netdev - Re: [PATCH net-next] net/packet: Fix a comment about mac

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Date:   Thu, 17 Sep 2020 10:50:30 +0200
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Xie He <xie.he.0141@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        John Ogness <john.ogness@...utronix.de>,
        Wang Hai <wanghai38@...wei.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH net-next] net/packet: Fix a comment about mac_header

On Wed, Sep 16, 2020 at 8:54 PM Xie He <xie.he.0141@...il.com> wrote:
>
> 1. Change all "dev->hard_header" to "dev->header_ops"
>
> 2. On receiving incoming frames when header_ops == NULL:
>
> The comment only says what is wrong, but doesn't say what is right.
> This patch changes the comment to make it clear what is right.
>
> 3. On transmitting and receiving outgoing frames when header_ops == NULL:
>
> The comment explains that the LL header will be later added by the driver.
>
> However, I think it's better to simply say that the LL header is invisible
> to us. This phrasing is better from a software engineering perspective,
> because this makes it clear that what happens in the driver should be
> hidden from us and we should not care about what happens internally in the
> driver.
>
> 4. On resuming the LL header (for RAW frames) when header_ops == NULL:
>
> The comment says we are "unlikely" to restore the LL header.
>
> However, we should say that we are "unable" to restore it.
> It's not possible (rather than not likely) to restore it, because:
>
> 1) There is no way for us to restore because the LL header internally
> processed by the driver should be invisible to us.
>
> 2) In function packet_rcv and tpacket_rcv, the code only tries to restore
> the LL header when header_ops != NULL.
>
> Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> Signed-off-by: Xie He <xie.he.0141@...il.com>

Acked-by: Willem de Bruijn <willemb@...gle.com>