[PATCH 3/4] pinctrl/rockchip: add a queue for deferred pin output settings on probe

[Linus Walleij]

On Tue, Sep 14, 2021 at 12:49 AM Heiko Stuebner <heiko at sntech.de> wrote:

> The separation of pinctrl and gpio drivers created a tiny window where
> a pinconfig setting might produce a null-pointer dereference.
>
> The affected device were rk3288-veyron devices in this case.
>
> Pinctrl-hogs are claimed when the pinctrl driver is registered,
> at which point their pinconfig settings will be applied.
> At this time the now separate gpio devices will not have been created
> yet and the matching driver won't have probed yet, making the gpio->foo()
> call run into a null-ptr.
>
> As probing is not really guaranteed to have been completed at a specific
> time, introduce a queue that can hold the output settings until the gpio
> driver has probed and will (in a separate patch) fetch the elements
> of the list.
>
> We expect the gpio driver to empty the list, but will nevertheless empty
> it ourself on remove if that didn't happen.
>
> Fixes: 9ce9a02039de ("pinctrl/rockchip: drop the gpio related codes")
> Signed-off-by: Heiko Stuebner <heiko at sntech.de>

Hm this is not very elegant but what can we do.
Tentatively applied for fixes.

Can we not use device links to get around this?

Yours,
Linus Walleij