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    SubjectRe: [PATCH v2 2/7] acpi: utils: Add function to fetch dependent acpi_devices
    Hi Daniel,

    Thank you for the patch.

    On Mon, Jan 18, 2021 at 12:34:23AM +0000, Daniel Scally 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.
    >
    > Signed-off-by: Daniel Scally <djrscally@gmail.com>
    > ---
    > 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;
    > +}
    > +

    I think I'd move this just before acpi_dev_get_next_dep_dev() to keep
    the two together.

    > /**
    > * 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

    Maybe acpi_dev_get_next_dependent_dev() ? "dep" could mean either
    dependent or dependency.

    > + * @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);

    Having to loop over all ACPI devices is quite inefficient, but if we
    need a reverse lookup, we don't really have a choice. We could create a
    reverse map, but I don't think it's worth it.

    > +
    > + return dev ? to_acpi_device(dev) : NULL;
    > +}
    > +EXPORT_SYMBOL(acpi_dev_get_next_dep_dev);

    I would have used EXPORT_SYMBOL_GPL. I'm not sure what the policy is in
    the ACPI subsystem, and it's also a personal choice.

    Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    > +
    > /**
    > * 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 *

    --
    Regards,

    Laurent Pinchart

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