linux-kernel - Re: [PATCH net-next v6 1/6] net: dcb: add new pcp selector to app object

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Message-ID: <87edumvkkx.fsf@nvidia.com>
Date:   Tue, 1 Nov 2022 15:02:39 +0100
From:   Petr Machata <petrm@...dia.com>
To:     Daniel Machon <daniel.machon@...rochip.com>
CC:     <netdev@...r.kernel.org>, <davem@...emloft.net>,
        <petrm@...dia.com>, <maxime.chevallier@...tlin.com>,
        <thomas.petazzoni@...tlin.com>, <edumazet@...gle.com>,
        <kuba@...nel.org>, <pabeni@...hat.com>,
        <lars.povlsen@...rochip.com>, <Steen.Hegelund@...rochip.com>,
        <UNGLinuxDriver@...rochip.com>, <joe@...ches.com>,
        <linux@...linux.org.uk>, <horatiu.vultur@...rochip.com>,
        <Julia.Lawall@...ia.fr>, <vladimir.oltean@....com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH net-next v6 1/6] net: dcb: add new pcp selector to app
 object


Daniel Machon <daniel.machon@...rochip.com> writes:

> Add new PCP selector for the 8021Qaz APP managed object.
>
> As the PCP selector is not part of the 8021Qaz standard, a new non-std
> extension attribute DCB_ATTR_DCB_APP has been introduced. Also two
> helper functions to translate between selector and app attribute type
> has been added. The new selector has been given a value of 255, to
> minimize the risk of future overlap of std- and non-std attributes.
>
> The new DCB_ATTR_DCB_APP is sent alongside the ieee std attribute in the
> app table. This means that the dcb_app struct can now both contain std-
> and non-std app attributes. Currently there is no overlap between the
> selector values of the two attributes.
>
> The purpose of adding the PCP selector, is to be able to offload
> PCP-based queue classification to the 8021Q Priority Code Point table,
> see 6.9.3 of IEEE Std 802.1Q-2018.
>
> PCP and DEI is encoded in the protocol field as 8*dei+pcp, so that a
> mapping of PCP 2 and DEI 1 to priority 3 is encoded as {255, 10, 3}.
>
> Signed-off-by: Daniel Machon <daniel.machon@...rochip.com>

Reviewed-by: Petr Machata <petrm@...dia.com>