Re: [PATCH v16 0/3] mtd: Add support for stacked memories

[Luca Ceresoli]

Hello,

On Tue Feb 3, 2026 at 9:39 PM CET, Luca Ceresoli wrote:
> [TL;DR for v15: as agreed with Amit I'm sending a new iteration of his
> patches to fix the build-time failure due to a module dependency
> loop. Original cover follows.]
>
> This patch series adds stacked support by enhancing the existing mtd-concat
> driver to be more generic.
>
> As background, a few years ago, Bernhard Frauendienst initiated an effort
> [2] to achieve the same, which was later adapted by Miquel [1] to introduce
> stacked mode support. In this approach, partitions to be concatenated were
> specified using a DT property "part-concat" within the partitions
> definition, allowing two MTD devices to function as a single larger one in
> order to be able to define partitions across chip boundaries. However, the
> bindings were not accepted. As a result, the mtd-concat approach was
> dropped, and alternative DT bindings were introduced [3][4][5], describing
> the two flash devices as one. Corresponding SPI core changes to support
> these bindings were later added [6].
>
> While integrating stacked mode support into SPI-NOR, Tudor provided
> additional feedback, leading to discussions about updating the existing
> DT bindings. To address this, I sent an RFC [7] to initiate discussions on
> adapting the DT bindings as suggested by Miquel in [1]. Following that,
> I am now submitting this patch series that updates the virtual concat DT
> bindings and the driver referenced in [1], along with some minor mtdcore
> changes.
> Since I have taken ownership of this effort, I have included Bernhard and
> Miquel under the "Suggested-by" tag.
>
> [1] https://lore.kernel.org/linux-mtd/20191127105522.31445-1-miquel.raynal@xxxxxxxxxxx/
> [2] https://lwn.net/ml/linux-kernel/20180907173515.19990-1-kernel@xxxxxxxxxxxxxxxxx/
> [3] https://github.com/torvalds/linux/commit/f89504300e94524d5d5846ff8b728592ac72cec4
> [4] https://github.com/torvalds/linux/commit/eba5368503b4291db7819512600fa014ea17c5a8
> [5] https://github.com/torvalds/linux/commit/e2edd1b64f1c79e8abda365149ed62a2a9a494b4
> [6] https://github.com/torvalds/linux/commit/4d8ff6b0991d5e86b17b235fc46ec62e9195cb9b
> [7] https://lore.kernel.org/all/20241026075347.580858-1-amit.kumar-mahapatra@xxxxxxx/
>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>

Aargh, I forgot to add my SoB line! Please ignore this series, v17
incoming. Sorry about the mess!

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com