resource: Export find_resource_space()

PCI bridge window logic needs to find out in advance to the actual
allocation if there is an empty space big enough to fit the window.

Export find_resource_space() for the purpose. Also move the struct
resource_constraint into generic header to be able to use the new
interface.

Link: https://lore.kernel.org/r/20240507102523.57320-7-ilpo.jarvinen@linux.intel.com
Tested-by: Lidong Wang <lidong.wang@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Author: ij-intel

include/linux/ioport.h

@@ -205,6 +205,25 @@ typedef resource_size_t (*resource_alignf)(void *data,
 					   resource_size_t size,
 					   resource_size_t align);
 
+/**
+ * struct resource_constraint - constraints to be met while searching empty
+ *				resource space
+ * @min:		The minimum address for the memory range
+ * @max:		The maximum address for the memory range
+ * @align:		Alignment for the start address of the empty space
+ * @alignf:		Additional alignment constraints callback
+ * @alignf_data:	Data provided for @alignf callback
+ *
+ * Contains the range and alignment constraints that have to be met during
+ * find_resource_space(). @alignf can be NULL indicating no alignment beyond
+ * @align is necessary.
+ */
+struct resource_constraint {
+	resource_size_t min, max, align;
+	resource_alignf alignf;
+	void *alignf_data;
+};
+
 /* PC/ISA/whatever - the normal PC address spaces: IO and memory */
 extern struct resource ioport_resource;
 extern struct resource iomem_resource;
@@ -278,6 +297,9 @@ static inline bool resource_union(const struct resource *r1, const struct resour
 	return true;
 }
 
+int find_resource_space(struct resource *root, struct resource *new,
+			resource_size_t size, struct resource_constraint *constraint);
+
 /* 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)

kernel/resource.c

@@ -48,25 +48,6 @@ struct resource iomem_resource = {
 };
 EXPORT_SYMBOL(iomem_resource);
 
-/**
- * struct resource_constraint - constraints to be met while searching empty
- *				resource space
- * @min:		The minimum address for the memory range
- * @max:		The maximum address for the memory range
- * @align:		Alignment for the start address of the empty space
- * @alignf:		Additional alignment constraints callback
- * @alignf_data:	Data provided for @alignf callback
- *
- * Contains the range and alignment constraints that have to be met during
- * find_resource_space(). @alignf can be NULL indicating no alignment beyond
- * @align is necessary.
- */
-struct resource_constraint {
-	resource_size_t min, max, align;
-	resource_alignf alignf;
-	void *alignf_data;
-};
-
 static DEFINE_RWLOCK(resource_lock);
 
 static struct resource *next_resource(struct resource *p, bool skip_children)
@@ -708,12 +689,13 @@ next:		if (!this || this->end == root->end)
  * * %0		- if successful, @new members start, end, and flags are altered.
  * * %-EBUSY	- if no empty space was found.
  */
-static int find_resource_space(struct resource *root, struct resource *new,
-			       resource_size_t size,
-			       struct resource_constraint *constraint)
+int find_resource_space(struct resource *root, struct resource *new,
+			resource_size_t size,
+			struct resource_constraint *constraint)
 {
 	return  __find_resource_space(root, NULL, new, size, constraint);
 }
+EXPORT_SYMBOL_GPL(find_resource_space);
 
 /**
  * reallocate_resource - allocate a slot in the resource tree given range & alignment.