[Xen-devel] [PATCH v7 1/8] xen/arm: pass node to device_tree_for_each_node

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Add a new parameter to device_tree_for_each_node: node, the node to
start the search from.

To avoid scanning device tree, and given that we only care about
relative increments of depth compared to the depth of the initial node,
we set the initial depth to 0. Then, we call func() for every node with
depth > 0.

Don't call func() on the parent node passed as an argument. Clarify the
change in the comment on top of the function. The current callers pass
the root node as argument: it is OK to skip the root node because no
relevant properties are in it, only subnodes.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
---
Changes in v7:
- fix commit message
- use const
- init depth and min_depth to 0

Changes in v6:
- fix code style
- don't call func() on the first node

Changes in v5:
- go back to v3
- code style improvement in acpi/boot.c
- improve comments and commit message
- increase min_depth to avoid parsing siblings
- replace for with do/while loop and increase min_depth to avoid
  scanning siblings of the initial node
- pass only node, calculate depth

Changes in v3:
- improve commit message
- improve in-code comments
- improve code style

Changes in v2:
- new
---
 xen/arch/arm/acpi/boot.c      |  8 +++++---
 xen/arch/arm/bootfdt.c        | 38 ++++++++++++++++++++++-------------
 xen/include/xen/device_tree.h |  6 +++---
 3 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/xen/arch/arm/acpi/boot.c b/xen/arch/arm/acpi/boot.c
index 9b29769a10..bf9c78b02c 100644
--- a/xen/arch/arm/acpi/boot.c
+++ b/xen/arch/arm/acpi/boot.c
@@ -246,9 +246,11 @@ int __init acpi_boot_table_init(void)
      * - the device tree is not empty (it has more than just a /chosen node)
      *   and ACPI has not been force enabled (acpi=force)
      */
-    if ( param_acpi_off || ( !param_acpi_force
-                             && 
device_tree_for_each_node(device_tree_flattened,
-                                                   dt_scan_depth1_nodes, 
NULL)))
+    if ( param_acpi_off)
+        goto disable;
+    if ( !param_acpi_force &&
+         device_tree_for_each_node(device_tree_flattened, 0,
+                                   dt_scan_depth1_nodes, NULL) )
         goto disable;
 
     /*
diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index 891b4b66ff..0ca3c20f05 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -75,9 +75,10 @@ static u32 __init device_tree_get_u32(const void *fdt, int 
node,
 }
 
 /**
- * device_tree_for_each_node - iterate over all device tree nodes
+ * device_tree_for_each_node - iterate over all device tree sub-nodes
  * @fdt: flat device tree.
- * @func: function to call for each node.
+ * @node: parent node to start the search from
+ * @func: function to call for each sub-node.
  * @data: data to pass to @func.
  *
  * Any nodes nested at DEVICE_TREE_MAX_DEPTH or deeper are ignored.
@@ -85,20 +86,22 @@ static u32 __init device_tree_get_u32(const void *fdt, int 
node,
  * Returns 0 if all nodes were iterated over successfully.  If @func
  * returns a value different from 0, that value is returned immediately.
  */
-int __init device_tree_for_each_node(const void *fdt,
+int __init device_tree_for_each_node(const void *fdt, int node,
                                      device_tree_node_func func,
                                      void *data)
 {
-    int node;
-    int depth;
+    /*
+     * We only care about relative depth increments, assume depth of
+     * node is 0 for simplicity.
+     */
+    int depth = 0;
+    const int min_depth = depth;
+    const int first_node = node;
     u32 address_cells[DEVICE_TREE_MAX_DEPTH];
     u32 size_cells[DEVICE_TREE_MAX_DEPTH];
     int ret;
 
-    for ( node = 0, depth = 0;
-          node >=0 && depth >= 0;
-          node = fdt_next_node(fdt, node, &depth) )
-    {
+    do {
         const char *name = fdt_get_name(fdt, node, NULL);
         u32 as, ss;
 
@@ -117,10 +120,17 @@ int __init device_tree_for_each_node(const void *fdt,
         size_cells[depth] = device_tree_get_u32(fdt, node,
                                                 "#size-cells", ss);
 
-        ret = func(fdt, node, name, depth, as, ss, data);
-        if ( ret != 0 )
-            return ret;
-    }
+        /* skip the first node */
+        if ( node != first_node )
+        {
+            ret = func(fdt, node, name, depth, as, ss, data);
+            if ( ret != 0 )
+                return ret;
+        }
+
+        node = fdt_next_node(fdt, node, &depth);
+    } while ( node >= 0 && depth > min_depth );
+
     return 0;
 }
 
@@ -357,7 +367,7 @@ size_t __init boot_fdt_info(const void *fdt, paddr_t paddr)
 
     add_boot_module(BOOTMOD_FDT, paddr, fdt_totalsize(fdt), false);
 
-    device_tree_for_each_node((void *)fdt, early_scan_node, NULL);
+    device_tree_for_each_node((void *)fdt, 0, early_scan_node, NULL);
     early_print_info();
 
     return fdt_totalsize(fdt);
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 83156297e2..9a7a8f2dab 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -158,9 +158,9 @@ typedef int (*device_tree_node_func)(const void *fdt,
 
 extern const void *device_tree_flattened;
 
-int device_tree_for_each_node(const void *fdt,
-                                     device_tree_node_func func,
-                                     void *data);
+int device_tree_for_each_node(const void *fdt, int node,
+                              device_tree_node_func func,
+                              void *data);
 
 /**
  * dt_unflatten_host_device_tree - Unflatten the host device tree
-- 
2.17.1


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