Re: [PATCH 2/2] ACPI: scan: Fix _STA getting called on devices with unmet dependencies

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Sunday, March 28, 2021 1:20:00 PM CEST Hans de Goede wrote:
> Commit 71da201f38df ("ACPI: scan: Defer enumeration of devices with
> _DEP lists") dropped the following 2 lines from acpi_init_device_object():
> 
> 	/* Assume there are unmet deps until acpi_device_dep_initialize() runs */
> 	device->dep_unmet = 1;
> 
> Leaving the initial value of dep_unmet at the 0 from the kzalloc(). This
> causes the acpi_bus_get_status() call in acpi_add_single_object() to
> actually call _STA, even though there maybe unmet deps, leading to errors
> like these:
> 
> [    0.123579] ACPI Error: No handler for Region [ECRM] (00000000ba9edc4c)
>                [GenericSerialBus] (20170831/evregion-166)
> [    0.123601] ACPI Error: Region GenericSerialBus (ID=9) has no handler
>                (20170831/exfldio-299)
> [    0.123618] ACPI Error: Method parse/execution failed
>                \_SB.I2C1.BAT1._STA, AE_NOT_EXIST (20170831/psparse-550)
> 
> Fix this by moving the acpi_scan_dep_init() call done for devices added
> during the second pass done by acpi_bus_scan() to inside
> acpi_add_single_object(), so that dep_unmet is properly initialized
> before the acpi_bus_get_status() call.

I wonder why the change below can't be made instead.

The behavior would be closer to the original then AFAICS.

---
 drivers/acpi/scan.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -1647,6 +1647,8 @@ void acpi_init_device_object(struct acpi
 	device_initialize(&device->dev);
 	dev_set_uevent_suppress(&device->dev, true);
 	acpi_init_coherency(device);
+	/* Assume there are unmet deps to start with. */
+	device->dep_unmet = 1;
 }
 
 void acpi_device_add_finalize(struct acpi_device *device)
@@ -1957,7 +1959,13 @@ static acpi_status acpi_bus_check_add(ac
 		return AE_CTRL_DEPTH;
 
 	acpi_scan_init_hotplug(device);
-	if (!check_dep)
+	/*
+	 * If check_dep is true at this point, the device has no dependencies,
+	 * or the creation of the device object would have been postponed above.
+	 */
+	if (check_dep)
+		device->dep_unmet = 0;
+	else
 		acpi_scan_dep_init(device);
 
 out: