Re: [PATCH v2 2/7] acpi: utils: Add function to fetch dependent acpi_devices

Hi Rafael

On 19/01/2021 13:15, Rafael J. Wysocki wrote:

On Mon, Jan 18, 2021 at 9:51 PM Daniel Scally [off-list ref] wrote:

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On 18/01/2021 16:14, Rafael J. Wysocki wrote:

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On Mon, Jan 18, 2021 at 1:37 AM Daniel Scally [off-list ref] wrote:

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In some ACPI tables we encounter, devices use the _DEP method to assert
a dependence on other ACPI devices as opposed to the OpRegions that the
specification intends. We need to be able to find those devices "from"
the dependee, so add a function to parse all ACPI Devices and check if
the include the handle of the dependee device in their _DEP buffer.

What exactly do you need this for?

So, in our DSDT we have devices with _HID INT3472, plus sensors which
refer to those INT3472's in their _DEP method. The driver binds to the
INT3472 device, we need to find the sensors dependent on them.

Well, this is an interesting concept. :-)

Why does _DEP need to be used for that?  Isn't there any other way to
look up the dependent sensors?

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Would it be practical to look up the suppliers in acpi_dep_list instead?

Note that supplier drivers may remove entries from there, but does
that matter for your use case?

Ah - that may work, yes. Thank you, let me test that.

Even if that doesn't work right away, but it can be made work, I would
very much prefer that to the driver parsing _DEP for every device in
the namespace by itself.

This does work; do you prefer it in scan.c, or in utils.c (in which case
with acpi_dep_list declared as external var in internal.h)?