[PATCH] spi: handle spi-rx/tx-bus-width = 0 (no RX/TX line)

[Alexey Charkov]

On Fri, Jul 3, 2026 at 3:42 PM r00tnomade <r00tnomade at proton.me> wrote:
>
> Hey team,
>
> I just put together a patch to fix that annoying "spi-rx-bus-width 0 not supported" warning we keep seeing on every boot for the Flipper One.
>
> Turns out the Device Tree binding explicitly says a value of 0 means the line isn't wired up (like a write-only display with MISO left disconnected). However, spi_child_post_bind() was only looking for 1, 2, 4, or 8, so it threw a warning even though our DT is completely correct.
>
> What I changed:
>
> Added the SPI_NO_RX and SPI_NO_TX flags to include/spi.h (matching Linux's naming convention).
>
> Handled the 0 case explicitly in drivers/spi/spi-uclass.c so it applies those flags instead of triggering the warning.
>
> This should finally clear up the boot logs and close out issue #33. Let me know if it looks good to merge!

Hi Sami,

Looks like your patch body didn't get through. Would you mind
resending in plaintext using b4 or git send-email?

Please also see
https://source.denx.de/u-boot/u-boot/-/blob/master/doc/develop/process.rst?ref_type=heads

Best regards,
Alexey