Re: Regression due to 59cf44575456 ("USB: core: Fix oversight in SuperSpeed initialization")

Alan Stern
2024-04-22T18:03:53Z

On Mon, Apr 22, 2024 at 07:33:21PM +0200, Linux regression tracking (Thorsten Leemhuis) wrote:
> Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
> for once, to make this easily accessible to everyone.
>
> Is anyone still working on fixing below regression? From here it looks
> stalled, but I might have missed something.

I've been waiting to hear back from Oliver or Takashi. A revised patch
taking my comments into account would be welcome; it should be a very
small change (just one or two lines of code).

Alan Stern

> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> --
> Everything you wanna know about Linux kernel regression tracking:
> https://linux-regtracking.leemhuis.info/about/#tldr
> If I did something stupid, please tell me, as explained on that page.
>
> #regzbot poke
>
> On 09.04.24 16:56, Alan Stern wrote:
> > On Tue, Apr 09, 2024 at 03:49:01PM +0200, Oliver Neukum wrote:
> >> Hi,
> >>
> >> with the following device:
> >>
> >> Bus 002 Device 002: ID fb5d:0001 BHYVE HID Tablet
> >> Device Descriptor:
> >> bLength 18
> >> bDescriptorType 1
> >> bcdUSB 3.00
> >> bDeviceClass 0
> >> bDeviceSubClass 0
> >> bDeviceProtocol 0
> >> bMaxPacketSize0 8
> >
> > A USB-3 device, running at SuperSpeed with its bMaxPacketSize0 set to 8
> > instead of 9? Presumably this thing never received a USB certification.
> > Does the packaging use the USB logo?
> >
> >> idVendor 0xfb5d
> >> idProduct 0x0001
> >> bcdDevice 0.00
> >> iManufacturer 1 BHYVE
> >> iProduct 2 HID Tablet
> >> iSerial 3 01
> >> bNumConfigurations 1
> >
> > Why on earth would an HID tablet need to run at SuperSpeed?
> >
> >> Binary Object Store Descriptor:
> >> bLength 5
> >> bDescriptorType 15
> >> wTotalLength 0x000f
> >> bNumDeviceCaps 1
> >> SuperSpeed USB Device Capability:
> >> bLength 10
> >> bDescriptorType 16
> >> bDevCapabilityType 3
> >> bmAttributes 0x00
> >> wSpeedsSupported 0x0008
> >> Device can operate at SuperSpeed (5Gbps)
> >> bFunctionalitySupport 3
> >> Lowest fully-functional device speed is SuperSpeed (5Gbps)
> >> bU1DevExitLat 10 micro seconds
> >> bU2DevExitLat 32 micro seconds
> >
> > A tablet not capable of running at any speed below 5 Gbps?
> >
> >> we are getting a regression on enumeration. It used to work with the
> >> code prior to your patch. Takashi is proposing the attached fixed.
> >> It looks like we are a bit too restrictive and should just try.
> >>
> >> Regards
> >> Oliver
> >
> >> From: Takashi Iwai <tiwai@suse.de>
> >> Subject: [PATCH] USB: hub: Workaround for buggy max packet size with super
> >> speed
> >> Patch-mainline: Not yet, testing
> >> References: bsc#1220569
> >>
> >> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> >>
> >> ---
> >> drivers/usb/core/hub.c | 13 ++++++++++---
> >> 1 file changed, 10 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> >> index e38a4124f610..64193effc456 100644
> >> --- a/drivers/usb/core/hub.c
> >> +++ b/drivers/usb/core/hub.c
> >> @@ -4830,7 +4830,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
> >> const char *driver_name;
> >> bool do_new_scheme;
> >> const bool initial = !dev_descr;
> >> - int maxp0;
> >> + int maxp0, ep0_maxp;
> >> struct usb_device_descriptor *buf, *descr;
> >>
> >> buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO);
> >> @@ -5070,7 +5070,8 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
> >> else
> >> i = 0; /* Invalid */
> >> }
> >> - if (usb_endpoint_maxp(&udev->ep0.desc) == i) {
> >> + ep0_maxp = usb_endpoint_maxp(&udev->ep0.desc);
> >> + if (ep0_maxp == i) {
> >
> > This variable looks like it was left over from earlier testing. It's
> > not really needed.
> >
> >> ; /* Initial ep0 maxpacket guess is right */
> >> } else if ((udev->speed == USB_SPEED_FULL ||
> >> udev->speed == USB_SPEED_HIGH) &&
> >> @@ -5082,9 +5083,15 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
> >> dev_warn(&udev->dev, "Using ep0 maxpacket: %d\n", i);
> >> udev->ep0.desc.wMaxPacketSize = cpu_to_le16(i);
> >> usb_ep0_reinit(udev);
> >> + } else if (udev->speed >= USB_SPEED_SUPER && initial) {
> >> + /* FIXME: should be more restrictive? */
> >> + /* Initial guess is wrong; use the descriptor's value */
> >> + dev_warn(&udev->dev, "Using ep0 maxpacket: %d\n", i);
> >> + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(i);
> >> + usb_ep0_reinit(udev);
> >
> > This could be merged with the previous case fairly easily.
> >
> >> } else {
> >> /* Initial guess is wrong and descriptor's value is invalid */
> >> - dev_err(&udev->dev, "Invalid ep0 maxpacket: %d\n", maxp0);
> >> + dev_err(&udev->dev, "Invalid ep0 maxpacket: %d, expected %d\n", maxp0, ep0_maxp);
> >
> > This also looks like a remnant from earlier testing.
> >
> > Alan Stern
> >
> >> retval = -EMSGSIZE;
> >> goto fail;
> >> }
> >> --
> >> 2.35.3
> >>
> >
>