linux-kernel - Re: [PATCH] mfd: add MAX8907 core driver

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Message-ID: <5011B32D.1080102@wwwdotorg.org>
Date:	Thu, 26 Jul 2012 15:14:21 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Liam Girdwood <lrg@...com>, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	Gyungoh Yoo <jack.yoo@...im-ic.com>,
	Stephen Warren <swarren@...dia.com>
Subject: Re: [PATCH] mfd: add MAX8907 core driver

On 07/26/2012 02:35 PM, Mark Brown wrote:
> On Thu, Jul 26, 2012 at 01:40:30PM -0600, Stephen Warren wrote:

>> +		if (!irqd_irq_disabled(d) && (value & irq_data->offs)) {
> 
> This looks very suspicious...  why do we need to call 
> irqd_irq_disabled() here?

I believe the status register reflects the unmasked status, it's just
the interrupt signal that's affected by the mask.

>> +static void max8907_irq_enable(struct irq_data *data) +{ +	/*
>> Everything happens in max8907_irq_sync_unlock */ +}
> 
>> +static void max8907_irq_disable(struct irq_data *data) +{ +	/*
>> Everything happens in max8907_irq_sync_unlock */ +}
> 
> The fact that these functions are empty is the second part of the
> above suspicous check for disabled IRQs.  We're just completely
> ignoring the caller here.  What would idiomatically happen is that
> we'd update a variable here then write it out in the unmask.
> 
> If these functions really should be empty then they should be
> omitted.
> 
>> +static int max8907_irq_set_wake(struct irq_data *data, unsigned
>> int on) +{ +	/* Everything happens in max8907_irq_sync_unlock */ 
>> + +	return 0; +}
> 
> Again, this doesn't look clever at all.

So the idea here was that the IRQ core is already maintaining state
which describes which IRQs are enabled/disabled and wake/not. Rather
than have irq_enable/irq_disable/set_wake do nothing but save the same
state to irq_chip-specific structures, I removed the body of those
functions and instead just call irqd_irq_disabled() etc. wherever I
would have accessed the "local" state. Is that not a legitimate design
then?
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