Re: [PATCH] gpio: Do not accept gpio chip additions before gpiolib initialization

[Guenter Roeck]

On 03/30/2016 01:37 AM, Alexandre Courbot wrote:
> On Wed, Mar 30, 2016 at 3:20 AM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > Since commit ff2b13592299 ("gpio: make the gpiochip a real device"),
> > attempts to add a gpio chip prior to gpiolib initialization cause the
> > system to crash. Dump a warning to the console and return an error
> > if the situation is encountered.
>
> Mmm I see the problem but this could seriously delay the availability
> of some GPIOs that are useful for early system boot.
>
> I have not followed the GPIO device patches as closely as I should
> have, but shouldn't you be able to register a GPIO chip without
> immediately presenting it to user-space, for internal kernel needs? If
> gpiolib is not initialized, then device-related operations would be
> skipped, and gpiolib_dev_init() could then parse the list of
> registered chips and fix them up when it gets called.
>
> Again, I'm speaking without real knowledge here, but that pattern
> seems more resilent to me.
You are absolutely right, but my knowledge of gpiolib is not good enough
to make that change. See this as a band-gap; it is better than just crashing.

Guenter