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

Alan Stern
2024-04-23T19:29:34Z

On Mon, Apr 22, 2024 at 09:24:24PM +0200, Takashi Iwai wrote:
> On Mon, 22 Apr 2024 20:03:46 +0200,
> Alan Stern wrote:
> >
> > 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).
>
> As posted in another mail, it's a virtualized environment.
> Details are found in the original bug report
> https://bugzilla.suse.com/show_bug.cgi?id=1220569

Hmmm. If this is a virtualized device, isn't the best solution to fix the
emulation code for the device so that it presents a valid descriptor?

> About the patch change: I appreciate if you cook it rather by
> yourself since I'm not 100% sure what you suggested. I can
> provide the reporter a test kernel with the patch for confirmation, of
> course.

Here's a condensed version of the patch you wrote. But I would prefer not
to add this to the kernel if the problem can be fixed somewhere else.

Alan Stern

Index: usb-devel/drivers/usb/core/hub.c
===================================================================
--- usb-devel.orig/drivers/usb/core/hub.c
+++ usb-devel/drivers/usb/core/hub.c
@@ -5110,9 +5110,10 @@ hub_port_init(struct usb_hub *hub, struc
}
if (usb_endpoint_maxp(&udev->ep0.desc) == i) {
; /* Initial ep0 maxpacket guess is right */
- } else if ((udev->speed == USB_SPEED_FULL ||
+ } else if (((udev->speed == USB_SPEED_FULL ||
udev->speed == USB_SPEED_HIGH) &&
- (i == 8 || i == 16 || i == 32 || i == 64)) {
+ (i == 8 || i == 16 || i == 32 || i == 64)) ||
+ (udev->speed >= USB_SPEED_SUPER && i > 0)) {
/* Initial guess is wrong; use the descriptor's value */
if (udev->speed == USB_SPEED_FULL)
dev_dbg(&udev->dev, "ep0 maxpacket = %d\n", i);