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Date:   Fri, 10 Jun 2022 21:45:06 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Jiaqing Zhao <jiaqing.zhao@linux.intel.com>
Cc:     Samuel Mendoza-Jonas <sam@mendozajonas.com>,
        "David S . Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        openbmc@lists.ozlabs.org
Subject: Re: [PATCH v2 0/6] Configurable VLAN mode for NCSI driver
Message-ID: <20220610214506.74c3f89c@kernel.org>
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        <20220610130903.0386c0d9@kernel.org>
        <3c9fa928-f416-3526-be23-12644d18db3b@linux.intel.com>
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On Sat, 11 Jun 2022 11:25:03 +0800 Jiaqing Zhao wrote:
> > Why is "ncsi,vlan-mode" set via the device tree? Looks like something
> > that can be configured at runtime.   
> 
> Actually this cannot be configured at runtime, the NCSI spec defines no
> command or register to determine which mode is supported by the device.

To be clear I'm not saying that it should be auto-detected and
auto-configured. Just that user space can issue a command to change 
the config.

> If kernel want to enable VLAN on the NCSI device, either "Filtered tagged
> + Untagged" (current default) or "Any tagged + untagged" mode should be
> enabled, but unfortunately both of these two modes are documented to be
> optionally supported in the spec. And in real cases, there are devices
> that only supports one of them, or neither of them. So I added the device
> tree property to configure which mode to use.

But for a given device its driver knows what modes are supported.
Is it not possible to make the VLAN mode passed thru ncsi-netlink?

Better still, can't "Filtered tagged + Untagged" vs "Any tagged +
untagged" be decided based on netdev features being enabled like it
is for normal netdevs?