cpukit/rtems-fdt: test and fix index search by offset

The rtems_fdt_subnode_offset and rtems_fdt_get_name try to binary
search the entries index by the DTB offset, but the index is sorted
by alphabetically by the name, so the search is broken. Replace these
searches by directly calling the libfdt functions. Since the DTB offset
is known, the performance hit for invoking the libfdt should not be too
much.

Closes #5606.

cpukit/libmisc/rtems-fdt/rtems-fdt.c

@@ -289,38 +289,6 @@ static int rtems_fdt_index_find_by_name(
   return -FDT_ERR_NOTFOUND;
 }
 
-/**
- * For a given FDT offset, find the corresponding path name.
- */
-static const char *rtems_fdt_index_find_name_by_offset(
-  rtems_fdt_index *index,
-  int              offset
-)
-{
-  int min = 0;
-  int max = index->num_entries;
-
-  /*
-   * Binary search for the offset.
-   */
-  while ( min < max ) {
-    int middle = ( min + max ) / 2;
-    if ( offset < index->entries[ middle ].offset ) {
-      /* Look lower than here. */
-      max = middle;
-    } else if ( offset > index->entries[ middle ].offset ) {
-      /* Look higher than here. */
-      min = middle + 1;
-    } else {
-      /* Found it. */
-      return index->entries[ middle ].name;
-    }
-  }
-
-  /* Didn't find it. */
-  return NULL;
-}
-
 void rtems_fdt_init_handle( rtems_fdt_handle *handle )
 {
   if ( handle ) {
@@ -662,20 +630,11 @@ int rtems_fdt_subnode_offset(
   const char       *name
 )
 {
-  char        full_name[ 256 ];
-  const char *path;
-
   if ( !handle->blob ) {
     return -RTEMS_FDT_ERR_INVALID_HANDLE;
   }
 
-  path = rtems_fdt_index_find_name_by_offset(
-    &handle->blob->index,
-    parentoffset
-  );
-  snprintf( full_name, sizeof( full_name ), "%s/%s", path, name );
-
-  return rtems_fdt_index_find_by_name( &handle->blob->index, full_name );
+  return fdt_subnode_offset( handle->blob->blob, parentoffset, name );
 }
 
 int rtems_fdt_path_offset( rtems_fdt_handle *handle, const char *path )
@@ -693,15 +652,7 @@ const char *rtems_fdt_get_name(
     return NULL;
   }
 
-  const char *name = rtems_fdt_index_find_name_by_offset(
-    &handle->blob->index,
-    nodeoffset
-  );
-  if ( name && length ) {
-    *length = strlen( name );
-  }
-
-  return name;
+  return fdt_get_name( handle->blob->blob, nodeoffset, length );
 }
 
 int rtems_fdt_first_prop_offset( rtems_fdt_handle *handle, int nodeoffset )

testsuites/libtests/fdt01/init.c

@@ -71,6 +71,13 @@ void test_getprop(
   int               plen
 );
 
+void test_subnode(
+  rtems_fdt_handle *handle,
+  int               offset,
+  const char       *sname,
+  int               slen
+);
+
 const char rtems_test_name[] = "FDT 01";
 
 /* triplets of identical uncompressed/compressed dtbs */
@@ -166,6 +173,38 @@ void test_getprop(
   rtems_test_assert( strncmp( namep, pname, name_len ) == 0 );
 }
 
+void test_subnode(
+  rtems_fdt_handle *handle,
+  int               offset,
+  const char       *sname,
+  int               slen
+)
+{
+  int         idx1, idx2;
+  const char *name;
+  int         len = 0;
+  int         parent_offset;
+
+  name = rtems_fdt_get_name( handle, offset, &len );
+  rtems_test_assert( strncmp( name, sname, slen ) == 0 );
+
+  parent_offset = rtems_fdt_parent_offset( handle, offset );
+  rtems_test_assert( parent_offset >= 0 );
+
+  idx1 = rtems_fdt_subnode_offset( handle, parent_offset, sname );
+  rtems_test_assert( idx1 >= 0 );
+  rtems_test_assert( idx1 != parent_offset );
+
+  idx2 = rtems_fdt_subnode_offset_namelen(
+    handle,
+    parent_offset,
+    sname,
+    slen
+  );
+  rtems_test_assert( idx2 >= 0 );
+  rtems_test_assert( idx1 == idx2 );
+}
+
 rtems_task Init( rtems_task_argument ignored )
 {
   (void) ignored;
@@ -173,6 +212,8 @@ rtems_task Init( rtems_task_argument ignored )
   int               rc;
   size_t            i;
   uint32_t          val;
+  int               idx;
+  const char       *name = "interrupt-controller@c000000";
   rtems_fdt_handle  handles[ NUM_DTB ];
 
   TEST_BEGIN();
@@ -233,6 +274,21 @@ rtems_task Init( rtems_task_argument ignored )
   val = cpu_to_fdt32( 0x2 );
   test_getprop( &handles[ 0 ], "clocks", &val, sizeof( val ) );
 
+  idx = rtems_fdt_node_offset_by_compatible(
+    &handles[ 6 ],
+    -1,
+    "riscv,plic0"
+  );
+  rtems_test_assert( idx >= 0 );
+  test_subnode( &handles[ 6 ], idx, name, strlen( name ) );
+  /* try again with length truncated to the unit address */
+  test_subnode(
+    &handles[ 6 ],
+    idx,
+    name,
+    (const char *) memchr( name, '@', strlen( name ) ) - name
+  );
+
   for ( i = 0; i < NUM_DTB; i++ ) {
     rc = rtems_fdt_unload( &handles[ i ] );
     rtems_test_assert( rc == 0 );