Re: New warning in gpiolib.c

[Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>]

Hi Phil

On Thu, 27 Feb 2025 at 11:20, Phil Elwell <phil@xxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> While running the latest 6.14 release candidate I noticed lot of log
> spam such as this:
>
> [    1.315766] gpio gpiochip0: gpiochip_add_data_with_key:
> get_direction failed: -22
>
> It appears to have been added recently, with the intention that this
> will eventually become a fatal error once all GPIO drivers have been
> "fixed". However, I think the error return here can be appropriate and
> useful.
>
> The GPIO API is lacking a "none of the above" direction, for use with
> pins which can be configured for alternate functions (UART, I2C, SPI,
> etc.). Is it considered preferable to lie in such situations and say
> that the pin is an input? If so, wouldn't that make it impossible to
> detect the genuinely invalid (as far as the API is concerned) case of
> querying the value of a pin without first making it an input?

Link to the thread already discussing this
https://lore.kernel.org/linux-arm-kernel/20250219102750.38519-1-brgl@xxxxxxxx/

  Dave

> Thanks,
>
> Phil