From 8c57d8966ea966d23fbc4db77f7a8cdc0623b544 Mon Sep 17 00:00:00 2001 From: Nikias Bassen Date: Fri, 28 Aug 2009 00:05:45 +0200 Subject: [PATCH] New flag LIBUSB_TRANSFER_ZERO_PACKET for terminating bulk transfers This patch fixes the Zero Length Packet issue by allowing the client program to specify the LIBUSB_TRANSFER_ZERO_PACKET flag when calling libusb_submit_transfer when the packet size is a multiple of wMaxPacketSize. This will pass the URB_ZERO_PACKET flag to the appropriate ioctl and thus triggers sending of the packet inside the kernel. Otherwise such a packet would never get sent. --- libusb/libusb.h | 23 ++++++++++++++++++++++- libusb/os/linux_usbfs.c | 3 +++ libusb/os/linux_usbfs.h | 1 + 3 files changed, 26 insertions(+), 1 deletions(-) diff --git a/libusb/libusb.h b/libusb/libusb.h index 1126380..ce7bfcf 100644 --- a/libusb/libusb.h +++ b/libusb/libusb.h @@ -672,7 +672,28 @@ enum libusb_transfer_flags { * If this flag is set, it is illegal to call libusb_free_transfer() * from your transfer callback, as this will result in a double-free * when this flag is acted upon. */ - LIBUSB_TRANSFER_FREE_TRANSFER = 1<<2 + LIBUSB_TRANSFER_FREE_TRANSFER = 1<<2, + + /** Terminate bulk transfer by a zero length URB. + * According to the USB spec the last packet of a bulk transfer _must_ + * be terminated by a zero length URB if it has the exact size of the + * endpoint's maximum packet size (wMaxPacketSize). + * By setting this flag the URB_ZERO_PACKET flag will be set before + * performing IOCTL_USBFS_SUBMITURB. This will trigger sending of the + * mentioned packet which otherwise would never get transmitted. + * + * @note Implementers: You need to read the wMaxPacketSize attribute + * of the usb endpoint you are writing to. If the size of the + * packet you are submitting is a multiple of wMaxPacketSize + * you need to set the LIBUSB_TRANSFER_ZERO_PACKET flag before + * calling libusb_submit_transfer(), something like: + * + * if (length % dev->wMaxPacketSize == 0) { + * xfer->flags |= LIBUSB_TRANSFER_ZERO_PACKET; + * } + * libusb_submit_transfer(xfer); + */ + LIBUSB_TRANSFER_ZERO_PACKET = 1<<3 }; /** \ingroup asyncio diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c index 1280188..1f6c989 100644 --- a/libusb/os/linux_usbfs.c +++ b/libusb/os/linux_usbfs.c @@ -1307,6 +1307,9 @@ static int submit_bulk_transfer(struct usbi_transfer *itransfer, else urb->buffer_length = MAX_BULK_BUFFER_LENGTH; + if (transfer->flags & LIBUSB_TRANSFER_ZERO_PACKET) + urb->flags |= USBFS_URB_ZERO_PACKET; + r = ioctl(dpriv->fd, IOCTL_USBFS_SUBMITURB, urb); if (r < 0) { int j; diff --git a/libusb/os/linux_usbfs.h b/libusb/os/linux_usbfs.h index fdf5e9b..9ed0b4f 100644 --- a/libusb/os/linux_usbfs.h +++ b/libusb/os/linux_usbfs.h @@ -63,6 +63,7 @@ struct usbfs_getdriver { #define USBFS_URB_DISABLE_SPD 1 #define USBFS_URB_ISO_ASAP 2 #define USBFS_URB_QUEUE_BULK 0x10 +#define USBFS_URB_ZERO_PACKET 0x40 enum usbfs_urb_type { USBFS_URB_TYPE_ISO = 0, -- 1.6.0.4