[PATCH v3 08/17] xen/device-tree: Add dt_get_pci_domain_nr helper

[Rahul Singh <rahul.singh@xxxxxxx>]

Based Linux commit 41e5c0f81d3e676d671d96a0a1fafb27abfbd9d7

Import the Linux helper of_get_pci_domain_nr. This function will try to
obtain the host bridge domain number by finding a property called
"linux,pci-domain" of the given device node.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
Change in v3:
- Modify commit message to include upstream Linux commit-id not stable
  Linux commit-id
- Remove return value as those are not valid for XEN
Change in v2: Patch introduced in v2
---
 xen/common/device_tree.c      | 12 ++++++++++++
 xen/include/xen/device_tree.h | 17 +++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 53160d61f8..ea93da1725 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -2183,6 +2183,18 @@ void __init dt_unflatten_host_device_tree(void)
     dt_alias_scan();
 }
 
+int dt_get_pci_domain_nr(struct dt_device_node *node)
+{
+    u32 domain;
+    int error;
+
+    error = dt_property_read_u32(node, "linux,pci-domain", &domain);
+    if ( !error )
+        return -EINVAL;
+
+    return (u16)domain;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 3ffe3eb3d2..2297c59ce6 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -832,6 +832,23 @@ int dt_count_phandle_with_args(const struct dt_device_node 
*np,
                                const char *list_name,
                                const char *cells_name);
 
+/**
+ * dt_get_pci_domain_nr - Find the host bridge domain number
+ *            of the given device node.
+ * @node: Device tree node with the domain information.
+ *
+ * This function will try to obtain the host bridge domain number by finding
+ * a property called "linux,pci-domain" of the given device node.
+ *
+ * Return:
+ * * > 0    - On success, an associated domain number.
+ * * -EINVAL    - The property "linux,pci-domain" does not exist.
+ *
+ * Returns the associated domain number from DT in the range [0-0xffff], or
+ * a negative value if the required property is not found.
+ */
+int dt_get_pci_domain_nr(struct dt_device_node *node);
+
 #ifdef CONFIG_DEVICE_TREE_DEBUG
 #define dt_dprintk(fmt, args...)  \
     printk(XENLOG_DEBUG fmt, ## args)
-- 
2.17.1