On Sat, 26 Jul 2014, James P Michels III wrote:
> This patch adds a usb quirk to support devices with bInterval values
> expressed as microframes. The quirk causes the parse endpoint function
> to modify the reported bInterval to a standards conforming value.
You need to mention that the quirk applies to interrupt endpoints, not
isochronous endpoints.
> There is currently code in the endpoint parser that checks for
> bIntervals that are outside of the valid range (1-16 for USB 2+).
1-16 is the valid range for high speed and SuperSpeed. USB-2 also
includes low speed and full speed, for which the valid range is 1-255.
See Table 9-13 in the USB-2.0 spec.
> In this case, the code assumes the bInterval is being reported in
> 1ms frames. As well, the correction is only applied if the original
> bInterval value is out of the 1-16 range.
>
> With this quirk applied to the device, the bInterval will be
> accurately adjusted from microframes to an exponent.
>
> Signed-off-by: James P Michels III <james.p.michels@xxxxxxxxx>
> ---
> drivers/usb/core/config.c | 9 +++++++++
> drivers/usb/core/quirks.c | 4 ++++
> include/linux/usb/quirks.h | 9 +++++++++
> 3 files changed, 22 insertions(+)
>
> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> index 1ab4df1..191ce69 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -199,6 +199,15 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
> if (n == 0)
> n = 9; /* 32 ms = 2^(9-1) uframes */
> j = 16;
> +
> + /* Adjust bInterval for quirked devices.
> + * This quirk fixes bIntervals reported in
> + * linear microframes. */
> + if (to_usb_device(ddev)->quirks &
> + USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL) {
> + n = clamp(fls(d->bInterval), i, j);
> + i = j = n;
> + }
The closing brace is in the wrong column. Also, people are likely to
complain about the style of the multi-line comment. Although it's the
same as the rest of the source file, nowadays we prefer all new
comments to have the form:
/*
* Blah blah blah
* blah blah blah
*/
> --- a/include/linux/usb/quirks.h
> +++ b/include/linux/usb/quirks.h
> @@ -30,4 +30,13 @@
> descriptor */
> #define USB_QUIRK_DELAY_INIT 0x00000040
>
> +/* The USB 2.0 and USB 3.0 spec require the interval in microframes
> + (1 microframe = 125 microseconds) to be calculated as
> + interval = 2 ^ (bInterval -1).
Spacing around the minus sign is wrong. And again, this applies only
to high-speed and SuperSpeed devices. The quirk itself applies only to
interrupt endpoints.
> +
> + Devices with this quirk report their bInterval as the result of
> + this calculation instead of the exponent variable used in the
> + calculation */
Wrong style in this multi-line comment.
> +#define USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL 0x00000080
> +
> #endif /* __LINUX_USB_QUIRKS_H */
Aside from those relatively minor issues, this is okay.
Alan Stern
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