resource: Use typedef for alignf callback

To make it simpler to declare resource constraint alignf callbacks, add
typedef for it and document it.
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240507102523.57320-5-ilpo.jarvinen@linux.intel.comTested-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>

drivers/pci/bus.c

@@ -176,10 +176,7 @@ static void pci_clip_resource_to_region(struct pci_bus *bus,
 static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
 		resource_size_t size, resource_size_t align,
 		resource_size_t min, unsigned long type_mask,
-		resource_size_t (*alignf)(void *,
-					  const struct resource *,
-					  resource_size_t,
-					  resource_size_t),
+		resource_alignf alignf,
 		void *alignf_data,
 		struct pci_bus_region *region)
 {
@@ -250,10 +247,7 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
 int pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
 		resource_size_t size, resource_size_t align,
 		resource_size_t min, unsigned long type_mask,
-		resource_size_t (*alignf)(void *,
-					  const struct resource *,
-					  resource_size_t,
-					  resource_size_t),
+		resource_alignf alignf,
 		void *alignf_data)
 {
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT

include/linux/ioport.h

@@ -188,6 +188,23 @@ enum {
 #define DEFINE_RES_DMA(_dma)						\
 	DEFINE_RES_DMA_NAMED((_dma), NULL)
 
+/**
+ * typedef resource_alignf - Resource alignment callback
+ * @data:	Private data used by the callback
+ * @res:	Resource candidate range (an empty resource space)
+ * @size:	The minimum size of the empty space
+ * @align:	Alignment from the constraints
+ *
+ * Callback allows calculating resource placement and alignment beyond min,
+ * max, and align fields in the struct resource_constraint.
+ *
+ * Return: Start address for the resource.
+ */
+typedef resource_size_t (*resource_alignf)(void *data,
+					   const struct resource *res,
+					   resource_size_t size,
+					   resource_size_t align);
+
 /* PC/ISA/whatever - the normal PC address spaces: IO and memory */
 extern struct resource ioport_resource;
 extern struct resource iomem_resource;
@@ -207,10 +224,7 @@ extern void arch_remove_reservations(struct resource *avail);
 extern int allocate_resource(struct resource *root, struct resource *new,
 			     resource_size_t size, resource_size_t min,
 			     resource_size_t max, resource_size_t align,
-			     resource_size_t (*alignf)(void *,
-						       const struct resource *,
-						       resource_size_t,
-						       resource_size_t),
+			     resource_alignf alignf,
 			     void *alignf_data);
 struct resource *lookup_resource(struct resource *root, resource_size_t start);
 int adjust_resource(struct resource *res, resource_size_t start,

include/linux/pci.h

@@ -1551,10 +1551,7 @@ int __must_check pci_bus_alloc_resource(struct pci_bus *bus,
 			struct resource *res, resource_size_t size,
 			resource_size_t align, resource_size_t min,
 			unsigned long type_mask,
-			resource_size_t (*alignf)(void *,
-						  const struct resource *,
-						  resource_size_t,
-						  resource_size_t),
+			resource_alignf alignf,
 			void *alignf_data);
 
 

kernel/resource.c

@@ -63,8 +63,7 @@ EXPORT_SYMBOL(iomem_resource);
  */
 struct resource_constraint {
 	resource_size_t min, max, align;
-	resource_size_t (*alignf)(void *, const struct resource *,
-			resource_size_t, resource_size_t);
+	resource_alignf alignf;
 	void *alignf_data;
 };
 
@@ -783,10 +782,7 @@ static int reallocate_resource(struct resource *root, struct resource *old,
 int allocate_resource(struct resource *root, struct resource *new,
 		      resource_size_t size, resource_size_t min,
 		      resource_size_t max, resource_size_t align,
-		      resource_size_t (*alignf)(void *,
-						const struct resource *,
-						resource_size_t,
-						resource_size_t),
+		      resource_alignf alignf,
 		      void *alignf_data)
 {
 	int err;