Re: [PATCH 1/4] gpiolib: cdev: Flag invalid GPIOs as used

[Linus Walleij]

On Fri, Dec 4, 2020 at 5:47 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:

> When reporting the state of a GPIO to userspace, we never check
> for the actual validity of the line, meaning we report invalid
> lines as being usable. A subsequent request will fail though,
> which is an inconsistent behaviour from a userspace perspective.
>
> Instead, let's check for the validity of the line and report it
> as used if it is invalid. This allows a tool such as gpioinfo
> to report something sensible:
>
> gpiochip3 - 4 lines:
>         line   0:      unnamed       unused   input  active-high
>         line   1:      unnamed       kernel   input  active-high [used]
>         line   2:      unnamed       kernel   input  active-high [used]
>         line   3:      unnamed       unused   input  active-high
>
> In this example, lines 1 and 2 are invalid, and cannot be used by
> userspace.
>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>

This makes sense, so patch applied (unless Bartosz tells me
otherwise, then I'll pull it out again).

Yours,
Linus Walleij