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

[Daniel Scally <djrscally@xxxxxxxxx>]

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@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