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

[Takashi Iwai <tiwai@suse.de>]

On Tue, 09 Apr 2024 16:56:53 +0200,
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?

IIUC from the report, this is a virtualization environment, no real
device:
  https://bhyve.npulse.net/


Takashi

> >   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
> > 
>