ACPI: Introduce acpi_os_get_iomem()

Introduce function acpi_os_get_iomem() that may be used by its callers
to get a reference to an ACPI iomap.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

drivers/acpi/osl.c

@@ -285,6 +285,22 @@ acpi_map_vaddr_lookup(acpi_physical_address phys, unsigned int size)
 	return NULL;
 }
 
+void __iomem *acpi_os_get_iomem(acpi_physical_address phys, unsigned int size)
+{
+	struct acpi_ioremap *map;
+	void __iomem *virt = NULL;
+
+	mutex_lock(&acpi_ioremap_lock);
+	map = acpi_map_lookup(phys, size);
+	if (map) {
+		virt = map->virt + (phys - map->phys);
+		map->refcount++;
+	}
+	mutex_unlock(&acpi_ioremap_lock);
+	return virt;
+}
+EXPORT_SYMBOL_GPL(acpi_os_get_iomem);
+
 /* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */
 static struct acpi_ioremap *
 acpi_map_lookup_virt(void __iomem *virt, acpi_size size)

include/linux/acpi_io.h

@@ -10,4 +10,6 @@ static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
        return ioremap_cache(phys, size);
 }
 
+void __iomem *acpi_os_get_iomem(acpi_physical_address phys, unsigned int size);
+
 #endif