linux-kernel - [RFC PATCH 0/4] mtd: core: OTP nvmem provider support

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Date:   Mon, 22 Mar 2021 19:19:45 +0100
From:   Michael Walle <michael@...le.cc>
To:     linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Rafał Miłecki <rafal@...ecki.pl>,
        Michael Walle <michael@...le.cc>
Subject: [RFC PATCH 0/4] mtd: core: OTP nvmem provider support

The goal is to fetch a (base) MAC address from the OTP region of a SPI NOR
flash.

This is the first part, where I try to add the nvmem provider support to
the MTD core.

I'm not sure about the device tree bindings. Consider the following two
variants:

(1)
    flash@0 {
        ..

        otp {
            compatible = "mtd-user-otp";
            #address-cells = <1>;
            #size-cells = <1>;

            serial-number@0 {
                reg = <0x0 0x8>;
            };
        };
    };

(2)
    flash@0 {
        ..

        otp {
            compatible = "mtd-user-otp";
            #address-cells = <1>;
            #size-cells = <1>;

			some-useful-name {
                compatible = "nvmem-cells";

                serial-number@0 {
                    reg = <0x0 0x8>;
                };
			};
        };
    };

Both bindings use a subnode "opt[-N]". We cannot have the nvmem cells as
children to the flash node because of the legacy partition binding.

(1) seems to be the form which is used almost everywhere in the kernel.
That is, the nvmem cells are just children of the parent node.

(2) seem to be more natural, because there might also be other properties
inside the otp subnode and might be more future-proof.

At the moment this patch implements (1).

Michael Walle (4):
  nvmem: core: allow specifying of_node
  dt-bindings: mtd: add YAML schema for the generic MTD bindings
  dt-bindings: mtd: add OTP bindings
  mtd: core: add OTP nvmem provider support

 .../devicetree/bindings/mtd/common.txt        |  16 +-
 .../devicetree/bindings/mtd/mtd.yaml          | 110 +++++++++++++
 drivers/mtd/mtdcore.c                         | 149 ++++++++++++++++++
 drivers/nvmem/core.c                          |   4 +-
 include/linux/mtd/mtd.h                       |   2 +
 include/linux/nvmem-provider.h                |   2 +
 6 files changed, 267 insertions(+), 16 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/mtd/mtd.yaml

-- 
2.20.1