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 <samuel.thibault@xxxxxxxxxxxx>
>
> --- 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 <stern@xxxxxxxxxxxxxxxxxxx>
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