netdev - Re: [PATCH net-next v2 2/5] lan743x: sync only the received area of an rx ring buffer

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Date:   Fri, 12 Feb 2021 17:38:47 -0500
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     Bryan Whitehead <Bryan.Whitehead@...rochip.com>
Cc:     Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Alexey Denisov <rtgbnm@...il.com>,
        Sergej Bauer <sbauer@...ckbox.su>,
        Tim Harvey <tharvey@...eworks.com>,
        Anders Rønningen <anders@...ningen.priv.no>,
        Hillf Danton <hdanton@...a.com>,
        Christoph Hellwig <hch@....de>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2 2/5] lan743x: sync only the received area of
 an rx ring buffer

Hi Bryan,

On Fri, Feb 12, 2021 at 3:45 PM <Bryan.Whitehead@...rochip.com> wrote:
>
> According to the document I have, FRAME_LENGTH is only valid when LS bit is set, and reserved otherwise.
> Therefore, I'm not sure you can rely on it being zero when LS is not set, even if your experiments say it is.
> Future chip revisions might use those bits differently.

That's good to know. I didn't find any documentation related to
multi-buffer frames, so I had to go with what I saw the chip do
experimentally. It's great that you were able to double-check against
the official docs.

>
> Can you change this so the LS bit is checked.
>         If set you can use the smaller of FRAME_LENGTH or buffer length.
>         If clear you can just use buffer length.

Will do. Are you planning to hold off your tests until v3? It
shouldn't take too long.