Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935422AbdCMB2f (ORCPT ); Sun, 12 Mar 2017 21:28:35 -0400 Received: from netrider.rowland.org ([192.131.102.5]:60239 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S933621AbdCMB2Y (ORCPT ); Sun, 12 Mar 2017 21:28:24 -0400 Date: Sun, 12 Mar 2017 21:28:22 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Samuel Thibault cc: gregkh@linuxfoundation.org, , , , , , Subject: Re: [PATCHv2] usb-core: Add LINEAR_FRAME_INTR_BINTERVAL USB quirk In-Reply-To: <20170312214856.vt2zx2sqb3x7eti6@var.youpi.perso.aquilenet.fr> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2572 Lines: 70 On Sun, 12 Mar 2017, Samuel Thibault wrote: > Some USB 2.0 devices erroneously report millisecond values in > bInterval. The generic config code manages to catch most of them, > but in some cases it's not completely enough. > > The case at stake here is a USB 2.0 braille device, which wants to > announce 10ms and thus sets bInterval to 10, but with the USB 2.0 > computation that yields to 64ms. It happens that one can type fast > enough to reach this interval and get the device buffers overflown, > leading to problematic latencies. The generic config code does not > catch this case because the 64ms is considered a sane enough value. > > This change thus adds a USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL quirk > to mark devices which actually report milliseconds in bInterval, > and marks Vario Ultra devices as needing it. > > Signed-off-by: Samuel Thibault > > --- a/include/linux/usb/quirks.h > +++ b/include/linux/usb/quirks.h > @@ -50,4 +50,10 @@ > /* device can't handle Link Power Management */ > #define USB_QUIRK_NO_LPM BIT(10) > > +/* > + * Device reports its bInterval as linear frames instead of the > + * USB 2.0 calculation. > + */ > +#define USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL BIT(11) > + > #endif /* __LINUX_USB_QUIRKS_H */ > --- a/drivers/usb/core/config.c > +++ b/drivers/usb/core/config.c > @@ -280,6 +280,16 @@ static int usb_parse_endpoint(struct dev > > /* > * Adjust bInterval for quirked devices. > + */ > + /* > + * This quirk fixes bIntervals reported in ms. > + */ > + if (to_usb_device(ddev)->quirks & > + USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL) { > + n = clamp(fls(d->bInterval) + 3, i, j); > + i = j = n; > + } > + /* > * This quirk fixes bIntervals reported in > * linear microframes. > */ > --- a/drivers/usb/core/quirks.c > +++ b/drivers/usb/core/quirks.c > @@ -170,6 +170,14 @@ static const struct usb_device_id usb_qu > /* M-Systems Flash Disk Pioneers */ > { USB_DEVICE(0x08ec, 0x1000), .driver_info = USB_QUIRK_RESET_RESUME }, > > + /* Baum Vario Ultra */ > + { USB_DEVICE(0x0904, 0x6101), .driver_info = > + USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL }, > + { USB_DEVICE(0x0904, 0x6102), .driver_info = > + USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL }, > + { USB_DEVICE(0x0904, 0x6103), .driver_info = > + USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL }, > + > /* Keytouch QWERTY Panel keyboard */ > { USB_DEVICE(0x0926, 0x3333), .driver_info = > USB_QUIRK_CONFIG_INTF_STRINGS }, Acked-by: Alan Stern