linux-kernel - Re: [PATCH v5 2/2] ACPI: amba bus probing support

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Message-ID: <CAHp75VdwsQu12+nkJLKaUL8_pbKmR=kmuK+CyED2-b2Np8EjVg@mail.gmail.com>
Date:	Mon, 11 Jan 2016 21:03:52 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Aleksey Makarov <aleksey.makarov@...aro.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Shannon Zhao <shannon.zhao@...aro.org>,
	Vladimir Zapolskiy <vz@...ia.com>, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH v5 2/2] ACPI: amba bus probing support

On Mon, Jan 11, 2016 at 7:24 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Mon, Jan 11, 2016 at 06:26:00PM +0200, Andy Shevchenko wrote:
>> On Mon, Jan 11, 2016 at 5:27 PM, Russell King - ARM Linux
>> <linux@....linux.org.uk> wrote:
>> > On Mon, Jan 11, 2016 at 05:13:20PM +0200, Andy Shevchenko wrote:
>> >> On Mon, Jan 11, 2016 at 3:26 PM, Aleksey Makarov
>> >> <aleksey.makarov@...aro.org> wrote:
>> >> dev->res is 0 before this one, right? Could you use this fact instead
>> >> of address_found flag?
>> >
>> > amba_device_alloc() zero-initialises everything.  However, dev->res is
>> > a struct resource, and I'd prefer _this_ method that the OT is using
>> > to testing some random part of struct resource.
>>
>> So, you mean resource->start = 0 is not enough reliable?
>
> I'd rather not make assumptions about what in a resource is valid
> or not valid.

Fair enough.

>> >> > +               default:
>> >> > +                       dev_warn(&adev->dev, "Invalid resource\n");
>> >>
>> >> Why? Isn't possible to have other resources for the devices?
>> >
>> > AMBA primecell devices have one memory region, and a number of
>> > interrupts.  Other resource types don't make sense.
>>
>> But isn't warning on the other side too noisy?
>
> Why would it be "too noisy" ?  Isn't it saying that the ACPI is in
> error to include more resource types that aren't part of specifying
> the AMBA primecell device?  Maybe it should be dev_err(), because
> it's technically an error...
>
> Are you expecting people to create ACPI tables with a lot of rubbish
> resources attached to these devices?

I'm expecting broken ACPI tables coming from some vendors which is
often the case for some devices.
I would rather leave it as a warning or move to less verbose level.

>> Yes, and in this case ret > 0 should be converted to an appropriate
>> error code, otherwise ACPI core will consider this as a normal
>> execution, right?
>
> You are assuming that it does return a positive non-zero value in the
> first place.

Frankly, I didn't check what that function can return, but I'm sure
that if it will return positive value at some point this will print a
message and tell ACPI that everything okay when it's not.
So, here I suppose to have explicit check for that, or at least (if
you believe that above will never happen) to show that only negative
numbers are possible as error values.

However, I will not insist if Rafael is okay with the original code.

-- 
With Best Regards,
Andy Shevchenko