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Re: [Xen-devel] [PATCH V1 1/2] xen/device-tree: Add dt_count_phandle_with_args helper



Hi Oleksandr,

On 21/05/2019 18:37, Oleksandr Tyshchenko wrote:
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

Port Linux helper of_count_phandle_with_args for counting
number of phandles in a property.

Please note, this helper is ported from Linux v4.6.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

Acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,


---
     Changes RFC -> V1:
         - Add Linux version which is used as the base.
---
  xen/common/device_tree.c      |  7 +++++++
  xen/include/xen/device_tree.h | 19 +++++++++++++++++++
  2 files changed, 26 insertions(+)

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 8fc401d..65862b5 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -1663,6 +1663,13 @@ int dt_parse_phandle_with_args(const struct 
dt_device_node *np,
                                          index, out_args);
  }
+int dt_count_phandle_with_args(const struct dt_device_node *np,
+                               const char *list_name,
+                               const char *cells_name)
+{
+    return __dt_parse_phandle_with_args(np, list_name, cells_name, 0, -1, 
NULL);
+}
+
  /**
   * unflatten_dt_node - Alloc and populate a device_node from the flat tree
   * @fdt: The parent device tree blob
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 7408a6c..8315629 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -738,6 +738,25 @@ int dt_parse_phandle_with_args(const struct dt_device_node 
*np,
                                 const char *cells_name, int index,
                                 struct dt_phandle_args *out_args);
+/**
+ * dt_count_phandle_with_args() - Find the number of phandles references in a 
property
+ * @np: pointer to a device tree node containing a list
+ * @list_name: property name that contains a list
+ * @cells_name: property name that specifies phandles' arguments count
+ *
+ * Returns the number of phandle + argument tuples within a property. It
+ * is a typical pattern to encode a list of phandle and variable
+ * arguments into a single property. The number of arguments is encoded
+ * by a property in the phandle-target node. For example, a gpios
+ * property would contain a list of GPIO specifies consisting of a
+ * phandle and 1 or more arguments. The number of arguments are
+ * determined by the #gpio-cells property in the node pointed to by the
+ * phandle.
+ */
+int dt_count_phandle_with_args(const struct dt_device_node *np,
+                               const char *list_name,
+                               const char *cells_name);
+
  #ifdef CONFIG_DEVICE_TREE_DEBUG
  #define dt_dprintk(fmt, args...)  \
      printk(XENLOG_DEBUG fmt, ## args)


--
Julien Grall

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