Proposal: U-Boot MTD (rewriting old story)

[Simon Glass]

Hi Jagan,

On Tue, 3 Aug 2021 at 09:01, Jagan Teki <jagan at amarulasolutions.com> wrote:
>
> Yes, this is the old discussion and triggered again now since we had a
> discussion on the last U-Boot contributor call.
>
> I will brief the main points here, as most of the details are
> mentioned in previous threads.
>
> Here are the couple of old and new implementations on the SPI-NOR side.
>
> http://u-boot.10912.n7.nabble.com/PATCH-v10-00-27-dm-Generic-MTD-Subsystem-with-SPI-NOR-interface-tt315694.html#none
> http://u-boot.10912.n7.nabble.com/PATCH-0-5-mtd-Implement-MTD-UCLASS-use-SPINOR-td419538.html#a419541
> https://patchwork.ozlabs.org/project/uboot/cover/20200709111709.68904-1-jagan@amarulasolutions.com/
>
> Idea is to
> 1. Create MTD_UCLASS, already present
> 2. Create DM MTD Operations, above patchset does.
> 3. Create Flash specific MTD UClass's like
>     UCLASS_NAND
>     UCLASS_SPI_NAND
>     UCLASS_SPI_NOR
>     UCLASS_NOR
>     UCLASS_UBI
> and register to UCLASS_MTD as interface slaves like how MMC, SCSI are
> registered to UCLASS_BLK
> 4. Sync only respective flash specific code, and drop __UBOOT__
> 5. Interface mtd, sf, and nand commands to UCLASS_MTD.

This all seems good to me.

>
> Hard points:
> 1. Hard to arrange Linux specific code and drop unneeded _UBOOT_ code,
> but possible.
> 2. Requires a lot of testing.

Let's add simple emulators for NAND, SPI_NAND and UBI. We already have
one for SPI_NOR I believe. That will be a good long-term investment.

Regards,
Simon