efi_loader: provide function to get last node of a device path

On a block device and its partitions the same protocols can be
installed. To tell the apart we can use the type of the last
node of the device path which is not the end node.

The patch provides a utility function to find this last node.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

diff --git a/include/efi_loader.h b/include/efi_loader.h
index ff59005ff4c1778b7231a0a8bd754791c1bb8ef7..2db4e9c09b0ba0541317b78a63ce5b2fc3d08a58 100644 (file)
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -312,6 +312,9 @@ struct efi_device_path *efi_dp_from_eth(void);
 struct efi_device_path *efi_dp_from_mem(uint32_t mem_type,
                                        uint64_t start_address,
                                        uint64_t end_address);
+/* Determine the last device path node that is not the end node. */
+const struct efi_device_path *efi_dp_last_node(
+                       const struct efi_device_path *dp);
 efi_status_t efi_dp_split_file_path(struct efi_device_path *full_path,
                                    struct efi_device_path **device_path,
                                    struct efi_device_path **file_path);

diff --git a/lib/efi_loader/efi_device_path.c b/lib/efi_loader/efi_device_path.c
index f00a0ce64567ee73b02d0428ef80786924d36f49..c941ea7717b29f58723fb736cec219c16c6d7741 100644 (file)
--- a/lib/efi_loader/efi_device_path.c
+++ b/lib/efi_loader/efi_device_path.c
@@ -208,6 +208,26 @@ struct efi_object *efi_dp_find_obj(struct efi_device_path *dp,
        return efiobj;
 }
 
+/*
+ * Determine the last device path node that is not the end node.
+ *
+ * @dp         device path
+ * @return     last node before the end node if it exists
+ *             otherwise NULL
+ */
+const struct efi_device_path *efi_dp_last_node(const struct efi_device_path *dp)
+{
+       struct efi_device_path *ret;
+
+       if (!dp || dp->type == DEVICE_PATH_TYPE_END)
+               return NULL;
+       while (dp) {
+               ret = (struct efi_device_path *)dp;
+               dp = efi_dp_next(dp);
+       }
+       return ret;
+}
+
 /* return size not including End node: */
 unsigned efi_dp_size(const struct efi_device_path *dp)
 {