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[71.195.29.92]) by smtp.googlemail.com with ESMTPSA id x22sm14207341iob.84.2019.06.18.07.00.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Jun 2019 07:00:58 -0700 (PDT) Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver To: Johannes Berg , Arnd Bergmann Cc: abhishek.esse@gmail.com, Ben Chan , Bjorn Andersson , cpratapa@codeaurora.org, David Miller , Dan Williams , DTML , Eric Caruso , evgreen@chromium.org, Ilias Apalodimas , Linux ARM , linux-arm-msm@vger.kernel.org, Linux Kernel Mailing List , linux-soc@vger.kernel.org, Networking , Subash Abhinov Kasiviswanathan , syadagir@codeaurora.org References: <380a6185-7ad1-6be0-060b-e6e5d4126917@linaro.org> <583907409fad854bd3c18be688ec2724ad7a60e9.camel@sipsolutions.net> From: Alex Elder Message-ID: <31c2c94c-c6d3-595b-c138-faa54d0bfc00@linaro.org> Date: Tue, 18 Jun 2019 09:00:57 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <583907409fad854bd3c18be688ec2724ad7a60e9.camel@sipsolutions.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 6/17/19 7:14 AM, Johannes Berg wrote: > On Tue, 2019-06-11 at 13:56 +0200, Arnd Bergmann wrote: > > [...] > > Looking at the flags again, I sort of talked about this in my message a little earlier, but I now see I was partially mistaken. I thought these flags were used in messages but they're real device ("port") configuration flags. >> #define RMNET_FLAGS_INGRESS_DEAGGREGATION (1U << 0) > > This one I'm not sure I understand - seems weird to have such a > fundamental thing as a *configuration* on the channel. Let me use the term "connection" to refer to the single pathway that carries data between the AP and modem. And "channel" to refer to one of several multiplexed data streams carried over that connection. (If there's better terminology, please say so; I just want to be clear in what I'm talking about.) Deaggregation is a connection property, not a channel property. And it looks like that's exactly how it's used in the rmnet driver. The hardware is capable of aggregating QMAP packets arriving on a connection into a single buffer, so this provides a way of requesting it do that. >> #define RMNET_FLAGS_INGRESS_MAP_COMMANDS (1U << 1) > > Similar here? If you have flow control you probably want to use it? I agree with that, though perhaps there are cases where it is pointless, or can't be supported, so one might want to simply *not* implement/advertise the feature. I don't know. >> #define RMNET_FLAGS_INGRESS_MAP_CKSUMV4 (1U << 2) > > This again looks like a hardware specific feature (ipv4 checksum)? Not > sure why this is set by userspace. > >> #define RMNET_FLAGS_EGRESS_MAP_CKSUMV4 (1U << 3) > > This could be set with ethtool instead, I suppose. As I said in my earlier message, I think I concur about this. I think the IPA driver could easily hide the checksum offload capability, and if it can truly be controlled as needed using existing methods there's no need to encumber the WWAN framework with it. -Alex > johannes >