Re: [BUG] SPI broken for SPI based panel drivers

[Sven Van Asbroeck]

On Fri, Dec 4, 2020 at 5:11 AM H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> wrote:
>
> Anyways it is debatable if this is a bug at all. It is just a definition.

I respectfully disagree. Prior to the fix, your panel's active-low chip select
needed to be described in the devicetree with 'spi-cs-high'. That sounds
very much like a bug to me.

> Which is not well documented anywhere.

I agree that documentation can be improved here.
Would you like to submit a patch that improves:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/spi/spi-controller.yaml?h=v5.10-rc6#n28
?
This way, we also get Rob Herring involved, which may lead to more elegant
documentation. He is more likely to respond to a patch than to a question.

>
> What I especially wonder is why you fix that at all in drivers/spi/spi.c
> if polarity inversion is handled in gpiolib.

The reason for that is described in the commit message of
766c6b63aa04 ("spi: fix client driver breakages when using GPIO descriptors")