acpi, pci, spibus -- tying it all together

[Yuri Pankov]

Konstantin Belousov wrote:
> On Sun, Sep 09, 2018 at 10:25:44AM +0300, Yuri Pankov wrote:
>> I have modified intelspi to attach to SPI master (Sunrise Point-H Serial
>> IO SPI) located on pci bus, and on attach I have the spibus0 and spibus1
>> buses added.
>>
>> As spibus is not self-enumerating, the only way to find the slave device
>> I need is via acpi bus probe, that works, but I don't see a way to make
>> it a child of spibus1 (where it's located).
>>
>> In ACPI terms it looks like the below (from DSDT):
>>
>> ...
>> \_SB_.PCI0.SPI0 "Device (SPI0)"
>> \_SB_.PCI0.SPI1 "Device (SPI1)"
>> ...
>> Scope (SPI1) {
>>       Device (SPIT) {
>>           ...here comes all the data we need,
>>              including the ACPI ID we can probe...
>>       }
>> }
>> ...
>>
>> I hope that made at least some sense.  And the question is if there any
>> existing way of tying it all together, and adding that slave device to
>> the spibus1 (which only knows about hinted children at the moment)?
> 
> I had very similar situation where I wrote NVDIMM driver.
> 
> The suggestion I got was to implement DEVICE_IDENTIFY() method.  It
> gets the driver_t and the parent bus device_t arguments.  In the method,
> you create children' device_t, iterating over the ACPI enumerated entries.
> Practically, you would use acpica AcpiWalkNamespace(ACPI_TYPE_DEVICE, ...)
> function and call BUS_ADD_CHILD() when needed.  Set the ACPI handle for
> the created child.  [Get the Intel' ACPICA reference manual to understand
> the KPI].
> 
> Then probe does nothing, and attach verifies against the handle.
> 
> You can see that in https://kib.kiev.ua/kib/nvdimm.7.patch
> nvdimm_identify(), nvdimm_foreach_acpi(), and nvdimm_create_dev().

Thank you, it was helpful indeed, especially the walk part.