linux-kernel - Re: [PATCH v3 05/12] arm64, acpi, numa: NUMA support based on SRAT and SLIT

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Message-ID: <56D6F460.40704@suse.com>
Date:	Wed, 2 Mar 2016 15:10:40 +0100
From:	Matthias Brugger <mbrugger@...e.com>
To:	Robert Richter <robert.richter@...iumnetworks.com>,
	Hanjun Guo <guohanjun@...wei.com>
Cc:	Mark Rutland <mark.rutland@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Steve Capper <steve.capper@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	Shannon Zhao <shannon.zhao@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Ganapatrao Kulkarni <gkulkarni@...iumnetworks.com>,
	linux-arm-kernel@...ts.infradead.org,
	Hanjun Guo <hanjun.guo@...aro.org>
Subject: Re: [PATCH v3 05/12] arm64, acpi, numa: NUMA support based on SRAT
 and SLIT



On 01/02/16 19:09, Robert Richter wrote:
> On 23.01.16 17:39:20, Hanjun Guo wrote:
>
>> @@ -385,10 +386,8 @@ void __init arm64_numa_init(void)
>>   {
>>   	int ret = -ENODEV;
>>
>> -#ifdef CONFIG_OF_NUMA
>>   	if (!numa_off)
>> -		ret = numa_init(arm64_of_numa_init);
>> -#endif
>> +		ret = numa_init(acpi_disabled ? arm64_of_numa_init : arm64_acpi_numa_init);
>>
>>   	if (ret)
>>   		numa_init(dummy_numa_init);
>
> Ok, this style is mostly flavor, some people want #ifdefs (my
> preference), some not. In any case it must build with or without the
> config option set. But first some words why I like #ifdefs:
>
>   * Code is easier to understand as you don't need to look at any other
>     location whether it is enabled or not.
>
>   * You can't break the build if the options are not set. Thus, you
>     also don't need to check if the function is implemented for the
>     unset case (valid for the coder and also the reviewer). This makes
>     things a lot easier.
>
>   * Total number of lines of code that needs to be implement is
>     smaller.
>
> However, if we don't ifdef the code, we need empty functions stubs in
> the header file for them.
>
> Also, the conditional assignment does not reduce the complexity of the
> paths. It just concentrates everything in a single line.
>
> How about the following (similar to x86)?
>
> ----
> 	if (!numa_off) {
> #ifdef CONFIG_ACPI_NUMA
> 		if (!numa_init(acpi_numa_init))
> 			return 0;
> #endif
> #ifdef CONFIG_OF_NUMA
> 		if (!numa_init(of_numa_init))
> 			return 0;
> #endif
> 	}
>
> 	return numa_init(dummy_numa_init);
> ----
>
> Pretty straight and nice.
>

And it solves a compilation error if CONFIG_ACPI is not set and 
therefore asm/acpi.h is not included in linux/acpi.h

Regards,
Matthias