From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: [PATCH RFC 0/4] Adding DT functionality to w1 busses Date: Wed, 27 Jun 2018 21:12:44 +0200 Message-ID: <31d55df2-b5ba-f37e-7566-c73f58ba9b43@zonque.org> References: <20180619212744.794-1-daniel@zonque.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring Cc: zbr@ioremap.net, Mark Rutland , szabolcs.gyurko@tlt.hu, devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Tuesday, June 26, 2018 11:39 PM, Rob Herring wrote: > On Tue, Jun 19, 2018 at 3:27 PM, Daniel Mack wrote: >> In order to fully move battery-supplied devices over to devicetree, the >> onewire subsystem must get some updates. >> >> Currently, the w1 bus system works like this. Device families, such as >> battery controllers etc, are registered to the w1 core. Once a master >> device is probed, it starts scanning the bus. Slave devices that are >> revealed through this scan and that match previously registered >> families are then registered, and their .add_slave() callback is >> invoked. >> >> Some devices, such as the ds2760, use that callback to call >> platform_device_alloc() at runtime with a fixed device name to >> instanciate their only user. That user does the actual work, while the >> slave device merely functions as an I/O proxy. In the user >> implementation, the w1 slave device is accessible through >> dev->parent. > > Looks to me like you are letting the driver structure define the DT > structure. This detail is all irrelevant to DT. > >> >> Now, for devicetree environments, this has to change a bit. First, slave >> devices need to have a matching table so they can be listed as sub-nodes >> of their master bus controller. Second, the core needs to match the >> entries in these tables against the sub-nodes of the master node. >> These two are trivial to do. >> >> The next question is how the w1 slave device and its user(s) are linked >> together. I'm proposing a DT layout with the following example: >> >> onewire { >> compatible = "w1-gpio"; >> >> w1_slave: slave@0 { >> compatible = "maxim,w1-ds2760"; >> }; >> }; >> >> battery-supply { >> compatible = "maxim,ds2760-supply"; >> w1-slave = <&w1_slave>; >> }; > > This should just be one node and a child of the 1-wire master. Yeah, you're right. This also makes the patch set much simpler. Thanks for the feedback - I'll send another round of patches. Daniel