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Message-ID: <20170308162001.2b7e2304@avionic-0020>
Date: Wed, 8 Mar 2017 16:20:01 +0100
From: Alban <albeu@...e.fr>
To: Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc: Alban <albeu@...e.fr>, linux-kernel@...r.kernel.org,
Mark Rutland <mark.rutland@....com>,
Moritz Fischer <moritz.fischer@...us.com>,
devicetree@...r.kernel.org, Richard Weinberger <richard@....at>,
Marek Vasut <marek.vasut@...il.com>,
Rob Herring <robh+dt@...nel.org>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
linux-mtd@...ts.infradead.org,
Maxime Ripard <maxime.ripard@...e-electrons.com>,
Brian Norris <computersforpeace@...il.com>,
David Woodhouse <dwmw2@...radead.org>,
Cyrille Pitchen <cyrille.pitchen@...el.com>
Subject: Re: [PATCH v2 1/2] doc: bindings: Add bindings documentation for
mtd nvmem
On Tue, 7 Mar 2017 22:01:07 +0100
Boris Brezillon <boris.brezillon@...e-electrons.com> wrote:
> On Tue, 7 Mar 2017 09:26:03 +0100
> Alban <albeu@...e.fr> wrote:
>
> > Config data for drivers, like MAC addresses, is often stored in MTD.
> > Add a binding that define how such data storage can be represented in
> > device tree.
> >
> > Signed-off-by: Alban <albeu@...e.fr>
> > ---
> > Changelog:
> > v2: * Added a "Required properties" section with the nvmem-provider
> > property
> > ---
> > .../devicetree/bindings/nvmem/mtd-nvmem.txt | 33 ++++++++++++++++++++++
> > 1 file changed, 33 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/nvmem/mtd-nvmem.txt
> >
> > diff --git a/Documentation/devicetree/bindings/nvmem/mtd-nvmem.txt b/Documentation/devicetree/bindings/nvmem/mtd-nvmem.txt
> > new file mode 100644
> > index 0000000..8ed25e6
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/nvmem/mtd-nvmem.txt
> > @@ -0,0 +1,33 @@
> > += NVMEM in MTD =
> > +
> > +Config data for drivers, like MAC addresses, is often stored in MTD.
> > +This binding define how such data storage can be represented in device tree.
> > +
> > +An MTD can be defined as an NVMEM provider by adding the `nvmem-provider`
> > +property to their node.
>
> If everyone agrees that this is actually needed, then it should
> definitely go in the nvmem binding doc, and we should patch all nvmem
> providers to define this property (even if we keep supporting nodes
> that are not defining it). I'm not fully convinced yet, but I might be
> wrong.
I really like to hear what the DT people think about this.
> I also think we should take the "nvmem under flash node without partitions"
> into account now, or at least have a clear plan on how we want to represent
> it.
>
> Something like that?
Yes, but with the following extras:
> flash {
nvmem-provider;
> partitions {
> part@X {
> nvmem {
compatible = "nvmem-cells";
> #address-cells = <1>;
> #size-cells = <1>;
>
> cell@Y {
> };
> };
> };
> };
>
> nvmem {
compatible = "nvmem-cells";
> #address-cells = <1>;
> #size-cells = <1>;
>
> cell@X {
> };
> };
> };
>
> Note that patching nvmem core to support the subnode case should be
> pretty easy (see below).
This shouldn't be needed as nothing would change for the NVMEM devices,
what could be added is a check for the "nvmem-provider" property.
To support the proposed binding we would only need a minor change to
of_nvmem_cell_get():
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 408b521ee520..6231ea27c9f4 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -444,6 +444,10 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
if (!config->dev)
return ERR_PTR(-EINVAL);
+ if (config->dev->of_node &&
+ !of_property_read_bool(config->dev->of_node, "nvmem-provider"))
+ return ERR_PTR(-ENODEV);
+
nvmem = kzalloc(sizeof(*nvmem), GFP_KERNEL);
if (!nvmem)
return ERR_PTR(-ENOMEM);
@@ -777,6 +781,15 @@ struct nvmem_cell *of_nvmem_cell_get(struct device_node *np,
if (!nvmem_np)
return ERR_PTR(-EINVAL);
+ /* handle the new cell binding */
+ if (of_device_is_compatible(nvmem_np, "nvmem-cells")) {
+ nvmem_np = of_get_next_parent(cell_np);
+ if (!nvmem_np)
+ return ERR_PTR(-EINVAL);
+ if (!of_property_read_bool(nvmem_np, "nvmem-provider"))
+ return ERR_PTR(-ENODEV);
+ }
+
nvmem = __nvmem_device_get(nvmem_np, NULL, NULL);
if (IS_ERR(nvmem))
return ERR_CAST(nvmem);
> --->8---
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index 408b521ee520..507c6190505b 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -465,7 +465,7 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
> nvmem->priv = config->priv;
> nvmem->reg_read = config->reg_read;
> nvmem->reg_write = config->reg_write;
> - np = config->dev->of_node;
> + np = config->of_node ? : config->dev->of_node;
> nvmem->dev.of_node = np;
> dev_set_name(&nvmem->dev, "%s%d",
> config->name ? : "nvmem", config->id);
> diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
> index cd93416d762e..ec2f5116d62d 100644
> --- a/include/linux/nvmem-provider.h
> +++ b/include/linux/nvmem-provider.h
> @@ -21,6 +21,7 @@ typedef int (*nvmem_reg_write_t)(void *priv, unsigned int offset,
>
> struct nvmem_config {
> struct device *dev;
> + struct device_node *of_node;
> const char *name;
> int id;
> struct module *owner;
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