linux-kernel - Re: [PATCH v2 0/2] dt-bindings: mtd: partitions: Export special values

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Message-ID: <20231027141122.4a0882c1@xps-13>
Date:   Fri, 27 Oct 2023 14:11:22 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Edward Chow <equu@...nmail.cc>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Lech Perczak <lech.perczak@...lingroup.com>
Subject: Re: [PATCH v2 0/2] dt-bindings: mtd: partitions: Export special
 values

Hi Edward,

equu@...nmail.cc wrote on Fri, 27 Oct 2023 17:46:08 +0800:

> 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. */
>  #define MTDPART_OFS_RETAIN (uint64_t)(-3)
> 
> /* the partition will start at the next erase block. */
>  #define MTDPART_OFS_NXTBLK (uint64_t)(-2)
> 
> /* the partition will start where the previous one ended. */
>  #define MTDPART_OFS_APPEND (uint64_t)(-1)
> 
> (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. */
>  #define MTDPART_SIZ_FULL (0)
> 
> 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.
> 
> Edward Chow (2):
>   dt-bindings: mtd: partitions: Export special values
>   dt-bindings: mtd: partitions: Document special values
> 
>  .../mtd/partitions/fixed-partitions.yaml      | 30 +++++++++++++++++++
>  MAINTAINERS                                   |  2 ++
>  include/dt-bindings/mtd/partitions.h          | 15 ++++++++++
>  3 files changed, 47 insertions(+)
>  create mode 100644 include/dt-bindings/mtd/partitions.h
> 
> --
> 2.42.0

I've expressed my feelings regarding this series in your v1 but it
feels like you are completely ignoring them. As a reminder, I am
opposed to exporting these flags. They are outdated, legacy, have
never been used in DT and were never meant to be.

Thanks, Miquèl