Re: [PATCH 1/6] gpio: make the gpiochip a real device

[Linus Walleij <linus.walleij@linaro.org>]

On Mon, Nov 2, 2015 at 11:31 AM, Johan Hovold <johan@kernel.org> wrote:
> On Thu, Oct 22, 2015 at 10:32:25AM +0200, Linus Walleij wrote:

>> +      * We memset the struct to zero to avoid reentrance issues.
>> +      */
>> +     memset(&chip->device, 0, sizeof(chip->device));
>
> This is an indication of a larger problem.
>
> First of all, you must never register the same device structure twice.
>
> And the larger problem is: With the current interface where a struct
> gpio_chip is passed and registered, how would you prevent the device
> from going away while in use?

OK I see. What about the design pattern elsewhere to pass a
gpiochip desc and have a new gpiochip_register() create the
gpiochip and delete gpiochip_add()?

That's the usual pattern in subsystems.

> You grab a reference to the chip->device when opening the node (in a
> later patch), but it is not used to manage the life time of struct
> gpio_chip.

OK I think the above approach should solve that?

Yours,
Linus Walleij