From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750912AbVJNWGk (ORCPT ); Fri, 14 Oct 2005 18:06:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750935AbVJNWGk (ORCPT ); Fri, 14 Oct 2005 18:06:40 -0400 Received: from lana.hrz.tu-chemnitz.de ([134.109.132.3]:50667 "EHLO lana.hrz.tu-chemnitz.de") by vger.kernel.org with ESMTP id S1750911AbVJNWGj (ORCPT ); Fri, 14 Oct 2005 18:06:39 -0400 X-From-Line: nobody Fri Oct 14 19:57:45 2005 To: Greg KH Cc: linux-kernel@vger.kernel.org, stable@kernel.org, Chris Wright , kernel-stuff@comcast.net (Parag Warudkar) Subject: [PATCH] Re: bug in handling of highspeed usb HID devices References: <20051013224839.GA3583@kroah.com> From: Christian Krause Date: Fri, 14 Oct 2005 19:57:45 +0200 User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Jumbo Shrimp, linux) Content-Type: text/plain; charset=us-ascii Message-ID: MIME-Version: 1.0 X-Spam-Score: 0.0 (/) X-Spam-Report: --- Start der SpamAssassin 3.1.0 Textanalyse (0.0 Punkte) Fragen an/questions to: Postmaster TU Chemnitz --- Ende der SpamAssassin Textanalyse X-Scan-Signature: ce20b7edf4650e69c84e96fedf5678d6 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, On Thu, 13 Oct 2005 15:48:39 -0700, Greg KH wrote: > On Wed, Oct 12, 2005 at 09:55:32PM +0200, Christian Krause wrote: >> Here is a small patch which solves the whole problem: > The patch is at the wrong level, and has spaces instead of tabs. > And no "signed-off-by" line :( > Take a look at Documentation/SubmittingPatches for how to create a patch > that I can apply and forward on. Ok, next try with Signed-off-by above the patch. Please apologize the spam. ;-) During the development of an USB device I found a bug in the handling of Highspeed HID devices in the kernel. What happened? Highspeed HID devices are correctly recognized and enumerated by the kernel. But even if usbhid kernel module is loaded, no HID reports are received by the kernel. The output of the hardware USB analyzer told me that the host doesn't even poll for interrupt IN transfers (even the "interrupt in" USB transfer are polled by the host). After some debugging in hid-core.c I've found the reason. In case of a highspeed device, the endpoint interval is re-calculated in driver/usb/input/hid-core.c: line 1669: /* handle potential highspeed HID correctly */ interval = endpoint->bInterval; if (dev->speed == USB_SPEED_HIGH) interval = 1 << (interval - 1); Basically this calculation is correct (refer to USB 2.0 spec, 9.6.6). This new calculated value of "interval" is used as input for usb_fill_int_urb: line 1685: usb_fill_int_urb(hid->urbin, dev, pipe, hid->inbuf, 0, hid_irq_in, hid, interval); Unfortunately the same calculation as above is done a second time in usb_fill_int_urb in the file include/linux/usb.h: line 933: if (dev->speed == USB_SPEED_HIGH) urb->interval = 1 << (interval - 1); else urb->interval = interval; This means, that if the endpoint descriptor (of a high speed device) specifies e.g. bInterval = 7, the urb->interval gets the value: hid-core.c: interval = 1 << (7-1) = 0x40 = 64 urb->interval = 1 << (interval -1) = 1 << (63) = integer overflow Because of this the value of urb->interval is sometimes negative and is rejected in core/urb.c: line 353: /* too small? */ if (urb->interval <= 0) return -EINVAL; The conclusion is, that the recalculaton of the interval (which is necessary for highspeed) should not be made twice, because this is simply wrong. ;-) Re-calculation in usb_fill_int_urb makes more sense, because it is the most general approach. So it would make sense to remove it from hid-core.c. Because in hid-core.c the interval variable is only used for calling usb_fill_int_urb, it is no problem to remove the highspeed re-calculation in this file. Signed-off-by: Christian Krause --------------------------------snip------------------------ --- linux-2.6.13.4/drivers/usb/input/hid-core.c.old 2005-10-12 21:29:29.000000000 +0200 +++ linux-2.6.13.4/drivers/usb/input/hid-core.c 2005-10-12 21:31:02.000000000 +0200 @@ -1667,11 +1667,6 @@ static struct hid_device *usb_hid_config if ((endpoint->bmAttributes & 3) != 3) /* Not an interrupt endpoint */ continue; - /* handle potential highspeed HID correctly */ - interval = endpoint->bInterval; - if (dev->speed == USB_SPEED_HIGH) - interval = 1 << (interval - 1); - /* Change the polling interval of mice. */ if (hid->collection->usage == HID_GD_MOUSE && hid_mousepoll_interval > 0) interval = hid_mousepoll_interval; --------------------------------snip------------------------ Best regards, Christian