linux-kernel - Re: [PATCH] of/irq: introduce of_has_named

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Date:	Fri, 24 Jul 2015 15:59:39 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of/irq: introduce of_has_named_irqs helper

On Fri, Jul 24, 2015 at 2:26 PM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Fri, Jul 24, 2015 at 02:14:57PM -0500, Rob Herring wrote:
>> On Fri, Jul 24, 2015 at 1:26 PM, Dmitry Torokhov
>> <dmitry.torokhov@...il.com> wrote:
>> > Sometimes drivers might wish to transition from index-based to named
>> > interrupt descriptions. To aid in decision-making when parsing device
>> > tree data let's provide a helper that will indicate the scheme that is
>> > being used.
>>
>> Generally, IRQs are retrieved by platform_get_irq or
>> platform_get_irq_byname. Drivers should not call the of_irq_*
>> functions directly in most cases.
>
> That would be true for platform drivers, but not all devices are
> platform devices.

I should say for drivers, IRQs are retrieved by a bus specific method,
not DT functions. There are 3 cases of drivers using them:

arch/arm/mach-omap2/prm3xxx.c:                  irq_num = of_irq_get(np, 0);
arch/arm/mach-omap2/prm44xx.c:  irq_num = of_irq_get(prm_init_data->np, 0);
drivers/pinctrl/sirf/pinctrl-atlas7.c:          ret = of_irq_get(np, idx);

>> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
>> > ---
>> >
>> > The intent is to it like this:
>> >
>> >         if (of_has_named_irqs(np) {
>> >                 /* Wake IRQ is optional */
>> >                 dev->wakeirq = of_irq_get_byname(np, "wakeup");
>> >                 if (dev->wakeirq < 0 && dev->wakeirq != -ENODATA)
>> >                         return dev->wakeirq;
>> >         }
>>
>> of_irq_get_byname will already return an error if the property is not
>> present. Use that.
>
> I do not like that it returns -EINVAL when property is missing, can we
> change it to return -ENODATA (so it is the same as when the property is
> defined but such name is missing)?

It may be useful to distinguish between those cases. If you want audit
all the callers we could possibly change it though.

Really, I don't understand why you would care about any error code
other than EPROBE_DEFER. If it is optional, then you would want to
continue no matter what is returned.

Rob
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