linux-kernel - Re: [PATCH v2] usb: hcd: Add a usb_device argument to hc_driver.endpoint

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Message-ID: <20250416082958.20c34504@foxbook>
Date: Wed, 16 Apr 2025 08:29:58 +0200
From: Michał Pecio <michal.pecio@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Mathias Nyman <mathias.nyman@...el.com>, Minas Harutyunyan
 <hminas@...opsys.com>, Linus Walleij <linus.walleij@...aro.org>, Alan Stern
 <stern@...land.harvard.edu>, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] usb: hcd: Add a usb_device argument to
 hc_driver.endpoint_reset()

On Tue, 15 Apr 2025 14:26:26 +0200, Greg Kroah-Hartman wrote:
> > This fixes a 6.15-rc1 regression reported by Paul, which I was able
> > to reproduce, where xhci_hcd doesn't handle endpoint_reset() after
> > endpoint_disable() not followed by add_endpoint(). If a configured
> > device is reset, stalling endpoints start to get stuck permanently.
>
> As this fixes a bug, can you add a Fixes: tag with the needed
> information?

Hi Greg,

Sorry for bothering you, the real bug is that I forgot to carry over
the RFC tag from v1.

The 6.15 regression is currently solved by reverts Mathias sent you.

The underlying bug is much older, I would have to research where it
went wrong exactly. It was very obscure; a class driver would need to:

1. call usb_set_interface(), usb_reset_device() or something like that
2. submit some URBs to make the toggle/sequence state non-zero
3. call usb_clear_halt() on a not yet halted endpoint

Then the host endpoint wouldn't be reset, but the device would.

I know of drivers which do 1 and 2 or even 2 and 3, but I have not
yet encountered a driver doing all three in this order.

Regards,
Michal