Em Fri, 16 Sep 2016 10:24:26 -0400 (EDT)
Alan Stern <st...@rowland.harvard.edu> escreveu:
> Some full-speed mceusb infrared transceivers contain invalid endpoint
> descriptors for their interrupt endpoints, with bInterval set to 0.
> In the past they have worked out okay with the mceusb driver, because
> the driver sets the bInterval field in the descriptor to 1,
> overwriting whatever value may have been there before. However, this
> approach was never sanctioned by the USB core, and in fact it does not
> work with xHCI controllers, because they use the bInterval value that
> was present when the configuration was installed.
>
> Currently usbcore uses 32 ms as the default interval if the value in
> the endpoint descriptor is invalid. It turns out that these IR
> transceivers don't work properly unless the interval is set to 10 ms
> or below. To work around this mceusb problem, this patch changes the
> endpoint-descriptor parsing routine, making the default interval value
> be 10 ms rather than 32 ms.
>
> Signed-off-by: Alan Stern <st...@rowland.harvard.edu>
> Tested-by: Wade Berrier <wberr...@gmail.com>
> CC: <sta...@vger.kernel.org>
Acked-by: Mauro Carvalho Chehab <m.che...@s-opensource.com>
>
> ---
>
>
> [as1812]
>
>
> drivers/usb/core/config.c | 28 +++++++++++++++++-----------
> 1 file changed, 17 insertions(+), 11 deletions(-)
>
> Index: usb-4.x/drivers/usb/core/config.c
> ===================================================================
> --- usb-4.x.orig/drivers/usb/core/config.c
> +++ usb-4.x/drivers/usb/core/config.c
> @@ -240,8 +240,10 @@ static int usb_parse_endpoint(struct dev
> memcpy(&endpoint->desc, d, n);
> INIT_LIST_HEAD(&endpoint->urb_list);
>
> - /* Fix up bInterval values outside the legal range. Use 32 ms if no
> - * proper value can be guessed. */
> + /*
> + * Fix up bInterval values outside the legal range.
> + * Use 10 or 8 ms if no proper value can be guessed.
> + */
> i = 0; /* i = min, j = max, n = default */
> j = 255;
> if (usb_endpoint_xfer_int(d)) {
> @@ -250,13 +252,15 @@ static int usb_parse_endpoint(struct dev
> case USB_SPEED_SUPER_PLUS:
> case USB_SPEED_SUPER:
> case USB_SPEED_HIGH:
> - /* Many device manufacturers are using full-speed
> + /*
> + * Many device manufacturers are using full-speed
> * bInterval values in high-speed interrupt endpoint
> - * descriptors. Try to fix those and fall back to a
> - * 32 ms default value otherwise. */
> + * descriptors. Try to fix those and fall back to an
> + * 8-ms default value otherwise.
> + */
> n = fls(d->bInterval*8);
> if (n == 0)
> - n = 9; /* 32 ms = 2^(9-1) uframes */
> + n = 7; /* 8 ms = 2^(7-1) uframes */
> j = 16;
>
> /*
> @@ -271,10 +275,12 @@ static int usb_parse_endpoint(struct dev
> }
> break;
> default: /* USB_SPEED_FULL or _LOW */
> - /* For low-speed, 10 ms is the official minimum.
> + /*
> + * For low-speed, 10 ms is the official minimum.
> * But some "overclocked" devices might want faster
> - * polling so we'll allow it. */
> - n = 32;
> + * polling so we'll allow it.
> + */
> + n = 10;
> break;
> }
> } else if (usb_endpoint_xfer_isoc(d)) {
> @@ -282,10 +288,10 @@ static int usb_parse_endpoint(struct dev
> j = 16;
> switch (to_usb_device(ddev)->speed) {
> case USB_SPEED_HIGH:
> - n = 9; /* 32 ms = 2^(9-1) uframes */
> + n = 7; /* 8 ms = 2^(7-1) uframes */
> break;
> default: /* USB_SPEED_FULL */
> - n = 6; /* 32 ms = 2^(6-1) frames */
> + n = 4; /* 8 ms = 2^(4-1) frames */
> break;
> }
> }
>
Thanks,
Mauro
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