resource: Introduce resource_union() for overlapping resources

Some already present users may utilize resource_union() helper.
Provide it for them and for wider use in the future.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/ioport.h

@@ -10,9 +10,10 @@
 #define _LINUX_IOPORT_H
 
 #ifndef __ASSEMBLY__
+#include <linux/bits.h>
 #include <linux/compiler.h>
+#include <linux/minmax.h>
 #include <linux/types.h>
-#include <linux/bits.h>
 /*
  * Resources are tree-like, allowing
  * nesting etc..
@@ -235,6 +236,16 @@ static inline bool resource_overlaps(struct resource *r1, struct resource *r2)
        return r1->start <= r2->end && r1->end >= r2->start;
 }
 
+static inline bool
+resource_union(struct resource *r1, struct resource *r2, struct resource *r)
+{
+	if (!resource_overlaps(r1, r2))
+		return false;
+	r->start = min(r1->start, r2->start);
+	r->end = max(r1->end, r2->end);
+	return true;
+}
+
 /* Convenience shorthand with allocation */
 #define request_region(start,n,name)		__request_region(&ioport_resource, (start), (n), (name), 0)
 #define request_muxed_region(start,n,name)	__request_region(&ioport_resource, (start), (n), (name), IORESOURCE_MUXED)