[PATCH] dt-bindings: mtd: jedec,spi-nor: Document support for more MT25QU parts

[Geert Uytterhoeven]

Hi Michael,

On Thu, Sep 21, 2023 at 6:01 PM Michael Walle <michael at walle.cc> wrote:
> >> We won't break compatibility with older DTBs if we use a list of
> >> compatibles. First the vendor specific one which will use some quirks,
> >> and if that's not available, have as second the generic jedec,spi-nor
> >> to
> >> fallback to.
> >
> > Sure, you should use a list.
> >
> > But the current recommended practice is to not have a list,
> > but just "jedec,spi-nor" (using a list with a new FLASH part name
> > causes checkpatch and dtbs_check warnings). Hence if you follow that
> > recommendation, you will run into compatibility issues with older DTBs
> > when you discover the quirk later, and decide to add it to the list.
>
> The SPI NOR flashes should be auto discoverable. Why do you need a
> compatible string? Quirks can be added to the flash_info database.

This assumes you don't need the quirk before you can identify the part.
I'm not sure that is always the case.

There's a similar issue with Ethernet PHYs on the MDIO bus, which is
why they are gaining proper compatible values in many board DTS files.

> Also note, that one reason *not* to add a particular flash compatible
> is that they are usually interchangeable and OEMs do so. So a where
> today a board might have a macronix flash, tomorrow that board might
> have a gigadevice one for example.

Yeah, that's indeed happening, and it's already an issue.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds