[PATCH v2 4/6] ACPI: scan: Add ACPI device enumerated marker

["Rafael J. Wysocki" <rafael@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Currently, the "visited" flag of ACPI device objects has two roles.
One of them is to indicate that the given ACPI device object has been
enumerated, which basically means that either it has been associated
with a "physical" device representation, or there is no matching
"physical" device representation for it.  The other one is to
indicate that acpi_bus_attach() has processed the device.  That dual
purpose leads to some confusion regarding when that flag should be set
and cleared and by whom.

To address that confusion, add a new bool field called "enumerated"
to struct acpi_device for the purpose of indicating whether or not
the given ACPI device object has been enumerated.  Accordingly, switch
over acpi_device_enumerated() and acpi_device_set/clear_enumerated() to
operate on that field and the "visited" flag will now be only used
internally by the core ACPI device enumeration code.

Namely, acpi_bus_attach() will set flags.visited for a given ACPI
device object after it has been completely processed by that function
and regardless of its current status it needs to be "unattached", for
example by acpi_scan_check_and_detach(), so that acpi_bus_attach() can
process it again.

The rule regarding flags.visited and the "enumerated" field is that the
latter cannot be set until the former has been set and they need to be
cleared in reverse order.

This allows a couple of checks to be dropped from acpi_bus_attach()
and its first_pass argument is not needed any more.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Peixin Xie <peixin.xie@linux.spacemit.com>
---

v1 -> v2:
   * Rebase on top of the new [2-3/6]
   * Drop quote characters from the subject (unnecessary and may get
     in the way in future)
   * Add tag from Peixin Xie

Link to the v1:
https://lore.kernel.org/linux-pci/48339705.fMDQidcC6G@rafael.j.wysocki/

---
 drivers/acpi/scan.c     | 28 +++++++++++++---------------
 include/acpi/acpi_bus.h |  3 ++-
 include/linux/acpi.h    |  4 ++--
 3 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 7208cc515866..2e853add5e60 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -266,8 +266,8 @@ static int acpi_scan_check_and_detach(struct acpi_device *adev, void *p)
 		if (acpi_device_is_enabled(adev))
 			return 0;
 
-		/* Skip device that have not been enumerated. */
-		if (!acpi_device_enumerated(adev)) {
+		/* Skip device that have not been prepared for enumeration. */
+		if (!adev->flags.visited) {
 			dev_dbg(&adev->dev, "Still not enumerated\n");
 			return 0;
 		}
@@ -287,6 +287,7 @@ static int acpi_scan_check_and_detach(struct acpi_device *adev, void *p)
 	if (!(flags & ACPI_SCAN_CHECK_FLAG_EJECT)) {
 		adev->handler = NULL;
 		acpi_device_clear_enumerated(adev);
+		adev->flags.visited = 0;
 	}
 	return 0;
 }
@@ -305,6 +306,7 @@ static int acpi_bus_post_eject(struct acpi_device *adev, void *not_used)
 	}
 
 	acpi_device_clear_enumerated(adev);
+	adev->flags.visited = 0;
 
 	return 0;
 }
@@ -2338,46 +2340,42 @@ static int acpi_scan_attach_handler(struct acpi_device *device)
 	return ret;
 }
 
-static int acpi_bus_attach(struct acpi_device *device, void *first_pass)
+static int acpi_bus_attach(struct acpi_device *device, void *not_used)
 {
-	bool skip = !first_pass && device->flags.visited;
 	acpi_handle ejd;
+	bool skip;
 	int ret;
 
+	skip = !!device->flags.visited;
 	if (skip)
-		goto ok;
+		goto children;
 
 	if (ACPI_SUCCESS(acpi_bus_get_ejd(device->handle, &ejd)))
 		register_dock_dependent_device(device, ejd);
 
 	acpi_bus_get_status(device);
 	/* Skip devices that are not ready for enumeration (e.g. not present) */
-	if (!acpi_dev_ready_for_enumeration(device)) {
-		acpi_device_clear_enumerated(device);
+	if (!acpi_dev_ready_for_enumeration(device))
 		return 0;
-	}
-	if (device->handler)
-		goto ok;
 
 	acpi_ec_register_opregions(device);
 
 	acpi_bus_init_power(device);
 
-	if (device->flags.visited)
-		goto ok;
-
 	ret = acpi_scan_attach_handler(device);
 	if (ret < 0)
 		return 0;
 
+	device->flags.visited = 1;
+
 	if (device->flags.enumeration_by_parent ||
 	    (!ret && (device->pnp.type.platform_id || device->pnp.type.backlight)))
 		acpi_default_enumeration(device);
 	else
 		acpi_device_set_enumerated(device);
 
-ok:
-	acpi_dev_for_each_child(device, acpi_bus_attach, first_pass);
+children:
+	acpi_dev_for_each_child(device, acpi_bus_attach, NULL);
 
 	if (!skip && device->handler && device->handler->hotplug.notify_online)
 		device->handler->hotplug.notify_online(device);
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 1a45e0d521d8..46ac4a33ae2c 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -468,6 +468,7 @@ struct acpi_device {
 	struct list_head physical_node_list;
 	struct mutex physical_node_lock;
 	void (*remove)(struct acpi_device *);
+	bool enumerated;
 };
 
 /* Non-device subnode */
@@ -654,7 +655,7 @@ void acpi_set_modalias(struct acpi_device *adev, const char *default_id,
 
 static inline bool acpi_device_enumerated(struct acpi_device *adev)
 {
-	return adev && adev->flags.initialized && adev->flags.visited;
+	return adev && adev->flags.initialized && adev->enumerated;
 }
 
 /*
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index ddacac812094..2e9e49e2e665 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -782,12 +782,12 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *,
 
 static inline void acpi_device_set_enumerated(struct acpi_device *adev)
 {
-	adev->flags.visited = true;
+	adev->enumerated = true;
 }
 
 static inline void acpi_device_clear_enumerated(struct acpi_device *adev)
 {
-	adev->flags.visited = false;
+	adev->enumerated = false;
 }
 
 enum acpi_reconfig_event  {
-- 
2.51.0