[PATCH 1/3] of: define macro for maximum of_device_is_compatible return value

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

of_device_is_compatible() will return zero on mismatch and a positive
value up to and including (INT_MAX / 2) on match. Knowledge of the upper
bound can be useful to callers, because if inside a loop a maximum score
was achieved, there's usually no point in continuing the search.

Therefore add a macro for INT_MAX / 2 and document it for potential
users.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/of/base.c | 6 ++++--
 include/of.h      | 4 ++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 463db1058ae9..8a42fcee1d40 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -546,7 +546,9 @@ struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
 EXPORT_SYMBOL(of_get_cpu_node);
 
 /** Checks if the given "compat" string matches one of the strings in
- * the device's "compatible" property
+ * the device's "compatible" property. Returns 0 on mismatch and a
+ * positive score on match with the maximum being OF_DEVICE_COMPATIBLE_MAX_SCORE,
+ * which is only returned if the first compatible matched.
  */
 int of_device_is_compatible(const struct device_node *device,
 		const char *compat)
@@ -559,7 +561,7 @@ int of_device_is_compatible(const struct device_node *device,
 	for (cp = of_prop_next_string(prop, NULL); cp;
 	     cp = of_prop_next_string(prop, cp), index++) {
 		if (of_compat_cmp(cp, compat, strlen(compat)) == 0) {
-			score = INT_MAX/2 - (index << 2);
+			score = OF_DEVICE_COMPATIBLE_MAX_SCORE - (index << 2);
 			break;
 		}
 	}
diff --git a/include/of.h b/include/of.h
index 7d1df462d8cf..19b8e7c038a4 100644
--- a/include/of.h
+++ b/include/of.h
@@ -5,6 +5,7 @@
 #include <fdt.h>
 #include <errno.h>
 #include <linux/types.h>
+#include <linux/limits.h>
 #include <linux/list.h>
 #include <linux/err.h>
 #include <asm/byteorder.h>
@@ -124,6 +125,9 @@ int of_fixup_reserved_memory(struct device_node *node, void *data);
 
 struct cdev;
 
+/* Maximum score returned by of_device_is_compatible() */
+#define OF_DEVICE_COMPATIBLE_MAX_SCORE	(INT_MAX / 2)
+
 #ifdef CONFIG_OFTREE
 extern struct device_node *of_read_file(const char *filename);
 extern struct of_reserve_map *of_get_reserve_map(void);
-- 
2.39.2