linux-kernel - Re: [PATCHv2] usb-core: Add LINEAR_FRAME_INTR

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Message-ID: <Pine.LNX.4.44L0.1703122127480.30930-100000@netrider.rowland.org>
Date:   Sun, 12 Mar 2017 21:28:22 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Samuel Thibault <samuel.thibault@...-lyon.org>
cc:     gregkh@...uxfoundation.org, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <dave@...lke.cc>,
        <kevin.derome@...tech.eu>, <clause.andreabush@...il.com>,
        <mengualjeanphi@...e.fr>
Subject: Re: [PATCHv2] usb-core: Add LINEAR_FRAME_INTR_BINTERVAL USB quirk

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@...-lyon.org>
> 
> --- 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@...land.harvard.edu>