From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Berg Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver Date: Tue, 18 Jun 2019 23:02:18 +0200 Message-ID: <6e7f0fb2f85d5062a9e23d37c47d311e10aa4624.camel@sipsolutions.net> References: <380a6185-7ad1-6be0-060b-e6e5d4126917@linaro.org> <066e9b39f937586f0f922abf801351553ec2ba1d.camel@sipsolutions.net> <613cdfde488eb23d7207c7ba6258662702d04840.camel@sipsolutions.net> (sfid-20190618_225543_624686_3B7D51E7) Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: (sfid-20190618_225543_624686_3B7D51E7) List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Arnd Bergmann Cc: DTML , syadagir@codeaurora.org, Eric Caruso , Dan Williams , linux-arm-msm@vger.kernel.org, abhishek.esse@gmail.com, Linux Kernel Mailing List , evgreen@chromium.org, Bjorn Andersson , Ilias Apalodimas , Linux ARM , Alex Elder , Subash Abhinov Kasiviswanathan , Networking , linux-soc@vger.kernel.org, David Miller , cpratapa@codeaurora.org, Ben Chan List-Id: devicetree@vger.kernel.org On Tue, 2019-06-18 at 22:55 +0200, Arnd Bergmann wrote: > On Tue, Jun 18, 2019 at 10:36 PM Johannes Berg > wrote: > > > > On Tue, 2019-06-18 at 21:59 +0200, Arnd Bergmann wrote: > > > > > > From my understanding, the ioctl interface would create the lower > > > netdev after talking to the firmware, and then user space would use > > > the rmnet interface to create a matching upper-level device for that. > > > This is an artifact of the strong separation of ipa and rmnet in the > > > code. > > > > Huh. But if rmnet has muxing, and IPA supports that, why would you ever > > need multiple lower netdevs? > > From my reading of the code, there is always exactly a 1:1 relationship > between an rmnet netdev an an ipa netdev. rmnet does the encapsulation/ > decapsulation of the qmap data and forwards it to the ipa netdev, > which then just passes data through between a hardware queue and > its netdevice. I'll take your word for it. Seems very odd, given that the whole point of the QMAP header seems to be ... muxing? > [side note: on top of that, rmnet also does "aggregation", which may > be a confusing term that only means transferring multiple frames > at once] Right, but it's not all that much interesting in the context of this discussion. > Sure, I definitely understand what you mean, and I agree that would > be the right way to do it. All I said is that this is not how it was done > in rmnet (this was again my main concern about the rmnet design > after I learned it was required for ipa) ;-) :-) Well, I guess though if the firmware wants us to listen to those on/off messages we'll have to do that one way or the other. Oh. Maybe it's just *because* rmnet is layered on top, and thus you fundamentally cannot do flow control the way I described - not because you have multiple session on the same hardware ring, but because you abstracted the hardware ring away too much ... johannes