Re: [PATCH] spi: dt-bindings: Relax node name suffixes again

[Rob Herring <robh@kernel.org>]

On Wed, Sep 16, 2026 at 05:18:27PM +0200, Geert Uytterhoeven wrote:
> From: Geert Uytterhoeven <geert+renesas@glider.be>
> 
> An SPI bus node name can have either a unit address, or a suffix.
> Commit c4fb6880edc15866 ("spi: dt-bindings: restrict node name
> suffixes") restricted these suffixes to decimal numbers.
> However, SPI bus node names with suffixes are typically used for
> board-level bit-banged SPI busses ("spi-gpio"), which live at the root
> of the device tree.  Limiting their node names to numbers is prone to
> conflicts, and may cause silent overwrites, especially when a stack of
> sub-boards or expansion boards is involved.

How is that commit an issue 3 years later?

I've commented on the case which I guess prompted this patch.

BTW, "spi-gpio" or "i2c-gpio" are not good names because you can have 
more than 1 instance.

> 
> Hence relax node name suffixes to alphanumerical characters, so users
> can write more descriptive SPI bus names, which are less prone to
> conflicts.
> 
> While at it, reject empty unit addresses.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202609150228.Nh4nZzbQ-lkp@intel.com
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Other subsystems (regulator, i2c) had similar issues, and numbered
> regulators caused conflicts before, see e.g. commit 45f5d5a9e34d3fe4
> ("arm64: dts: renesas: r8a77995: draak: Fix backlight regulator name").

I2C was a case of "too many to fix". Maybe time to revisit that. 
Regulator binding is a unicorn and not a bus. I really want standard 
names for buses given that's the only way to identify them generically.

Rob