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Fri, 31 May 2019 23:59:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1559347183; bh=tJJKl5ehmjDb2KK6XeMOmnd1rblvf2TEFa0oPKfTx5A=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=JhHqfqgmdNVqLrmRdouTw0Seluy99Trhgv3NmXlFn69xRxPpycBc/Q+DRSfAeVwu4 JTEboKLfLKX0c13lS4DlpcSurxqakUSwUHvxF/LXUHDnPuoHKctksui16YqOi10b83 IBD+oLcK1w2+MnQzgPq0KGIsSeRbdNA1g0f1wxfU= MIME-Version: 1.0 Date: Fri, 31 May 2019 17:59:43 -0600 From: Subash Abhinov Kasiviswanathan To: Bjorn Andersson Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver In-Reply-To: <20190531233306.GB25597@minitux> References: <20190531035348.7194-1-elder@linaro.org> <065c95a8-7b17-495d-f225-36c46faccdd7@linaro.org> <20190531233306.GB25597@minitux> Message-ID: X-Sender: subashab@codeaurora.org User-Agent: Roundcube Webmail/1.2.5 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190531_165946_304453_50B36D4F X-CRM114-Status: GOOD ( 22.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: DTML , syadagir@codeaurora.org, Eric Caruso , Arnd Bergmann , Dan Williams , Networking , linux-arm-msm@vger.kernel.org, Ilias Apalodimas , Linux Kernel Mailing List , evgreen@chromium.org, abhishek.esse@gmail.com, Linux ARM , Alex Elder , linux-soc@vger.kernel.org, David Miller , cpratapa@codeaurora.org, Ben Chan Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2019-05-31 17:33, Bjorn Andersson wrote: > On Fri 31 May 13:47 PDT 2019, Alex Elder wrote: > >> On 5/31/19 2:19 PM, Arnd Bergmann wrote: >> > On Fri, May 31, 2019 at 6:36 PM Alex Elder wrote: >> >> On 5/31/19 9:58 AM, Dan Williams wrote: >> >>> On Thu, 2019-05-30 at 22:53 -0500, Alex Elder wrote: >> >>> >> >>> My question from the Nov 2018 IPA rmnet driver still stands; how does >> >>> this relate to net/ethernet/qualcomm/rmnet/ if at all? And if this is >> >>> really just a netdev talking to the IPA itself and unrelated to >> >>> net/ethernet/qualcomm/rmnet, let's call it "ipa%d" and stop cargo- >> >>> culting rmnet around just because it happens to be a net driver for a >> >>> QC SoC. >> >> >> >> First, the relationship between the IPA driver and the rmnet driver >> >> is that the IPA driver is assumed to sit between the rmnet driver >> >> and the hardware. >> > >> > Does this mean that IPA can only be used to back rmnet, and rmnet >> > can only be used on top of IPA, or can or both of them be combined >> > with another driver to talk to instead? >> >> No it does not mean that. >> >> As I understand it, one reason for the rmnet layer was to abstract >> the back end, which would allow using a modem, or using something >> else (a LAN?), without exposing certain details of the hardware. >> (Perhaps to support multiplexing, etc. without duplicating that >> logic in two "back-end" drivers?) >> >> To be perfectly honest, at first I thought having IPA use rmnet >> was a cargo cult thing like Dan suggested, because I didn't see >> the benefit. I now see why one would use that pass-through layer >> to handle the QMAP features. >> >> But back to your question. The other thing is that I see no >> reason the IPA couldn't present a "normal" (non QMAP) interface >> for a modem. It's something I'd really like to be able to do, >> but I can't do it without having the modem firmware change its >> configuration for these endpoints. My access to the people who >> implement the modem firmware has been very limited (something >> I hope to improve), and unless and until I can get corresponding >> changes on the modem side to implement connections that don't >> use QMAP, I can't implement such a thing. >> > > But any such changes would either be years into the future or for > specific devices and as such not applicable to any/most of devices on > the market now or in the coming years. > > > But as Arnd points out, if the software split between IPA and rmnet is > suboptimal your are encouraged to fix that. > > Regards, > Bjorn The split rmnet design was chosen because we could place rmnet over any transport - IPA, PCIe (https://lkml.org/lkml/2018/4/26/1159) or USB. rmnet registers a rx handler, so the rmnet packet processing itself happens in the same softirq when packets are queued to network stack by IPA. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel