From mboxrd@z Thu Jan 1 00:00:00 1970 From: Srinivas Kandagatla Subject: Re: [PATCH v3 1/3] nvmem: Update the OF binding to use a subnode for the cells list Date: Sun, 10 Jun 2018 11:32:36 +0100 Message-ID: <02d3cba5-01a3-4d8f-55fc-9c7b7fd5e5c1@linaro.org> References: <1521933899-362-1-git-send-email-albeu@free.fr> <1521933899-362-2-git-send-email-albeu@free.fr> <344e0087-7410-aebb-8a66-c6976064df10@linaro.org> <20180417165420.423a691b@avionic-0020> <8c4b48ad-e99e-030a-a4ee-b6df0fa59c79@linaro.org> <20180417180040.04f53495@avionic-0020> <20180418134119.2e587621@avionic-0020> <9f7d2987-b33e-79b5-ae58-2985fd7334e4@linaro.org> <20180418143243.3c23493c@avionic-0020> <20180418153440.187ed16e@avionic-0020> <20180607184155.6da38a01@tock> <0fb0e8e9-e7b8-10c3-fcdd-399c73a33878@linaro.org> <20180608125938.4fd457a0@tock> <20180608190717.55cb185c@tock> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180608190717.55cb185c@tock> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Alban Cc: linux-kernel@vger.kernel.org, Rob Herring , Mark Rutland , David Woodhouse , Brian Norris , Boris Brezillon , Marek Vasut , Richard Weinberger , Cyrille Pitchen , devicetree@vger.kernel.org, linux-mtd@lists.infradead.org List-Id: devicetree@vger.kernel.org On 08/06/18 18:07, Alban wrote: > On Fri, 8 Jun 2018 12:34:12 +0100 > Srinivas Kandagatla wrote: > ... > > I looked into this. It would work fine for the cells but not so nicely > for the nvmem device API. The phandle for the nvmem device would have > to reference the node passed here and not the real device. We would end > up with a DT like this: > > flash@0 { > compatible = "mtd"; > ... > nvmem_dev: nvmem-cells { > compatible = "nvmem-cells"; > ... > }; > }; > > other-device@10 { > ... > nvmem = <&nvmem_dev>; > }; > > Now if there is no cell defined we have this empty child node that make > very little sense, it is just there to accommodate the nvmem API. > NO. This just looks fine! nvmem-cells is the nvmem provider node without which you would not have any provider instance. All this looks as expected! Am not sure what is the problem here! > What I would suggest now is to just change the wording. We don't > deprecate the current binding, but we extend it to allow grouping the > cells in a child node if required. The code to support this is trivial, > (4 lines including error handling) so even if we expect very few > bindings to make use of it it is not going to be maintenance drag. > That would look like this: > > diff --git a/Documentation/devicetree/bindings/nvmem/nvmem.txt b/Documentation/devicetree/bindings/nvmem/nvmem.txt > index fd06c09..085d042 100644 > --- a/Documentation/devicetree/bindings/nvmem/nvmem.txt > +++ b/Documentation/devicetree/bindings/nvmem/nvmem.txt > @@ -19,7 +19,10 @@ Optional properties: > > = Data cells = > These are the child nodes of the provider which contain data cell > -information like offset and size in nvmem provider. > +information like offset and size in nvmem provider. Alternatively the data > +cells can be grouped in a node that has a compatible property set to > +"nvmem-cells". > + > > Required properties: > reg: specifies the offset in byte within the storage device. > diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c > index 4e94a78..3e1369c 100644 > --- a/drivers/nvmem/core.c > +++ b/drivers/nvmem/core.c > @@ -859,6 +859,14 @@ struct nvmem_cell *of_nvmem_cell_get(struct device_node *np, > if (!nvmem_np) > return ERR_PTR(-EINVAL); > > + /* bindings that already have anonymous child nodes can instead put > + * their cells in a child node with an nvmem-cells compatible. */ > + if (of_device_is_compatible(nvmem_np, "nvmem-cells")) { > + nvmem_np = of_get_next_parent(nvmem_np); > + if (!nvmem_np) > + return ERR_PTR(-EINVAL); > + } > + > nvmem = __nvmem_device_get(nvmem_np, NULL, NULL); > of_node_put(nvmem_np); > if (IS_ERR(nvmem)) > > What about it? Let me repeat what I have said in my previous emails: Having a subnode still sounds very fragile to me, and this could be much specific case of MTD provider. We might have instances where this could be sub-sub node of the the original provider for other providers. Also I do not want to bring in Provider specifics layout into nvmem bindings. I can not make myself any clearer than this, Its going to be a NAK from my side for the above reasons! Also, patch I shared should give enough flexibility to various range of providers which have different child node layouts without touching the nvmem bindings. If it works please use it. thanks, srini > > Alban >