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

[Daniel Scally]

On 18/01/2021 16:14, Rafael J. Wysocki wrote:
> On Mon, Jan 18, 2021 at 1:37 AM Daniel Scally <djrscally@xxxxxxxxx> wrote:
>> 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.


> 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.


>
>> Signed-off-by: Daniel Scally <djrscally@xxxxxxxxx>
>> ---
>> Changes in v2:
>>         - Used acpi_lpss_dep() as Andy suggested.
>>
>>  drivers/acpi/utils.c    | 34 ++++++++++++++++++++++++++++++++++
>>  include/acpi/acpi_bus.h |  2 ++
>>  2 files changed, 36 insertions(+)
>>
>> diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
>> index 78b38775f18b..ec6a2406a886 100644
>> --- a/drivers/acpi/utils.c
>> +++ b/drivers/acpi/utils.c
>> @@ -831,6 +831,18 @@ bool acpi_lpss_dep(struct acpi_device *adev, acpi_handle handle)
>>         return false;
>>  }
>>
>> +static int acpi_dev_match_by_dep(struct device *dev, const void *data)
>> +{
>> +       struct acpi_device *adev = to_acpi_device(dev);
>> +       const struct acpi_device *dependee = data;
>> +       acpi_handle handle = dependee->handle;
>> +
>> +       if (acpi_lpss_dep(adev, handle))
>> +               return 1;
>> +
>> +       return 0;
>> +}
>> +
>>  /**
>>   * acpi_dev_present - Detect that a given ACPI device is present
>>   * @hid: Hardware ID of the device.
>> @@ -866,6 +878,28 @@ bool acpi_dev_present(const char *hid, const char *uid, s64 hrv)
>>  }
>>  EXPORT_SYMBOL(acpi_dev_present);
>>
>> +/**
>> + * acpi_dev_get_next_dep_dev - Return next ACPI device dependent on input dev
>> + * @adev: Pointer to the dependee device
>> + * @prev: Pointer to the previous dependent device (or NULL for first match)
>> + *
>> + * Return the next ACPI device which declares itself dependent on @adev in
>> + * the _DEP buffer.
>> + *
>> + * The caller is responsible to call put_device() on the returned device.
>> + */
>> +struct acpi_device *acpi_dev_get_next_dep_dev(struct acpi_device *adev,
>> +                                             struct acpi_device *prev)
>> +{
>> +       struct device *start = prev ? &prev->dev : NULL;
>> +       struct device *dev;
>> +
>> +       dev = bus_find_device(&acpi_bus_type, start, adev, acpi_dev_match_by_dep);
>> +
>> +       return dev ? to_acpi_device(dev) : NULL;
>> +}
>> +EXPORT_SYMBOL(acpi_dev_get_next_dep_dev);
>> +
>>  /**
>>   * acpi_dev_get_next_match_dev - Return the next match of ACPI device
>>   * @adev: Pointer to the previous acpi_device matching this @hid, @uid and @hrv
>> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
>> index 02a716a0af5d..33deb22294f2 100644
>> --- a/include/acpi/acpi_bus.h
>> +++ b/include/acpi/acpi_bus.h
>> @@ -683,6 +683,8 @@ static inline bool acpi_device_can_poweroff(struct acpi_device *adev)
>>
>>  bool acpi_dev_hid_uid_match(struct acpi_device *adev, const char *hid2, const char *uid2);
>>
>> +struct acpi_device *
>> +acpi_dev_get_next_dep_dev(struct acpi_device *adev, struct acpi_device *prev);
>>  struct acpi_device *
>>  acpi_dev_get_next_match_dev(struct acpi_device *adev, const char *hid, const char *uid, s64 hrv);
>>  struct acpi_device *
>> --
>> 2.25.1
>>