resource: Add walk_iomem_res_desc()

Add a new interface, walk_iomem_res_desc(), which walks through
the iomem table by identifying a target with @flags and @desc.
This interface provides the same functionality as
walk_iomem_res(), but does not use strcmp() to @name for better
efficiency.

walk_iomem_res() is deprecated and will be removed in a later
patch.

Requested-by: Borislav Petkov <[e-mail]>
Signed-off-by: Toshi Kani <[e-mail]>
[ Fixup comments. ]
Signed-off-by: Borislav Petkov <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Hanjun Guo <[e-mail]>
Cc: Jakub Sitnicki <[e-mail]>
Cc: Jiang Liu <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Luis R. Rodriguez <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Rafael J. Wysocki <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Toshi Kani <[e-mail]>
Cc: [e-mail]
Cc: linux-mm <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

include/linux/ioport.h

···
 walk_system_ram_res(u64 start, u64 end, void *arg,
 		    int (*func)(u64, u64, void *));
 extern int
+walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start, u64 end,
+		    void *arg, int (*func)(u64, u64, void *));
+extern int
 walk_iomem_res(char *name, unsigned long flags, u64 start, u64 end, void *arg,
 	       int (*func)(u64, u64, void *));
 

kernel/resource.c

···
 EXPORT_SYMBOL(release_resource);
 
 /*
- * Finds the lowest iomem reosurce exists with-in [res->start.res->end)
- * the caller must specify res->start, res->end, res->flags and "name".
- * If found, returns 0, res is overwritten, if not found, returns -1.
- * This walks through whole tree and not just first level children
- * until and unless first_level_children_only is true.
+ * Finds the lowest iomem resource existing within [res->start.res->end).
+ * The caller must specify res->start, res->end, res->flags, and optionally
+ * desc and "name".  If found, returns 0, res is overwritten, if not found,
+ * returns -1.
+ * This function walks the whole tree and not just first level children until
+ * and unless first_level_children_only is true.
  */
-static int find_next_iomem_res(struct resource *res, char *name,
-			       bool first_level_children_only)
+static int find_next_iomem_res(struct resource *res, unsigned long desc,
+			       char *name, bool first_level_children_only)
 {
 	resource_size_t start, end;
 	struct resource *p;
···
 
 	for (p = iomem_resource.child; p; p = next_resource(p, sibling_only)) {
 		if ((p->flags & res->flags) != res->flags)
+			continue;
+		if ((desc != IORES_DESC_NONE) && (desc != p->desc))
 			continue;
 		if (name && strcmp(p->name, name))
 			continue;
···
  * Walks through iomem resources and calls func() with matching resource
  * ranges. This walks through whole tree and not just first level children.
  * All the memory ranges which overlap start,end and also match flags and
+ * desc are valid candidates.
+ *
+ * @desc: I/O resource descriptor. Use IORES_DESC_NONE to skip @desc check.
+ * @flags: I/O resource flags
+ * @start: start addr
+ * @end: end addr
+ *
+ * NOTE: For a new descriptor search, define a new IORES_DESC in
+ * <linux/ioport.h> and set it in 'desc' of a target resource entry.
+ */
+int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
+		u64 end, void *arg, int (*func)(u64, u64, void *))
+{
+	struct resource res;
+	u64 orig_end;
+	int ret = -1;
+
+	res.start = start;
+	res.end = end;
+	res.flags = flags;
+	orig_end = res.end;
+
+	while ((res.start < res.end) &&
+		(!find_next_iomem_res(&res, desc, NULL, false))) {
+
+		ret = (*func)(res.start, res.end, arg);
+		if (ret)
+			break;
+
+		res.start = res.end + 1;
+		res.end = orig_end;
+	}
+
+	return ret;
+}
+
+/*
+ * Walks through iomem resources and calls @func with matching resource
+ * ranges. This walks the whole tree and not just first level children.
+ * All the memory ranges which overlap start,end and also match flags and
  * name are valid candidates.
  *
  * @name: name of resource
  * @flags: resource flags
  * @start: start addr
  * @end: end addr
+ *
+ * NOTE: This function is deprecated and should not be used in new code.
+ * Use walk_iomem_res_desc(), instead.
  */
 int walk_iomem_res(char *name, unsigned long flags, u64 start, u64 end,
 		void *arg, int (*func)(u64, u64, void *))
···
 	res.flags = flags;
 	orig_end = res.end;
 	while ((res.start < res.end) &&
-		(!find_next_iomem_res(&res, name, false))) {
+		(!find_next_iomem_res(&res, IORES_DESC_NONE, name, false))) {
 		ret = (*func)(res.start, res.end, arg);
 		if (ret)
 			break;
···
 	res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 	orig_end = res.end;
 	while ((res.start < res.end) &&
-		(!find_next_iomem_res(&res, NULL, true))) {
+		(!find_next_iomem_res(&res, IORES_DESC_NONE, NULL, true))) {
 		ret = (*func)(res.start, res.end, arg);
 		if (ret)
 			break;
···
 	res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 	orig_end = res.end;
 	while ((res.start < res.end) &&
-		(find_next_iomem_res(&res, NULL, true) >= 0)) {
+		(find_next_iomem_res(&res, IORES_DESC_NONE, NULL, true) >= 0)) {
 		pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT;
 		end_pfn = (res.end + 1) >> PAGE_SHIFT;
 		if (end_pfn > pfn)