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Message-ID: <4054f0df-1c1f-da21-71fb-96fb7b3358ff@gmail.com>
Date: Wed, 27 Apr 2022 14:46:51 +0200
From: Rafał Miłecki <zajec5@...il.com>
To: Rob Herring <robh@...nel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
Miquel Raynal <miquel.raynal@...tlin.com>,
Richard Weinberger <richard@....at>,
Vignesh Raghavendra <vigneshr@...com>,
linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, Tom Rini <trini@...sulko.com>,
Ricardo Salveti <ricardo@...ndries.io>,
Michal Simek <michal.simek@...inx.com>,
Jorge Ramirez-Ortiz <jorge@...ndries.io>,
Sean Anderson <seanga2@...il.com>, u-boot@...ts.denx.de,
Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH] dt-bindings: mtd: partitions: add UBI binding
Hi Rob, could you re-review my patch as I provided answers (see below), please?
On 3.03.2022 09:32, Rafał Miłecki wrote:
> On 2.03.2022 22:59, Rob Herring wrote:
>> On Thu, Feb 17, 2022 at 11:24:48AM +0100, Rafał Miłecki wrote:
>>> From: Rafał Miłecki <rafal@...ecki.pl>
>>>
>>> UBI is often used on embedded devices to store UBI volumes with device
>>> configuration / calibration data. Such volumes may need to be documented
>>> and referenced for proper boot & setup.
>>>
>>> Some examples:
>>> 1. U-Boot environment variables
>>> 2. Device calibration data
>>> 3. Default setup (e.g. initial password)
>>>
>>> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
>>> ---
>>> .../bindings/mtd/partitions/ubi.yaml | 67 +++++++++++++++++++
>>> 1 file changed, 67 insertions(+)
>>> create mode 100644 Documentation/devicetree/bindings/mtd/partitions/ubi.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/mtd/partitions/ubi.yaml b/Documentation/devicetree/bindings/mtd/partitions/ubi.yaml
>>> new file mode 100644
>>> index 000000000000..cd081f06d4cb
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mtd/partitions/ubi.yaml
>>> @@ -0,0 +1,67 @@
>>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/mtd/partitions/ubi.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: UBI (Unsorted Block Images) device
>>> +
>>> +description: |
>>> + UBI is a layer providing logical volumes (consisting of logical blocks) on top
>>> + of raw flash devices. It deals with low-level flash issues (bit-flips, bad
>>> + physical eraseblocks, wearing) providing a reliable data storage.
>>> +
>>> + UBI device is built and stored in a single flash partition.
>>> +
>>> + Some (usually embedded) devices use UBI volumes of specific names or indexes
>>> + to store setup / configuration data. This binding allows describing such
>>> + volumes so they can be identified and referenced by consumers.
>>> +
>>> +maintainers:
>>> + - Rafał Miłecki <rafal@...ecki.pl>
>>> +
>>> +allOf:
>>> + - $ref: partition.yaml#
>>> +
>>> +properties:
>>> + compatible:
>>> + const: ubi
>>> +
>>> +patternProperties:
>>> + "^volume-[0-9a-f]+$":
>>> + type: object
>>> + description: UBI volume
>>> + properties:
>>> + volume-name:
>>> + $ref: /schemas/types.yaml#/definitions/string
>>> + volume-id:
>>> + $ref: /schemas/types.yaml#/definitions/uint32
>>> + anyOf:
>>> + - required:
>>> + - volume-name
>>> + - required:
>>> + - volume-id
>>> +
>>> +unevaluatedProperties: false
>>> +
>>> +examples:
>>> + - |
>>> + partitions {
>>> + compatible = "fixed-partitions";
>>> + #address-cells = <1>;
>>> + #size-cells = <1>;
>>> +
>>> + partition@0 {
>>> + compatible = "ubi";
>>> + reg = <0x0000000 0x1000000>;
>>> + label = "filesystem";
>>> +
>>> + env: volume-0 {
>>> + volume-name = "u-boot-env";
>>
>> Why not do 'compatible = "u-boot,env";' to align with normal partitions?
>
> I mean to reserve "compatible" for describing UBI volume content.
>
> If I manage to get
> [PATCH V3] dt-bindings: nvmem: add U-Boot environment variables binding
> https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20220228131250.16943-1-zajec5@gmail.com/
> accepted, it'll allow me to later work on something like:
>
> env: volume-0 {
> compatible = "u-boot,env";
> volume-name = "u-boot-env";
> };
>
> (I believe) I'll need (in the final shape) two properties:
> 1. One for describing UBI volume ("compatible")
> 2. One for identifying UBI volume ("volume-name" / "volume-id")
>
> It's similar design to the "compatible" vs. "reg" in IO hw blocks.
>
>
>> Or 'label'?
>
> I could replace "volume-name" with "label" but someone once told me that:
> > 'label' is supposed to correspond to a sticker on a port or something
> > human identifiable
>
> ;) https://patchwork.ozlabs.org/comment/2812214/
>
> So I don't want to abuse "label" here.
>
>
>> We have enough ways to identify things, I don't think we need another.
>>
>>> + };
>>> +
>>> + calibration: volume-1 {
>>
>> Are 0 and 1 meaningful or just made up indexing?
>
> Made up indexing. I need unique nodenames but @[0-9a-f] doesn't appply here.
>
>
>>> + volume-id = <99>;
>>> + };
>>> + };
>>> + };
>>> --
>>> 2.34.1
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