linux-kernel - Re: [PATCH v27 01/32] xhci: add helper to stop endpoint and wait for completion

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Message-ID: <20240913103237.2f5dc796@foxbook>
Date: Fri, 13 Sep 2024 10:32:37 +0200
From: Michał Pecio <michal.pecio@...il.com>
To: quic_wcheng@...cinc.com, mathias.nyman@...ux.intel.com
Cc: Thinh.Nguyen@...opsys.com, alsa-devel@...a-project.org,
 bgoswami@...cinc.com, broonie@...nel.org, conor+dt@...nel.org,
 corbet@....net, devicetree@...r.kernel.org, dmitry.torokhov@...il.com,
 gregkh@...uxfoundation.org, krzk+dt@...nel.org, lgirdwood@...il.com,
 linux-arm-msm@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-sound@...r.kernel.org, linux-usb@...r.kernel.org,
 mathias.nyman@...el.com, perex@...ex.cz,
 pierre-louis.bossart@...ux.intel.com, robh@...nel.org,
 srinivas.kandagatla@...aro.org, tiwai@...e.com
Subject: Re: [PATCH v27 01/32] xhci: add helper to stop endpoint and wait
 for completion

Hi,

> Expose xhci_stop_endpoint_sync() which is a synchronous variant of
> xhci_queue_stop_endpoint().  This is useful for client drivers that are
> using the secondary interrupters, and need to stop/clean up the current
> session.  The stop endpoint command handler will also take care of
> cleaning up the ring.

I'm not entirely sure what you meant by "cleaning up the ring" (maybe a
comment would be in order?), but I see nothing being done here after the
command completes and FYI xhci-ring.c will not run the default handler if
the command is queued with a completion, like here.

At least that's the case for certain command types and there is probably
a story behind each of them. I know that xhci_stop_device() queues a
Stop EP with completion (and also a few without(?)). Maybe it's a bug...

Regards,
Michal