patch "USB: change bInterval default to 10 ms" added to usb-linus
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This is a note to let you know that I've just added the patch titled
USB: change bInterval default to 10 ms
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
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From
08c5cd37480f59ea39682f4585d92269be6b1424Mon Sep 17 00:00:00 2001
From: Alan Stern <[email protected]>
Date: Fri, 16 Sep 2016 10:24:26 -0400
Subject: USB: change bInterval default to 10 ms
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.
--- drivers/usb/core/config.c | 28 +++++++++++++++++----------- 1 file changed, 17 insertions(+), 11 deletions(-)
drivers/usb/core/config.c +17 -11
@@ -240,8 +240,10 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,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 device *ddev, int cfgno, int inum,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 device *ddev, int cfgno, int inum, }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 device *ddev, int cfgno, int inum, 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 ; } }
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