PCI/ACPI: Prepare stub functions to handle ACPI PCI (hotplug) slots

Prepare two stub functions to handle ACPI PCI slots and ACPI PCI hotplug
slots, which will be invoked by the PCI core when creating/destroying
PCI buses.

It will be used to get rid of ACPI PCI subdrivers for pci_slot and
acpiphp, and eventually remove the ACPI PCI subdriver mechanism.

And it will also be used to handle ACPI PCI (hotplug) slots in a unified
way, both at boot time and for PCI hotplug operations.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Yinghai Lu <yinghai@kernel.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Myron Stowe <myron.stowe@redhat.com>

drivers/pci/pci-acpi.c

@@ -287,6 +287,30 @@ static struct pci_platform_pm_ops acpi_pci_platform_pm = {
 	.run_wake = acpi_pci_run_wake,
 };
 
+void acpi_pci_add_bus(struct pci_bus *bus)
+{
+	acpi_handle handle = NULL;
+
+	if (bus->bridge)
+		handle = ACPI_HANDLE(bus->bridge);
+	if (acpi_pci_disabled || handle == NULL)
+		return;
+
+	/* TODO: add PCI slots and acpiphp hotplug slots */
+}
+
+void acpi_pci_remove_bus(struct pci_bus *bus)
+{
+	/*
+	 * bus->bridge->acpi_node.handle has already been reset to NULL
+	 * when acpi_pci_remove_bus() is called, so don't check ACPI handle.
+	 */
+	if (acpi_pci_disabled)
+		return;
+
+	/* TODO: remove PCI slots and acpiphp hotplug slots */
+}
+
 /* ACPI bus type */
 static int acpi_pci_find_device(struct device *dev, acpi_handle *handle)
 {

include/linux/pci-acpi.h

@@ -41,7 +41,13 @@ static inline acpi_handle acpi_pci_get_bridge_handle(struct pci_bus *pbus)
 
 	return DEVICE_ACPI_HANDLE(dev);
 }
-#endif
+
+void acpi_pci_add_bus(struct pci_bus *bus);
+void acpi_pci_remove_bus(struct pci_bus *bus);
+#else	/* CONFIG_ACPI */
+static inline void acpi_pci_add_bus(struct pci_bus *bus) { }
+static inline void acpi_pci_remove_bus(struct pci_bus *bus) { }
+#endif	/* CONFIG_ACPI */
 
 #ifdef CONFIG_ACPI_APEI
 extern bool aer_acpi_firmware_first(void);