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From:   Ray Chi <raychi@google.com>
Date:   Mon, 22 Aug 2022 23:42:11 +0800
Message-ID: <CAPBYUsA0LAYUBtXRuGwo=neLjWyojRUU91vnRE=k6rcimgSVbA@mail.gmail.com>
Subject: Re: [PATCH 2/2] usb: xhci: add check_init_status hook support
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     mathias.nyman@intel.com, stern@rowland.harvard.edu,
        Badhri Jagan Sridharan <badhri@google.com>,
        Albert Wang <albertccwang@google.com>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
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On Tue, Aug 16, 2022 at 4:57 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Aug 16, 2022 at 04:38:54PM +0800, Ray Chi wrote:
> > In general, xHCI didn't do anything for port initialization. However,
> > there are some requirement or limitation on various platforms, so
> > vendors need to do some error handlings if the device connected to a
> > broken USB accessory.
> >
> > This patch also add the hook to xhci_driver_overrides so that vendors
> > can add their specific protection easily if needed.
> >
> > Signed-off-by: Ray Chi <raychi@google.com>
> > ---
> >  drivers/usb/host/xhci.c | 17 +++++++++++++++++
> >  drivers/usb/host/xhci.h |  1 +
> >  2 files changed, 18 insertions(+)
> >
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index 65858f607437..f237af9d6e2e 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -4358,6 +4358,20 @@ static int xhci_enable_device(struct usb_hcd *hcd, struct usb_device *udev)
> >       return xhci_setup_device(hcd, udev, SETUP_CONTEXT_ONLY);
> >  }
> >
> > +/*
> > + * The function could get the status of port initialization.
> > + */
> > +static int xhci_check_init_status(struct usb_hcd *hcd, struct usb_device *udev, int r)
> > +{
> > +     /*
> > +      * In general, this function is not necessory. Some platforms may
> > +      * need doing error handling when the port initialization takes a
> > +      * long time to do. The device can use the override callback to
> > +      * do specific handlings.
> > +      */
> > +     return 0;
> > +}
>
> For obvious technical and legal reasons, we are not allowed to add
> "hooks" to the kernel where there are no in-kernel users.  Nor would you
> want us to do so.
>

Agree on this. I am trying another way to achieve the same goal.

> So I really do not understand this patch series at all.
>
> What driver wants to do odd things here?  What needs to happen that the
> in-tree drivers are not doing properly?  Why not get the needed fixes in
> the in-kernel drivers instead of trying to add random hooks that some
> out-of-tree code would use instead.
>
> confused,
>
> greg k-h

I will prepare a new commit to do it.

Thanks,
Ray