linux-kernel - Re: [PATCH] usb: xhci: Don't unchain link TRBs on quirky HCs

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Message-ID: <20251114123232.0b96bfa5.michal.pecio@gmail.com>
Date: Fri, 14 Nov 2025 12:32:32 +0100
From: Michal Pecio <michal.pecio@...il.com>
To: Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc: Mathias Nyman <mathias.nyman@...el.com>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: xhci: Don't unchain link TRBs on quirky HCs

On Tue, 11 Nov 2025 18:19:38 +0200, Mathias Nyman wrote:
> On 11/7/25 12:08, Michal Pecio wrote:
> > +static void td_to_noop(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
> > +			struct xhci_td *td, bool flip_cycle)  
> 
> we could avoid passing xhci pointer to td_to_noop() and just grab it from
> the xhci_virt_ep structure instead. i.e. ep->xhci

I can do a v2 if you want.

But OTOH, I didn't expect such pointer to exist (though I'm sure I must
have seen it many times) because it doesn't seem strictly necessary.

Maybe do the reverse and get rid of ep->xhci, or stop adding new users
and clean up existing ones along the way?

Main users are invalidate_cancelled_tds()/giveback_invalidated_tds(),
their callers all have xhci and could easily supply it to them. And we
even discussed removing the latter completely, but I got sidetracked by
issues with URB_ZERO_PACKET.

Another user is xhci_handle_cmd_set_deq() which already has xhci.
I have a compile-tested patch which removes it completely right now,
it took five minutes and zero mental effort to prepare.

Regards,
Michal