[PATCH 1/2] lib: utils/fdt: Respect compatible string fallback priority

[Samuel Holland]

When matching drivers to DT nodes, always match all drivers against the
first compatible string before considering fallback compatible strings.
This ensures the most specific match is always selected, regardless of
the order of the drivers or match structures, as long as no compatible
string appears in multiple match structures.

Fixes: 1ccc52c427f3 ("lib: utils/fdt: Add helpers for generic driver initialization")
Signed-off-by: Samuel Holland <samuel.holland at sifive.com>
---

 lib/utils/fdt/fdt_driver.c | 46 +++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 21 deletions(-)

diff --git a/lib/utils/fdt/fdt_driver.c b/lib/utils/fdt/fdt_driver.c
index f6707c0e..39385ce9 100644
--- a/lib/utils/fdt/fdt_driver.c
+++ b/lib/utils/fdt/fdt_driver.c
@@ -15,39 +15,43 @@ int fdt_driver_init_by_offset(const void *fdt, int nodeoff,
 {
 	const struct fdt_driver *driver;
 	const struct fdt_match *match;
-	const void *prop;
-	int len, rc;
+	int compat_len, prop_len, rc;
+	const char *compat_str;
 
 	if (!fdt_node_is_enabled(fdt, nodeoff))
 		return SBI_ENODEV;
 
-	prop = fdt_getprop(fdt, nodeoff, "compatible", &len);
-	if (!prop)
+	compat_str = fdt_getprop(fdt, nodeoff, "compatible", &prop_len);
+	if (!compat_str)
 		return SBI_ENODEV;
 
-	while ((driver = *drivers++)) {
-		for (match = driver->match_table; match->compatible; match++) {
-			if (!fdt_stringlist_contains(prop, len, match->compatible))
-				continue;
+	while ((compat_len = strnlen(compat_str, prop_len) + 1) <= prop_len) {
+		for (int i = 0; (driver = drivers[i]); i++)
+			for (match = driver->match_table; match->compatible; match++)
+				if (!memcmp(match->compatible, compat_str, compat_len))
+					goto found;
 
-			if (driver->experimental)
-				sbi_printf("WARNING: %s driver is experimental and may change\n",
-					   match->compatible);
+		compat_str += compat_len;
+		prop_len -= compat_len;
+	}
 
-			rc = driver->init(fdt, nodeoff, match);
-			if (rc < 0) {
-				const char *name;
+	return SBI_ENODEV;
 
-				name = fdt_get_name(fdt, nodeoff, NULL);
-				sbi_printf("%s: %s (%s) init failed: %d\n",
-					   __func__, name, match->compatible, rc);
-			}
+found:
+	if (driver->experimental)
+		sbi_printf("WARNING: %s driver is experimental and may change\n",
+			   match->compatible);
 
-			return rc;
-		}
+	rc = driver->init(fdt, nodeoff, match);
+	if (rc < 0) {
+		const char *name;
+
+		name = fdt_get_name(fdt, nodeoff, NULL);
+		sbi_printf("%s: %s (%s) init failed: %d\n",
+			   __func__, name, match->compatible, rc);
 	}
 
-	return SBI_ENODEV;
+	return rc;
 }
 
 static int fdt_driver_init_scan(const void *fdt,
-- 
2.47.2