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[24.4.25.55]) by smtp.gmail.com with ESMTPSA id c18sm8717917pgw.17.2020.02.28.00.13.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 28 Feb 2020 00:13:19 -0800 (PST) Date: Fri, 28 Feb 2020 00:13:11 -0800 From: Tao Ren To: Benjamin Herrenschmidt Cc: Mark Rutland , Felipe Balbi , linux-aspeed@lists.ozlabs.org, devicetree@vger.kernel.org, Andrew Jeffery , Greg Kroah-Hartman , openbmc@lists.ozlabs.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Stephen Boyd , Rob Herring , Joel Stanley , taoren@fb.com, Chunfeng Yun , Colin Ian King , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v5 7/7] dt-bindings: usb: add documentation for aspeed usb-vhub Message-ID: <20200228081309.GA4531@taoren-ubuntuvm> References: <20200227230507.8682-1-rentao.bupt@gmail.com> <20200227230507.8682-8-rentao.bupt@gmail.com> <3150424b9e9f5856c747a0fbf44647919f49209d.camel@kernel.crashing.org> <20200228010444.GA19910@taoren-ubuntu-R90MNF91> <2676013663fc8c53e02a5fdaafb1b27e18249b80.camel@kernel.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2676013663fc8c53e02a5fdaafb1b27e18249b80.camel@kernel.crashing.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Fri, Feb 28, 2020 at 02:02:28PM +1100, Benjamin Herrenschmidt wrote: > On Thu, 2020-02-27 at 17:05 -0800, Tao Ren wrote: > > > Also long run I think best is going to have a child node per downstream > > > port, so we create a matching linux struct device. This will make it > > > easier to deal with the other device-controller in the ast2600 which is > > > basically one of these without a vhub above it. > > > > Maybe a dumb question: what would be the proper place to parse the child > > node/properties when they are added? For example, in some usb_gadget_ops > > callback? > > No. What the vhub would do is when it probes, it creates a platform > device for each "port" child node that's linked to the DT node. > > The driver for the device then attaches to it via standard DT matching > and checks if it has a vhub parent or not, and based on that, operates > as a vhub child device or a standalone one. > > (For example, it might have different functions for EP selection since > standalone devices have private EPs rather than a shared pool) > > They can both be in the same module or they can be separate modules > with cross dependencies. > > Cheers, > Ben. I see. It's to describe these downstream devices (such as configurations and according functions) in device tree, which is similar to defining a composite device and linking functions/interfaces via configfs. Thanks for the clarify. Cheers, Tao