Re: [RFC PATCH 1/2] xhci: prevent automatic endpoint restart after stall or error

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On Thu, Apr 02, 2026, Mathias Nyman wrote:
> On 4/2/26 01:08, Thinh Nguyen wrote:
> > On Mon, Mar 30, 2026, Mathias Nyman wrote:
> > > 
> > > > 
> > > > On a separate note, will you plan to implement the clear-halt for EPROTO
> > > > in xhci?
> > > 
> > > I don't think this should be part of xhci driver. Decision to send control requests
> > > to the device should be done by core or class drivers.
> > > 
> > 
> > This not like STALL where it's standardized for the core or class driver
> > to know how to handle. The programming sequence for the errors that
> > resulted in EPROTO from xhci is specific to xhci. That is, the xhci
> > reset endpoint command will reset the bulk sequence, it's specific to
> > xhci. The xhci spec recommends to send a clear-halt for this scenario,
> > not the USB spec or any other class specific spec. So we should not
> > delegate this to the core or class driver to handle.
> > 
> USB 2 Specification does mention handling halt conditions due to  transmission
> erros _OR_ STALL handshake with clearing halt and resetting both host and device
> endpoint toggle.
> 
> See USB 2
> 
> 5.7.5 Interrupt Transfer Data Sequences
> 
> "If a halt condition is detected on an interrupt pipe due to transmission errors or
>  a STALL handshake being returned from the endpoint, all pending IRPs are retired.
>  Removal of the halt condition is achieved via software intervention through a
>  separate control pipe. This recovery will reset the data toggle bit to DATA0 for
>  the endpoint on both the host and the device"
> 
> 5.8.5 Bulk Transfer Data Sequences
> 
> "If a halt condition is detected on a bulk pipe due to transmission errors or a
>  STALL handshake being returned from the endpoint, all pending IRPs are retired.
>  Removal of the halt condition is achieved via software intervention through a
>  separate control pipe. This recovery will reset the data toggle bit to DATA0
>  for the endpoint on both the host and the device"
> 

Ah~ I stand corrected. My memory served me wrong. Thanks for pointing
this out.

BR,
Thinh