linux-kernel - Re: [PATCH] genirq: Introduce irq_read

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Date:	Tue, 28 Oct 2014 16:05:31 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Bjorn Andersson <bjorn@...o.se>
CC:	Stephen Boyd <sboyd@...eaurora.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Abhijeet Dharmapurikar <adharmap@...eaurora.org>
Subject: Re: [PATCH] genirq: Introduce irq_read_line()

On 28/10/14 15:41, Bjorn Andersson wrote:
> On Sat, Oct 25, 2014 at 2:22 AM, Marc Zyngier <marc.zyngier@....com> wrote:
>> On Sat, Oct 25 2014 at 12:12:55 am BST, Bjorn Andersson <bjorn@...o.se> wrote:
>>> On Fri, Oct 24, 2014 at 10:59 AM, Marc Zyngier <marc.zyngier@....com> wrote:
>>>> I just pushed out a branch:
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git
>>>> irq/irqchip_state
>>>>
>>>> Please let me know if that's useful for you.
>>>>
>>>
>>> I think that my irq_read_line() would be equivalent of
>>> irq_get_irqchip_state(IRQCHIP_STATE_PENDING), i.e. the state of the
>>> interrupt ignoring masking. And the rest would be EINVAL.
>>> So I think this would work out just fine for us!
>>
>> Excellent.
>>
> 
> Hi Marc,
> 
> We gave this some more thought and read up on what "pending" and
> "active" means according to the ARM GIC - PENDING is not what we want
> :(
> 
> In the Qualcomm pmic we have two interrupt status registers
> "interrupt" and "real-time". I think the "interrupt" status register
> would be the one related to your defined constants. However what we
> need to access in our use cases are the "real-time" status register,
> which basically is a representation of the input to the interrupt
> logic.

Fancy. This really look like a i2c GPIO expander (not my best memories...).

> As far as I can see the GIC does not offer anything like that, but I
> hope we could add another constant to your enum list and utilise your
> api for this.
> 
> I'm not entirely sure what we should call it though,
> IRQCHIP_STATE_LEVEL seems somewhat conflicting with level trigger and
> the Qualcomm name IRQCHIP_STATE_REALTIME isn't very self describing.
> Maybe IRQCHIP_STATE_LINE_LEVEL?

Sure, that should be descriptive enough. I really we don't get too many
of these though...

Do you want me to wrap this into the next version?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

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