linux-kernel - Re: [PATCH 1/5] acpi: Add basic device probing infrastructure

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Date:	Tue, 08 Sep 2015 10:57:57 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Len Brown <lenb@...nel.org>, Hanjun Guo <hanjun.guo@...aro.org>,
	Tomasz Nowicki <tn@...ihalf.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	linaro-acpi@...ts.linaro.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/5] acpi: Add basic device probing infrastructure

On 07/09/15 22:29, Rafael J. Wysocki wrote:
> On Friday, September 04, 2015 06:06:48 PM Marc Zyngier wrote:
>> IRQ controllers and timers are the two types of device the kernel
>> requires before being able to use the device driver model.
>>
>> ACPI so far lacks a proper probing infrastructure similar to the one
>> we have with DT, where we're able to declare IRQ chips and
>> clocksources inside the driver code, and let the core code pick it up
>> and call us back on a match. This leads to all kind of really ugly
>> hacks all over the arm64 code and even in the ACPI layer.
>>
>> In order to allow some basic probing based on the ACPI tables,
>> introduce "struct acpi_probe_entry" which contains just enough
>> data and callbacks to match a table, an optional subtable, and
>> call a probe function. A driver can, at build time, register itself
>> and expect being called if the right entry exists in the ACPI
>> table.
>>
>> A acpi_probe_device_init() is provided, taking an ACPI table
>> identifier, and iterating over the registered entries.
> 
> What about things that are provided by the ACPI namespace (eg. via _MAT) rather
> than in static tables?

By the time we get to process non-static tables, the whole probing
infrastructure (including the ACPI interpreter) should be up and
running. I'm not seeing this stuff as a replacement for more dynamic
things - quite the opposite. It is only to be used for early bring-up.

Thanks,

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