From micah@vmware.com Fri May 19 11:20:23 2006 Message-ID: <446E0C5B.3080204@vmware.com> Date: Fri, 19 May 2006 11:20:11 -0700 From: Micah Dowty To: linux-usb-devel@lists.sourceforge.net Cc: Greg KH Subject: USB: Remove 4088-byte limit on usbfs control URBs This patch removes the artificial 4088-byte limit that usbfs currently places on Control transfers. The USB spec does not specify a strict limit on the size of an entire control transfer. It does, however, state that the data stage "follows the same protocol rules as bulk transfers." (USB 2, 8.5.3) The level of support for large control transfers in real host controllers varies, but it's important to support at least 4K transfers. Windows enforces a maximum control transfer size of 4K, so there exists some hardware that requires a full 4096 byte data stage. Without this patch, we fall short of that by 8 bytes on architectures with a 4K page size, and it becomes impossible to support such hardware with a user-space driver. Since any limit placed on control transfers by usbfs would be arbitrary, this patch replaces the PAGE_SIZE limit with the same arbitrary limit used by bulk transfers. Signed-off-by: Micah Dowty Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/devio.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- gregkh-2.6.orig/drivers/usb/core/devio.c +++ gregkh-2.6/drivers/usb/core/devio.c @@ -923,8 +923,8 @@ static int proc_do_submiturb(struct dev_ if ((ep->desc.bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) != USB_ENDPOINT_XFER_CONTROL) return -EINVAL; - /* min 8 byte setup packet, max arbitrary */ - if (uurb->buffer_length < 8 || uurb->buffer_length > PAGE_SIZE) + /* min 8 byte setup packet, max 8 byte setup plus an arbitrary data stage */ + if (uurb->buffer_length < 8 || uurb->buffer_length > (8 + MAX_USBFS_BUFFER_SIZE)) return -EINVAL; if (!(dr = kmalloc(sizeof(struct usb_ctrlrequest), GFP_KERNEL))) return -ENOMEM;