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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 18 Jun 2019 15:48:32 +0200
Message-ID: <CAK8P3a0sL+nPmduZd=DNSsntq62e+o3upYsWg=iPNwzvgBp+Mg@mail.gmail.com>
Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver
To:     Alex Elder <elder@linaro.org>
Cc:     Johannes Berg <johannes@sipsolutions.net>, abhishek.esse@gmail.com,
        Ben Chan <benchan@google.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        cpratapa@codeaurora.org, David Miller <davem@davemloft.net>,
        Dan Williams <dcbw@redhat.com>,
        DTML <devicetree@vger.kernel.org>,
        Eric Caruso <ejcaruso@google.com>, evgreen@chromium.org,
        Ilias Apalodimas <ilias.apalodimas@linaro.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-arm-msm@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-soc@vger.kernel.org, Networking <netdev@vger.kernel.org>,
        Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
        syadagir@codeaurora.org
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On Tue, Jun 18, 2019 at 3:16 PM Alex Elder <elder@linaro.org> wrote:
> On 6/17/19 6:28 AM, Johannes Berg wrote:
> > On Tue, 2019-06-11 at 13:56 +0200, Arnd Bergmann wrote:
>
> I'm probably missing something, but I think the checksum
> offload could be handled by the IPA driver rather than
> rmnet.  It seems to be an add-on that is completely
> independent of the multiplexing and aggregation capabilities
> that QMAP provides.

My best guess is that it is part of rmnet simply because this can
be done in a generic way for any qmap based back-end, and rmnet
was intended as the abstraction for qmap.

A better implementation of the checksumming might be to split
it out into a library that is in turn used by qmap drivers. Since this
should be transparent to the user interface, it can be moved
there later.

> >>> If true though, then I think this would be the killer argument *in
> >>> favour* of *not* merging this - because that would mean we *don't* have
> >>> to actually keep the rmnet API around for all foreseeable future.
>
> This is because it's a user space API?  If so I now understand
> what you mean.

Yes, I think agreeing on the general user interface is (as usual) the
one thing that has to be done as a prerequisite. I had originally
hoped that by removing the ioctl interface portion of the driver,
this could be avoided, but that was before I had any idea on the
upper layers.

     Arnd