x86, irq: Introduce helper to check whether an IOAPIC has been registered

Introduce acpi_ioapic_registered() to check whether an IOAPIC has already
been registered, it will be used when enabling IOAPIC hotplug.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Len Brown <len.brown@intel.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Link: http://lkml.kernel.org/r/1414387308-27148-18-git-send-email-jiang.liu@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 22 insertions, 0 deletions

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 5427d9b70f75..ddddaed91872 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -826,6 +826,28 @@ int acpi_unregister_ioapic(acpi_handle handle, u32 gsi_base)
 }
 EXPORT_SYMBOL(acpi_unregister_ioapic);
 
+/**
+ * acpi_ioapic_registered - Check whether IOAPIC assoicatied with @gsi_base
+ *                          has been registered
+ * @handle:     ACPI handle of the IOAPIC deivce
+ * @gsi_base:   GSI base associated with the IOAPIC
+ *
+ * Assume caller holds some type of lock to serialize acpi_ioapic_registered()
+ * with acpi_register_ioapic()/acpi_unregister_ioapic().
+ */
+int acpi_ioapic_registered(acpi_handle handle, u32 gsi_base)
+{
+        int ret = 0;
+
+#ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
+        mutex_lock(&acpi_ioapic_lock);
+        ret  = mp_ioapic_registered(gsi_base);
+        mutex_unlock(&acpi_ioapic_lock);
+#endif
+
+        return ret;
+}
+
 static int __init acpi_parse_sbf(struct acpi_table_header *table)
 {
         struct acpi_table_boot *sb;