[PATCH 1/6] ACPI: scan: Add acpi_dev_get_next_consumer_dev()

[Daniel Scally <djrscally@xxxxxxxxx>]

In commit b83e2b306736 ("ACPI: scan: Add function to fetch dependent of ACPI
device") we added a means of fetching the first device to declare itself
dependent on another ACPI device in the _DEP method. One assumption
in that patch was that there would only be a single consuming device,
but this has not held.

Extend the functionality by adding a new function that fetches the
next consumer of a supplier device. We can then simplify the original
function by simply calling the new one.

Signed-off-by: Daniel Scally <djrscally@xxxxxxxxx>
---
 drivers/acpi/scan.c     | 47 ++++++++++++++++++++++++++++++++++-------
 include/acpi/acpi_bus.h |  2 ++
 2 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 4463c2eda61e..b3ed664ee1cb 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -2256,9 +2256,21 @@ static void acpi_bus_attach(struct acpi_device *device, bool first_pass)
 		device->handler->hotplug.notify_online(device);
 }
 
-static int acpi_dev_get_first_consumer_dev_cb(struct acpi_dep_data *dep, void *data)
+static int acpi_dev_get_next_consumer_dev_cb(struct acpi_dep_data *dep, void *data)
 {
-	struct acpi_device *adev;
+	struct acpi_device *adev = *(struct acpi_device **)data;
+
+	/*
+	 * If we're passed a 'previous' consumer device then we need to skip
+	 * any consumers until we meet the previous one, and then NULL @data
+	 * so the next one can be returned.
+	 */
+	if (adev) {
+		if (dep->consumer == adev->handle)
+			*(struct acpi_device **)data = NULL;
+
+		return 0;
+	}
 
 	adev = acpi_bus_get_acpi_device(dep->consumer);
 	if (adev) {
@@ -2389,23 +2401,42 @@ bool acpi_dev_ready_for_enumeration(const struct acpi_device *device)
 EXPORT_SYMBOL_GPL(acpi_dev_ready_for_enumeration);
 
 /**
- * acpi_dev_get_first_consumer_dev - Return ACPI device dependent on @supplier
+ * acpi_dev_get_next_consumer_dev - Return the next adev dependent on @supplier
  * @supplier: Pointer to the dependee device
+ * @start: Pointer to the current dependent device
  *
- * Returns the first &struct acpi_device which declares itself dependent on
+ * Returns the next &struct acpi_device which declares itself dependent on
  * @supplier via the _DEP buffer, parsed from the acpi_dep_list.
  *
  * The caller is responsible for putting the reference to adev when it is no
  * longer needed.
  */
-struct acpi_device *acpi_dev_get_first_consumer_dev(struct acpi_device *supplier)
+struct acpi_device *acpi_dev_get_next_consumer_dev(struct acpi_device *supplier,
+						   struct acpi_device *start)
 {
-	struct acpi_device *adev = NULL;
+	struct acpi_device *adev = start;
 
 	acpi_walk_dep_device_list(supplier->handle,
-				  acpi_dev_get_first_consumer_dev_cb, &adev);
+				  acpi_dev_get_next_consumer_dev_cb, &adev);
 
-	return adev;
+	acpi_dev_put(start);
+	return adev == start ? NULL : adev;
+}
+EXPORT_SYMBOL_GPL(acpi_dev_get_next_consumer_dev);
+
+/**
+ * acpi_dev_get_first_consumer_dev - Return ACPI device dependent on @supplier
+ * @supplier: Pointer to the dependee device
+ *
+ * Returns the first &struct acpi_device which declares itself dependent on
+ * @supplier via the _DEP buffer, parsed from the acpi_dep_list.
+ *
+ * The caller is responsible for putting the reference to adev when it is no
+ * longer needed.
+ */
+struct acpi_device *acpi_dev_get_first_consumer_dev(struct acpi_device *supplier)
+{
+	return acpi_dev_get_next_consumer_dev(supplier, NULL);
 }
 EXPORT_SYMBOL_GPL(acpi_dev_get_first_consumer_dev);
 
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index ca88c4706f2b..8b06fef04722 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -720,6 +720,8 @@ bool acpi_dev_hid_uid_match(struct acpi_device *adev, const char *hid2, const ch
 
 void acpi_dev_clear_dependencies(struct acpi_device *supplier);
 bool acpi_dev_ready_for_enumeration(const struct acpi_device *device);
+struct acpi_device *acpi_dev_get_next_consumer_dev(struct acpi_device *supplier,
+						   struct acpi_device *start);
 struct acpi_device *acpi_dev_get_first_consumer_dev(struct acpi_device *supplier);
 struct acpi_device *
 acpi_dev_get_next_match_dev(struct acpi_device *adev, const char *hid, const char *uid, s64 hrv);
-- 
2.25.1