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

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  Re: [PATCH 1/5] acpi: Add basic device probing infrastructure "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-09-07 23:10 +0200
    Re: [PATCH 1/5] acpi: Add basic device probing infrastructure Marc Zyngier <marc.zyngier@arm.com> - 2015-09-08 12:00 +0200
      Re: [PATCH 1/5] acpi: Add basic device probing infrastructure Hanjun Guo <hanjun.guo@linaro.org> - 2015-09-08 15:10 +0200

#1220403 — Re: [PATCH 1/5] acpi: Add basic device probing infrastructure

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?

Thanks,
Rafael

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#1220666

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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#1220766

On 09/08/2015 05:57 PM, Marc Zyngier wrote:
> 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.

Yes, this framework is for static tables and used at boot time,
sometimes quite early, which is before acpi_early_init().

But for _MAT (which is used for dynamic device configuration), it's
really a good question, I think _MAT is mainly for CPU hotplug, and
it's not related to this framework (for GIC init and clock source).
To hot add/remove a whole ARM SoC with _MAT, I think we need more
time to make the spec ready first, that's long term work, and agian
it's nothing to do with this infrastructure if I understand correctly :)

Thanks
Hanjun
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