linux-kernel - Re: [RFC][PATCH] irq: support IRQ_NESTED_THREAD with non-threaded interrupt handlers

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Message-ID: <AANLkTilb7---Qg1oLwzanKP1RGe04fkAXDtZzz0w9MGz@mail.gmail.com>
Date:	Sat, 5 Jun 2010 15:56:01 +0200
From:	Esben Haabendal <esbenhaabendal@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Esben Haabendal <eha@...edevelopment.dk>,
	linux-kernel@...r.kernel.org, maz@...terjones.org, mingo@...e.hu,
	joachim.eastwood@...ron.com
Subject: Re: [RFC][PATCH] irq: support IRQ_NESTED_THREAD with non-threaded 
	interrupt handlers

I have a board with an I2C PCA9535 chip with two PHY interrupt lines
hooked up to. The pca953x driver calls set_irq_nested_thread on all
irq's on initialization. The PHY driver then calls request_irq, and has
no idea that it should actually be using a threaded handler.

With this patch, the PHY driver is able to work in this scenario
without changes (and so should any other driver using request_irq).

/Esben

On Fri, Jun 4, 2010 at 11:46 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Fri, 4 Jun 2010, Esben Haabendal wrote:
>
>> set_irq_nested_thread() might be called by interrupt controller to
>> supported nested irq thread handling, and with this change, drivers
>> with non-threaded irq handlers can still use the irqs.
>
> What's the problem you are trying to solve ? The above changelog is
> not very useful ?
>
> Thanks,
>
>        tglx
>
>> Signed-off-by: Esben Haabendal <eha@...edevelopment.dk>
>> ---
>>  kernel/irq/chip.c   |    9 ++++++++-
>>  kernel/irq/manage.c |    4 +---
>>  2 files changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>> index b7091d5..8202993 100644
>> --- a/kernel/irq/chip.c
>> +++ b/kernel/irq/chip.c
>> @@ -405,7 +405,14 @@ void handle_nested_irq(unsigned int irq)
>>       desc->status |= IRQ_INPROGRESS;
>>       raw_spin_unlock_irq(&desc->lock);
>>
>> -     action_ret = action->thread_fn(action->irq, action->dev_id);
>> +     if (desc->status & IRQ_NESTED_THREAD && action->thread_fn)
>> +             action_ret = action->thread_fn(action->irq, action->dev_id);
>> +     else {
>> +             local_irq_disable();
>> +             action_ret = action->handler(action->irq, action->dev_id);
>> +             local_irq_enable();
>> +     }
>> +
>>       if (!noirqdebug)
>>               note_interrupt(irq, desc, action_ret);
>>
>> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
>> index 3164ba7..e7bca04 100644
>> --- a/kernel/irq/manage.c
>> +++ b/kernel/irq/manage.c
>> @@ -681,10 +681,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
>>        * Check whether the interrupt nests into another interrupt
>>        * thread.
>>        */
>> -     nested = desc->status & IRQ_NESTED_THREAD;
>> +     nested = (desc->status & IRQ_NESTED_THREAD) && new->thread_fn;
>>       if (nested) {
>> -             if (!new->thread_fn)
>> -                     return -EINVAL;
>>               /*
>>                * Replace the primary handler which was provided from
>>                * the driver for non nested interrupt handling by the
>> --
>> 1.7.1
>>
>>
>>
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-- 
Esben Haabendal, Senior Software Consultant
DoréDevelopment ApS, Ved Stranden 1, 9560 Hadsund, DK-Denmark
Phone: +45 51 92 53 93, E-mail: eha@...edevelopment.dk
WWW: http://www.doredevelopment.dk
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