[PATCH v1] ACPI / platform: Unregister stale platform devices

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

When the commit 68bdb6773289

  ("ACPI: add support for ACPI reconfiguration notifiers")

introduced reconfiguration notifiers it misses the point that the ACPI table,
which may be loaded and then unloaded via ConfigFS, can contain devices that are
not enumerated by their parents.

In such case the stale platform device is dangling in the system while the rest
of the devices from the same table are already gone.

Introduce acpi_platform_device_remove_notify() notifier that, in similar way to
I²C or SPI buses, unregisters the platform devices on table removal event.

Depends-on: 00500147cbd3 ("drivers: Introduce device lookup variants by ACPI_COMPANION device")
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/acpi/acpi_platform.c | 43 ++++++++++++++++++++++++++++++++++++
 drivers/acpi/scan.c          |  1 +
 2 files changed, 44 insertions(+)

diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
index 00ec4f2bf015..dfcd6210828e 100644
--- a/drivers/acpi/acpi_platform.c
+++ b/drivers/acpi/acpi_platform.c
@@ -31,6 +31,44 @@ static const struct acpi_device_id forbidden_id_list[] = {
 	{"", 0},
 };
 
+static struct platform_device *acpi_platform_device_find_by_adev(struct acpi_device *adev)
+{
+	struct device *dev;
+
+	dev = bus_find_device_by_acpi_dev(&platform_bus_type, adev);
+	return dev ? to_platform_device(dev) : NULL;
+}
+
+static int acpi_platform_device_remove_notify(struct notifier_block *nb,
+					      unsigned long value, void *arg)
+{
+	struct acpi_device *adev = arg;
+	struct platform_device *pdev;
+
+	switch (value) {
+	case ACPI_RECONFIG_DEVICE_ADD:
+		/* Nothing to do here */
+		break;
+	case ACPI_RECONFIG_DEVICE_REMOVE:
+		if (!acpi_device_enumerated(adev))
+			break;
+
+		pdev = acpi_platform_device_find_by_adev(adev);
+		if (!pdev)
+			break;
+
+		platform_device_unregister(pdev);
+		put_device(&pdev->dev);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block acpi_platform_notifier = {
+	.notifier_call = acpi_platform_device_remove_notify,
+};
+
 static void acpi_platform_fill_resource(struct acpi_device *adev,
 	const struct resource *src, struct resource *dest)
 {
@@ -130,3 +168,8 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev,
 	return pdev;
 }
 EXPORT_SYMBOL_GPL(acpi_create_platform_device);
+
+void __init acpi_platform_init(void)
+{
+	acpi_reconfig_notifier_register(&acpi_platform_notifier);
+}
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index aad6be5c0af0..915650bf519f 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -2174,6 +2174,7 @@ int __init acpi_scan_init(void)
 	acpi_pci_root_init();
 	acpi_pci_link_init();
 	acpi_processor_init();
+	acpi_platform_init();
 	acpi_lpss_init();
 	acpi_apd_init();
 	acpi_cmos_rtc_init();
-- 
2.23.0.rc1