dm: Allow a device to be found by its FDT offset

Each device that was bound from a device tree has an node that caused it to
be bound. Add functions that find and return a device based on a device tree
offset.

Signed-off-by: Simon Glass <sjg@chromium.org>

doc/driver-model/README.txt

@@ -95,12 +95,13 @@ are provided in test/dm. To run them, try:
 You should see something like this:
 
     <...U-Boot banner...>
-    Running 15 driver model tests
+    Running 16 driver model tests
     Test: dm_test_autobind
     Test: dm_test_autoprobe
     Test: dm_test_children
     Test: dm_test_fdt
     Device 'd-test': seq 3 is in use by 'b-test'
+    Test: dm_test_fdt_offset
     Test: dm_test_fdt_pre_reloc
     Test: dm_test_fdt_uclass_seq
     Device 'd-test': seq 3 is in use by 'b-test'

drivers/core/uclass.c

@@ -187,6 +187,30 @@ int uclass_find_device_by_seq(enum uclass_id id, int seq_or_req_seq,
 	return -ENODEV;
 }
 
+static int uclass_find_device_by_of_offset(enum uclass_id id, int node,
+					   struct udevice **devp)
+{
+	struct uclass *uc;
+	struct udevice *dev;
+	int ret;
+
+	*devp = NULL;
+	if (node < 0)
+		return -ENODEV;
+	ret = uclass_get(id, &uc);
+	if (ret)
+		return ret;
+
+	list_for_each_entry(dev, &uc->dev_head, uclass_node) {
+		if (dev->of_offset == node) {
+			*devp = dev;
+			return 0;
+		}
+	}
+
+	return -ENODEV;
+}
+
 /**
  * uclass_get_device_tail() - handle the end of a get_device call
  *
@@ -239,6 +263,17 @@ int uclass_get_device_by_seq(enum uclass_id id, int seq, struct udevice **devp)
 	return uclass_get_device_tail(dev, ret, devp);
 }
 
+int uclass_get_device_by_of_offset(enum uclass_id id, int node,
+				   struct udevice **devp)
+{
+	struct udevice *dev;
+	int ret;
+
+	*devp = NULL;
+	ret = uclass_find_device_by_of_offset(id, node, &dev);
+	return uclass_get_device_tail(dev, ret, devp);
+}
+
 int uclass_first_device(enum uclass_id id, struct udevice **devp)
 {
 	struct uclass *uc;

include/dm/uclass.h

@@ -121,6 +121,22 @@ int uclass_get_device(enum uclass_id id, int index, struct udevice **devp);
  */
 int uclass_get_device_by_seq(enum uclass_id id, int seq, struct udevice **devp);
 
+/**
+ * uclass_get_device_by_of_offset() - Get a uclass device by device tree node
+ *
+ * This searches the devices in the uclass for one attached to the given
+ * device tree node.
+ *
+ * The device is probed to activate it ready for use.
+ *
+ * @id: ID to look up
+ * @node: Device tree offset to search for (if -ve then -ENODEV is returned)
+ * @devp: Returns pointer to device (there is only one for each node)
+ * @return 0 if OK, -ve on error
+ */
+int uclass_get_device_by_of_offset(enum uclass_id id, int node,
+				   struct udevice **devp);
+
 /**
  * uclass_first_device() - Get the first device in a uclass
  *

test/dm/test-fdt.c

@@ -215,3 +215,33 @@ static int dm_test_fdt_uclass_seq(struct dm_test_state *dms)
 	return 0;
 }
 DM_TEST(dm_test_fdt_uclass_seq, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT);
+
+/* Test that we can find a device by device tree offset */
+static int dm_test_fdt_offset(struct dm_test_state *dms)
+{
+	const void *blob = gd->fdt_blob;
+	struct udevice *dev;
+	int node;
+
+	node = fdt_path_offset(blob, "/e-test");
+	ut_assert(node > 0);
+	ut_assertok(uclass_get_device_by_of_offset(UCLASS_TEST_FDT, node,
+						   &dev));
+	ut_asserteq_str("e-test", dev->name);
+
+	/* This node should not be bound */
+	node = fdt_path_offset(blob, "/junk");
+	ut_assert(node > 0);
+	ut_asserteq(-ENODEV, uclass_get_device_by_of_offset(UCLASS_TEST_FDT,
+							    node, &dev));
+
+	/* This is not a top level node so should not be probed */
+	node = fdt_path_offset(blob, "/some-bus/c-test");
+	ut_assert(node > 0);
+	ut_asserteq(-ENODEV, uclass_get_device_by_of_offset(UCLASS_TEST_FDT,
+							    node, &dev));
+
+	return 0;
+}
+
+DM_TEST(dm_test_fdt_offset, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT);