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Date:   Tue, 4 Oct 2022 12:51:47 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Petr Machata <petrm@nvidia.com>
Cc:     Daniel Machon <daniel.machon@microchip.com>,
        <netdev@vger.kernel.org>, <davem@davemloft.net>,
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        <UNGLinuxDriver@microchip.com>, <joe@perches.com>,
        <linux@armlinux.org.uk>, <horatiu.vultur@microchip.com>,
        <Julia.Lawall@inria.fr>, <vladimir.oltean@nxp.com>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH net-next v2 1/6] net: dcb: add new pcp selector to app
 object
Message-ID: <20221004125147.7f76d409@kernel.org>
In-Reply-To: <87v8ozx3hb.fsf@nvidia.com>
References: <20220929185207.2183473-1-daniel.machon@microchip.com>
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        <87leq1uiyc.fsf@nvidia.com>
        <20220930175452.1937dadd@kernel.org>
        <87pmf9xrrd.fsf@nvidia.com>
        <20221003092522.6aaa6d55@kernel.org>
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        <87v8ozx3hb.fsf@nvidia.com>
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On Tue, 4 Oct 2022 12:52:35 +0200 Petr Machata wrote:
> > The question is whether it's better to do it anyway. My opinion is that
> > if a userspace decides to make assumptions about the contents of a TLV,
> > and neglects to validate the actual TLV type, it's on them, and I'm not
> > obligated to keep them working. We know about this case, but really any
> > attribute addition at all could potentially trip some userspace if they
> > expected something else at this offset.  
> 
> And re the flag: I think struct dcbmsg.dcb_pad was meant to be the place
> to keep flags when the need arises, but it is not validated anywhere, so
> we cannot use it. It could be a new command, but I'm not a fan. So if we
> need to discriminate userspaces, I think it should be a new attribute.

All good points. I'm fine with not gating the attributes if that's your
preference. Your call.