From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rhyland Klein Subject: Re: [RFC v2 1/3] power_supply: Define Binding for supplied-nodes Date: Fri, 22 Feb 2013 17:05:10 -0500 Message-ID: <5127EB96.3000206@nvidia.com> References: <1361488272-21010-1-git-send-email-rklein@nvidia.com> <1361488272-21010-2-git-send-email-rklein@nvidia.com> <5127CAF9.1030506@wwwdotorg.org> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5127CAF9.1030506-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Stephen Warren Cc: Anton Vorontsov , David Woodhouse , Grant Likely , Rob Herring , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Mark Brown List-Id: devicetree@vger.kernel.org On 2/22/2013 2:46 PM, Stephen Warren wrote: > On 02/21/2013 04:11 PM, Rhyland Klein wrote: >> This property is meant to be used in device nodes which represent >> power_supply devices that wish to provide a list of supplies to >> which they provide power. A common case is a AC Charger with >> the batteries it powers. >> diff --git a/Documentation/devicetree/bindings/power_supply/power_supply.txt b/Documentation/devicetree/bindings/power_supply/power_supply.txt >> +Optional Properties: >> + - power-supply : This property is added to a supply in order to list the >> + devices which supply it power, referenced by their phandles. > DT properties that reference resources are usually named in the plural, > so "power-supplies" would be more appropriate here. > > It seems plausible that a single DT node could represent/instantiate > multiple separate supply objects. I think we want to employ the standard > pattern of rather than just . > > That way, each supply that can supply others would have something like a > #supply-cells = , where n is the number of cells that the supply uses > to name the multiple supplies provided by that node. 0 would be a common > value here. 1 might be used for a node that represents many supplies. > > When a client supply uses a providing supply as the supply(!), do you > need any flags to parameterize the connection? If so, that might be > cause for a supplier to have a larger #supply-cells, so the flags could > be represented. > > That all said, regulators assume 1 node == 1 regulator, so an > alternative would be for a multi-supply node to include a child node per > supply, e.g.: > > power@xxx { > ... > supply1 { > ... > }; > supply2 { > ... > }; > }; > > client { > supplies = <&supply1> <&supply2>; > }; > > I don't recall why regulators went for the style above rather than the > #supply-cells style. Cc Mark Brown for any comment here. > > Also, do supplies and regulators need to inter-operate in any way (e.g. > reference each-other in DT)? > >> +Example: >> + >> + usb-charger: power@e { >> + compatible = "some,usb-charger"; >> + ... >> + }; >> + >> + ac-charger: power@e { >> + compatible = "some,ac-charger"; >> + ... >> + }; >> + >> + battery@b { >> + compatible = "some,battery"; >> + ... >> + power-supply = <&usb-charger>, <&ac-charger>; >> + }; The "connection" between supplier and supplies isn't really a hard connection. Essentially, the core code uses the names/nodes in the list and iterates over all the power_supplies that are registered and does matching. I don't have any experience working with a single node that would spawn multiple supplies, though the situation I am sure is possible. I am interested to see what the consensus is around this design for multiple supplies, as I don't have a preference either way. -rhyland -- nvpublic