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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id u10sm4235029otj.75.2021.06.21.10.25.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Jun 2021 10:25:31 -0700 (PDT) Date: Mon, 21 Jun 2021 12:25:28 -0500 From: Bjorn Andersson To: "Enrico Weigelt, metux IT consult" Cc: Linus Walleij , Viresh Kumar , Geert Uytterhoeven , Bartosz Golaszewski , "Enrico Weigelt, metux IT consult" , Viresh Kumar , "Michael S. Tsirkin" , Jason Wang , Vincent Guittot , Bill Mills , Alex Benn?e , stratos-dev@op-lists.linaro.org, "open list:GPIO SUBSYSTEM" , linux-kernel , Stefan Hajnoczi , "Stefano Garzarella --cc virtualization @ lists . linux-foundation . org" , virtualization@lists.linux-foundation.org, Alistair Strachan Subject: Re: [PATCH V3 1/3] gpio: Add virtio-gpio driver Message-ID: References: <10442926ae8a65f716bfc23f32339a6b35e51d5a.1623326176.git.viresh.kumar@linaro.org> <8d58da79-8e54-048b-db89-8c1caaa0320f@metux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8d58da79-8e54-048b-db89-8c1caaa0320f@metux.net> Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Wed 16 Jun 10:52 CDT 2021, Enrico Weigelt, metux IT consult wrote: > On 16.06.21 05:30, Bjorn Andersson wrote: > > > Combined with the virtio-i2c effort this could provide an alternative by > > simply tunneling the busses and GPIOs into Linux and use standard iio > > drivers, for cases where this suits your product requirements better. > > So, you wanna use virtio as logical interface between the two CPUs ? > Interesting idea. Usually folks use rpmsg for those things. > rpmsg is a layer on top of virtio, so this would be an extension of the existing model. There's been discussions (and I believe some implementations) related to bridging I2C requests over rpmsg, but I think it's preferable to standardize around the virtio based bearer directly. > What is running on the secondary CPU ? Some OS like Linux or some bare > metal stuff ? What kind of CPU is that anyways ? > These ideas revolves around platforms that implements something like the "Android Sensor Hub", which provides some resource constraint co-processor that deals with sensor device interaction and processing of the data without waking up the power-hungry ARM cores. Given the focus on power consumption I would guess that these are not going to run Linux. Core-wise I've seen this implemented using primarily ARM and Hexagon cores. Regards, Bjorn