linux-kernel - Re: [PATCH] dt-bindings: mtd-partitions: Export special values

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Message-ID: <b0e2a2c5-67e5-487e-9023-2fac5ce3ba47@linaro.org>
Date:   Wed, 25 Oct 2023 10:20:10 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Edward Chow <equu@...nmail.cc>, Rob Herring <robh+dt@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: mtd-partitions: Export special values

On 25/10/2023 07:29, Edward Chow wrote:
> There are special "offset" and "size" values defined and documented in
> linux/mtd/partitions.h:
> 
> // consume as much as possible, leaving size after the end of partition.
> 
> // the partition will start at the next erase block.
> 
> // the partition will start where the previous one ended.
> 
> (Though not explicitly, they are compared against variables in uint64_t
> in drivers/mtd/mtdpart.c, so they had better be considered as such.)
> 
> // the partition will extend to the end of the master MTD device.
> 
> These special values could be used to define partitions automatically
> fitting to the size of the master MTD device at runtime.
> 
> However, these values used not to be exported to dt-bindings, thus
> seldom used before, since they might have been only used in numeric form,
> such as "(-1) (-3)" for MTDPART_OFS_RETAIN.
> 
> Now, they are exported in dt-bindings/mtd/partitions.h as 32-bit cell
> values, so 2-cell addressed should be defined to use special offset values,
> such as "MTDPART_OFS_SPECIAL MTDPART_OFS_RETAIN" for MTDPART_OFS_RETAIN in
> linux/mtd/partitions.h. An example is added to fixed-partitions.yaml.
> 
> Signed-off-by: Edward Chow <equu@...nmail.cc>
> ---
>  .../mtd/partitions/fixed-partitions.yaml      | 29 +++++++++++++++++++
>  MAINTAINERS                                   |  2 ++
>  include/dt-bindings/mtd/partitions.h          | 15 ++++++++++
>  3 files changed, 46 insertions(+)
>  create mode 100644 include/dt-bindings/mtd/partitions.h
> 
> diff --git a/Documentation/devicetree/bindings/mtd/partitions/fixed-partitions.yaml b/Documentation/devicetree/bindings/mtd/partitions/fixed-partitions.yaml
> index 331e564f29dc..a939fb52ef76 100644
> --- a/Documentation/devicetree/bindings/mtd/partitions/fixed-partitions.yaml
> +++ b/Documentation/devicetree/bindings/mtd/partitions/fixed-partitions.yaml
> @@ -164,3 +164,32 @@ examples:
>              read-only;
>          };
>      };
> +
> +  - |
> +    partitions {
> +        compatible = "fixed-partitions";
> +        #address-cells = <2>;
> +        #size-cells = <1>;
> +
> +        partition@0 {
> +            label = "bootloader";
> +            reg = <0 0x000000 0x020000>;
> +            read-only;
> +        };
> +
> +        firmware@1 {
> +            label = "firmware";
> +            /* From the end of the last partition, occupying as mush

Use Linux coding style comments.

> +             * as possible, retaining 0x010000 after it,
> +             * "MTDPART_OFS_SPECIAL MTDPART_OFS_NXTBLK" similar to
> +             * this, but always beginning at erase block boundary. */
> +            reg = <MTDPART_OFS_SPECIAL MTDPART_OFS_RETAIN 0x010000>;
> +        };
> +
> +        calibration@2 {
> +            compatible = "fixed-partitions";
> +            label = "calibration";
> +            /* Appending to the last partition, occupying 0x010000 */
> +            reg = <MTDPART_OFS_SPECIAL MTDPART_OFS_APPEND 0x010000>;

And where is any user of this? Example in the bindings is not user. I
would expect that you will change at least one other DTS.

> +        };
> +    };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 668d1e24452d..7d6beadc8b36 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13771,9 +13771,11 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/fixes
>  T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next
>  F:	Documentation/devicetree/bindings/mtd/
>  F:	drivers/mtd/
> +F:	include/dt-bindings/mtd/
>  F:	include/linux/mtd/
>  F:	include/uapi/mtd/
>  
> +

Drop.

>  MEMSENSING MICROSYSTEMS MSA311 DRIVER
>  M:	Dmitry Rokosov <ddrokosov@...rdevices.ru>
>  L:	linux-iio@...r.kernel.org
> diff --git a/include/dt-bindings/mtd/partitions.h b/include/dt-bindings/mtd/partitions.h
> new file mode 100644
> index 000000000000..456a54a1259a
> --- /dev/null
> +++ b/include/dt-bindings/mtd/partitions.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */

Dual license, as asked by checkpatch.

Best regards,
Krzysztof