Re: acpi_device_notify() binding devices that don't seem like they should be bound

[Daniel Scally <djrscally@gmail.com>]

On 08/12/2020 23:48, Daniel Scally wrote:
> Hello again
> 
> On 06/12/2020 00:00, Daniel Scally wrote:
>> INT3472:08 is not an acpi device that seems to be a good candidate for
>> binding to 0000:00:00.0; it just happens to be the first child of
>> PNP0A08:08 that shares _ADR 0 and has _STA not set to 0.
>>
>> The comment within acpi_find_child_device() does imply that there should
>> only ever be a single child device with the same _ADR as the parent, so
>> I suppose this is possibly a case of poor ACPI tables confusing the code
>> a bit; given both PNP0A08:00 and _all_ of the INT3472 devices have _ADR
>> set to zero (as indeed do the machine's cameras), but I'm not
>> knowledgeable enough on ACPI to know whether that's to spec (or at least
>> accounted for). The INT3472 devices themselves do not actually seem to
>> represent a physical device (atleast, not in this case...sometimes they
>> do...), rather they're a dummy being used to simply group some GPIO
>> lines under a common _CRS. The sensors are called out as dependent on
>> these "devices" in their _DEP method, which is already a horrible way of
>> doing things so more broken ACPI being to blame wouldn't surprise me.
>>
>> The other problem that that raises is that there seems to be _no_ good
>> candidate for binding to 0000:00:00.0 that's a child of PNP0A08:00 - the
>> only devices sharing _ADR 0 and having _STA != 0 are those two INT3472
>> entries and the machine's cameras.
> 
> After some more reading, I'm pretty confident that this is the problem
> now - I.E. that those devices having _ADR of 0 is what's causing this
> issue to materialise, and that those values should be set to something
> more appropriate. Still unsure about the best approach to fix it though
> from a kernel point of view; there doesn't seem to be anything out of
> whack in the logic, and I believe (correct me if I'm wrong) there can be
> legitimate instances of child devices sharing _ADR=0 with the parent, so
> the problem becomes how to identify the illegitimate instances so that
> they can be discarded. My experience in this is really limited, so I
> lean towards the conclusion that hard-coding exceptions somewhere might
> be necessary to handle this without resorting to patched ACPI tables.
> Whether that's within acpi_find_child_device() to prevent matching
> occurring there, or else setting the adev->pnp.bus_address to some
> alternate value after creation to compensate.
> 
> I recognise that that's a horrible answer though, so I'm really hoping
> that someone has an idea for how to handle this in a better way.

Oops, missed this crucial line from the spec:

"A device object must contain either an _HID object or an _ADR object,
but should not contain both."

And here's the Device declaration for these objects:

        Device (PMI0)
        {
            Name (_ADR, Zero)  // _ADR: Address
            Name (_HID, "INT3472")  // _HID: Hardware ID
            Name (_CID, "INT3472")  // _CID: Compatible ID
            Name (_DDN, "INCL-CRDD")  // _DDN: DOS Device Name
            Name (_UID, Zero)  // _UID: Unique ID

So that's the broken part rather than the _ADR value of 0 specifically.
That at least gives a jumping off point for some logic to fix rather
than a hardcoded anything, so I'll try to work out a nice way to handle
that (probably ignoring adevs in acpi_find_child_device() with addr=0
and a valid _HID) and submit a patch.

Sorry for the noise, think I'm good now :)