linux-kernel - Re: [PATCH v2 3/9] irqchip / GIC: Add GIC version support in ACPI MADT

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Date:	Sat, 27 Jun 2015 14:07:58 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	Marc Zyngier <Marc.Zyngier@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Will Deacon <Will.Deacon@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Olof Johansson <olof@...om.net>, Wei Huang <wei@...hat.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [PATCH v2 3/9] irqchip / GIC: Add GIC version support in ACPI
 MADT

On 06/23/2015 12:45 AM, Lorenzo Pieralisi wrote:
> On Fri, Jun 19, 2015 at 09:46:06AM +0100, Hanjun Guo wrote:
>
> [...]
>
>> +
>> +static int __init
>> +match_gic_redist(struct acpi_subtable_header *header, const unsigned long end)
>> +{
>> +	return 0;
>> +}
>> +static bool __init acpi_gic_redist_is_present(void)
>> +{
>> +	int count;
>> +
>> +	/* scan MADT table to find if we have redistributor entries */
>> +	count  =  acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_REDISTRIBUTOR,
>> +					match_gic_redist, 0);
>> +
>> +	/* has at least one GIC redistributor entry */
>> +	if (count > 0)
>> +		return true;
>> +	else
>> +		return false;
>> +}
>
> return count > 0;
>
> What about systems where the redistributor data is in the GICC subtable ? Do
> you treat them as GIC V2 :) ?
>
> On a side note, having to define an empty function like match_gic_redist is
> horrible.
>
> I wonder whether it is not better to refactor map_madt_entry(), create
> a MADT subtable iterator out of it and make that code generic, instead
> of being forced to add these useless MADT handlers just to count
> entries, it is not the first I noticed.

After digging into the code, it seems that we need more discussion for
this comment, you suggested that refactor map_madt_entry() and create
a MADT subtable iterator out of it, but we still need a handler
to handle each subtable entry, right? then it will become another
version of acpi_parse_entries() in drivers/acpi/table.c, and no
improvement to code, did I miss something?

Thanks
Hanjun
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