linux-kernel - Re: [PATCH] thunderbolt: icm: Remove Apple check for Alpine Ridge

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Message-ID: <20170807070254.GL2369@lahna.fi.intel.com>
Date:   Mon, 7 Aug 2017 10:02:54 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, andreas.noever@...il.com,
        michael.jamet@...el.com, yehezkel.bernat@...el.com
Subject: Re: [PATCH] thunderbolt: icm: Remove Apple check for Alpine Ridge

On Mon, Aug 07, 2017 at 02:50:49PM +0800, Kai-Heng Feng wrote:
> On Mon, Aug 7, 2017 at 12:49 PM, Kai-Heng Feng
> <kai.heng.feng@...onical.com> wrote:
> > In icm_ar_is_supported(), icm->upstream_port will be uninitialized if
> > the hardware is not an Apple one.
> >
> > The uninitialized icm->upstream_port will later be dereferenced in
> > pcie2cio_write(), causes a NULL pointer dereference issue.
> >
> > Commit f67cf491175a ("thunderbolt: Add support for Internal Connection
> > Manager (ICM)") states that all Alpine Ridge will use ICM, so I guess
> > it's safe to remove the Apple check.

Yes, Alpine Ridge uses ICM but on Apple systems we need to additional
steps to get it up and running. That's why the check is there. So no it
cannot be removed.

Is there an actual issue you are trying to solve here?
                                                                                                                                                                                                                     
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > ---
> >  drivers/thunderbolt/icm.c | 7 -------
> >  1 file changed, 7 deletions(-)
> >
> > diff --git a/drivers/thunderbolt/icm.c b/drivers/thunderbolt/icm.c
> > index bdaac1ff00a5..2ab25aac5446 100644
> > --- a/drivers/thunderbolt/icm.c
> > +++ b/drivers/thunderbolt/icm.c
> > @@ -514,13 +514,6 @@ static bool icm_ar_is_supported(struct tb *tb)
> >         struct icm *icm = tb_priv(tb);
> >
> >         /*
> > -        * Starting from Alpine Ridge we can use ICM on Apple machines
> > -        * as well. We just need to reset and re-enable it first.
> > -        */
> > -       if (!is_apple())
> > -               return true;
> > -
> > -       /*

How did you test this?