 +288,9 @@ struct libusb_device {
 
 	struct list_head list;
 	unsigned long session_data;
+
+	struct libusb_device_descriptor device_descriptor;
+
 	unsigned char os_priv[0];
 };
 
@@ -394,6 +397,7 @@ int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer);
 
 int usbi_parse_descriptor(unsigned char *source, const char *descriptor,
 	void *dest, int host_endian);
+int usbi_device_cache_descriptor(libusb_device *dev);
 int usbi_get_config_index_by_value(struct libusb_device *dev,
 	uint8_t bConfigurationValue, int *idx);
 

libusb/os/windows_usb.c

@@ -1170,6 +1170,8 @@ static int init_device(struct libusb_device* dev, struct libusb_device* parent_d
 		force_hcd_device_descriptor(dev);
 	}
 
+	usbi_sanitize_device(dev);
+
 	usbi_dbg("(bus: %d, addr: %d, depth: %d, port: %d): '%s'",
 		dev->bus_number, dev->device_address, priv->depth, priv->port, device_id);
 

libusb/version_nano.h

@@ -1 +1 @@
-#define LIBUSB_NANO 10649
+#define LIBUSB_NANO 10650