Re: [PATCH] gpiolib: check if irqchip already has the irq hook replacements

[Hans Verkuil <hverkuil@xxxxxxxxx>]

Hi Linus,

On 09/14/2018 10:47 AM, Linus Walleij wrote:
> On Fri, Sep 14, 2018 at 10:36 AM Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> 
>> Some drivers use a single irqchip for multiple gpiochips. As a result the
>> irqchip hooks are overridden for the first gpiochip that was added, but
>> for the other gpiochip instances this should not happen again, otherwise
>> we would go into an infinite recursion.
>>
>> Check for this, but also log a message that the driver should be fixed
>> since this is bad practice.
>>
>> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> 
> Patch tentatively applied, let's see if we can also get some
> Tested-by from Ludovic!
> 
> Yours,
> Linus Walleij
> 

I have no idea whether it is possible or not, but I think it would be a
good idea to merge this patch with the patch that introduced this problem.

This issue can cause havoc during bisecting for devices that share a
single irqchip with multiple gpiochips and I'm not sure you want to get
that in the mainline kernel.

It would mean rebasing the linux-gpio git tree and if that's impossible,
then so be it, but it might be worth the hassle to avoid a bisecting hell.

I know the linux-media tree is rebased in rare cases to avoid similar issues.

Regards,

	Hans