ftdi->readbuffer_offset = 0;
ftdi->readbuffer_remaining = 0;
ftdi->writebuffer_chunksize = 4096;
+ ftdi->max_packet_size = 0;
ftdi->interface = 0;
ftdi->index = 0;
}
/**
+ * Internal function to determine the maximum packet size.
+ * \param ftdi pointer to ftdi_context
+ * \param dev libusb usb_dev to use
+ * \retval Maximum packet size for this device
+ */
+static unsigned int _ftdi_determine_max_packet_size(struct ftdi_context *ftdi, struct usb_device *dev)
+{
+ unsigned int packet_size;
+
+ // Determine maximum packet size. Init with default value.
+ // New hi-speed devices from FTDI use a packet size of 512 bytes
+ // but could be connected to a normal speed USB hub -> 64 bytes packet size.
+ if (ftdi->type == TYPE_2232H || ftdi->type == TYPE_4232H)
+ packet_size = 512;
+ else
+ packet_size = 64;
+
+ if (dev->descriptor.bNumConfigurations > 0 && dev->config)
+ {
+ struct usb_config_descriptor config = dev->config[0];
+
+ if (ftdi->interface < config.bNumInterfaces)
+ {
+ struct usb_interface interface = config.interface[ftdi->interface];
+ if (interface.num_altsetting > 0)
+ {
+ struct usb_interface_descriptor descriptor = interface.altsetting[0];
+ if (descriptor.bNumEndpoints > 0)
+ {
+ packet_size = descriptor.endpoint[0].wMaxPacketSize;
+ }
+ }
+ }
+ }
+
+ return packet_size;
+}
+
+/**
Opens a ftdi device given by a usb_device.
\param ftdi pointer to ftdi_context
break;
}
+ // Determine maximum packet size
+ ftdi->max_packet_size = _ftdi_determine_max_packet_size(ftdi, dev);
+
if (ftdi_set_baudrate (ftdi, 9600) != 0)
{
ftdi_usb_close_internal (ftdi);
int ftdi_read_data(struct ftdi_context *ftdi, unsigned char *buf, int size)
{
int offset = 0, ret = 1, i, num_of_chunks, chunk_remains;
- int packet_size;
+ int packet_size = ftdi->max_packet_size;
- // New hi-speed devices from FTDI use a packet size of 512 bytes
- if (ftdi->type == TYPE_2232H || ftdi->type == TYPE_4232H)
- packet_size = 512;
- else
- packet_size = 64;
+ // Packet size sanity check (avoid division by zero)
+ if (packet_size == 0)
+ ftdi_error_return(-1, "max_packet_size is bogus (zero)");
// everything we want is still in the readbuffer?
if (size <= ftdi->readbuffer_remaining)