Re: [PATCH 1/4 v3] spi: Support high CS when using descriptors

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Wed, Apr 3, 2019 at 3:35 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> On Wed, Jan 16, 2019 at 7:27 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:

> > All controllers using GPIO descriptors can by definition
> > support high CS connections, so just enforce this when
> > registering an SPI controller.
>
> But that is guaranteed to be true only for chip selects handled by a GPIO,
> right?
> Native chip selects may still not support SPI_CS_HIGH, depending
> on the controller.
> Before, the bad_bits check in spi_setup() would detect this, and return
> an error. After, this will fail silently.

Yes but only for systems that use descriptors all the way. So dealing
with this is part of the process of converting to using descriptors.
(Thus the other patches in this series.)

Do we have some hardware that supports only active low native
CS but also want to use GPIOs? Because then maybe I should
take a stab at that in particular. If I keep converting drivers to this
then I will hit my head into it sooner or later I suppose.

Yours,
Linus Walleij