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From:   Sai Krishna Gajula <saikrishnag@marvell.com>
To:     Dan Carpenter <dan.carpenter@linaro.org>
CC:     "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
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        Sunil Kovvuri Goutham <sgoutham@marvell.com>,
        "maciej.fijalkowski@intel.com" <maciej.fijalkowski@intel.com>,
        Naveen Mamindlapalli <naveenm@marvell.com>
Subject: Re: [net PATCH v2] octeontx2-af: Move validation of ptp pointer
 before its usage
Thread-Topic: [net PATCH v2] octeontx2-af: Move validation of ptp pointer
 before its usage
Thread-Index: AQHZqxJweVNRvtU2DkO6MScNy+K7wA==
Date:   Fri, 30 Jun 2023 05:19:27 +0000
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> -----Original Message-----
> From: Dan Carpenter <dan.carpenter@linaro.org>
> Sent: Friday, June 23, 2023 5:14 PM
> To: Sai Krishna Gajula <saikrishnag@marvell.com>
> Cc: davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> pabeni@redhat.com; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; Sunil Kovvuri Goutham <sgoutham@marvell.com>;
> maciej.fijalkowski@intel.com; Naveen Mamindlapalli
> <naveenm@marvell.com>
> Subject: Re: [net PATCH v2] octeontx2-af: Move validation of ptp
> pointer before its usage
>=20
> On Fri, Jun 23, 2023 at 11:28:19AM +0000, Sai Krishna Gajula wrote:
> > > This probe function is super weird how it returns success on the fail=
ure
> path.
> > > One concern, I had initially was that if anything returns
> > > -EPROBE_DEFER then we cannot recover.  That's not possible in the
> > > current code, but it makes me itch...  But here is a different crash.
> > >
> >
> > In few circumstances, the PTP device is probed before the AF device in
> > the driver. In such instance, -EPROBE_DEFER is used.
> > -- EDEFER_PROBE is useful when probe order changes. Ex: AF driver probe=
s
> before PTP.
> >
>=20
> You're describing how -EPROBE_DEFER is *supposed* to work.  But that's no=
t
> what this driver does.
>=20
> If the AF driver is probed before the PTP driver then ptp_probe() should
> return -EPROBE_DEFER and that would allow the kernel to automatically ret=
ry
> ptp_probe() later.  But instead of that, ptp_probe() returns success.  So=
 I
> guess the user would have to manually rmmod it and insmod it again?  So,
> what I'm saying I don't understand why we can't do this in the normal way=
.
>=20
> The other thing I'm saying is that the weird return success on error stuf=
f
> hasn't been tested or we would have discovered the crash through testing.
>=20
> regards,
> dan carpenter

As suggested, we will return error in ptp_probe in case of any failure cond=
itions. In this case AF driver continues without PTP support.
When the AF driver is probed before PTP driver , we will defer the AF probe=
. Hope these changes are inline with your view.
I will send a v3 patch with these changes.=20

Regards,
Sai