Commit caa9ef67 authored by David Brownell's avatar David Brownell Committed by Greg Kroah-Hartman
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USB: ehci tolerates some buggy devices

This teaches EHCI how to to work around bugs in certain high speed
devices, by accomodating "bulk" packets that exceed the 512 byte
constant value required by the USB 2.0 specification.  (Have a
look at section 5.8.3, paragraphs 1 and 3.)

It also makes the descriptor parsing code warn when it encounters
such bugs.  (We've had reports of maybe two or three such devices,
all pretty recent.)

Such devices are nonconformant.  The proper fix is have the vendors
of those devices do the simple, obvious, and correct thing ... which
will let them be used with USB hosts that don't have workarounds for
this particular vendor bug.  But unless/until they do, we can at least
have one of the high speed HCDs work with such buggy devices.
Signed-off-by: default avatarDavid Brownell <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent e01e7fe3
......@@ -145,6 +145,23 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
endpoint->desc.wMaxPacketSize = cpu_to_le16(8);
* Some buggy high speed devices have bulk endpoints using
* maxpacket sizes other than 512. High speed HCDs may not
* be able to handle that particular bug, so let's warn...
if (to_usb_device(ddev)->speed == USB_SPEED_HIGH
&& usb_endpoint_xfer_bulk(d)) {
unsigned maxp;
maxp = le16_to_cpu(endpoint->desc.wMaxPacketSize) & 0x07ff;
if (maxp != 512)
dev_warn(ddev, "config %d interface %d altsetting %d "
"bulk endpoint 0x%X has invalid maxpacket %d\n",
cfgno, inum, asnum, d->bEndpointAddress,
/* Skip over any Class Specific or Vendor Specific descriptors;
* find the next endpoint or interface descriptor */
endpoint->extra = buffer;
......@@ -657,6 +657,14 @@ qh_make (
type = usb_pipetype (urb->pipe);
maxp = usb_maxpacket (urb->dev, urb->pipe, !is_input);
/* 1024 byte maxpacket is a hardware ceiling. High bandwidth
* acts like up to 3KB, but is built from smaller packets.
if (max_packet(maxp) > 1024) {
ehci_dbg(ehci, "bogus qh maxpacket %d\n", max_packet(maxp));
goto done;
/* Compute interrupt scheduling parameters just once, and save.
* - allowing for high bandwidth, how many nsec/uframe are used?
* - split transactions need a second CSPLIT uframe; same question
......@@ -757,7 +765,13 @@ qh_make (
info2 |= (EHCI_TUNE_MULT_HS << 30);
} else if (type == PIPE_BULK) {
info1 |= (EHCI_TUNE_RL_HS << 28);
info1 |= 512 << 16; /* usb2 fixed maxpacket */
/* The USB spec says that high speed bulk endpoints
* always use 512 byte maxpacket. But some device
* vendors decided to ignore that, and MSFT is happy
* to help them do so. So now people expect to use
* such nonconformant devices with Linux too; sigh.
info1 |= max_packet(maxp) << 16;
info2 |= (EHCI_TUNE_MULT_HS << 30);
} else { /* PIPE_INTERRUPT */
info1 |= max_packet (maxp) << 16;
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