linux-kernel - Re: [PATCH] genirq: Skip chained interrupt trigger configuration if type is IRQ_TYPE

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Date:   Mon, 19 Sep 2016 11:12:13 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <marc.zyngier@....com>
cc:     linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] genirq: Skip chained interrupt trigger configuration if
 type is IRQ_TYPE_NONE

On Mon, 19 Sep 2016, Marc Zyngier wrote:
> There is no point in trying to configure the trigger of a chained
> interrupt if no trigger information has been configured. At best
> this is ignored, and at the worse this confuses the underlying
> irqchip (which is likely not to handle such a thing), and
> unnecessarily alarms the user.
> 
> Only apply the configuration if type is not IRQ_TYPE_NONE.
> 
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Fixes: 1e12c4a9393b ("genirq: Correctly configure the trigger on chained interrupts")
> Link: https://lkml.kernel.org/r/CAMuHMdVW1eTn20=EtYcJ8hkVwohaSuH_yQXrY2MGBEvZ8fpFOg@mail.gmail.com
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  kernel/irq/chip.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index 6373890..26ba565 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -820,6 +820,8 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
>  	desc->name = name;
>  
>  	if (handle != handle_bad_irq && is_chained) {
> +		unsigned int type = irqd_get_trigger_type(&desc->irq_data);
> +
>  		/*
>  		 * We're about to start this interrupt immediately,
>  		 * hence the need to set the trigger configuration.
> @@ -828,8 +830,10 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
>  		 * chained interrupt. Reset it immediately because we
>  		 * do know better.
>  		 */
> -		__irq_set_trigger(desc, irqd_get_trigger_type(&desc->irq_data));
> -		desc->handle_irq = handle;
> +		if (type != IRQ_TYPE_NONE) {
> +			__irq_set_trigger(desc, type);
> +			desc->handle_irq = handle;

Are you really sure that the handler should only be set when the trigger
type is != NONE? I seriously doubt that this is correct.

Thanks,

	tglx