dm: Add functions to access a device's children

Devices can have childen that can be addressed by a simple index, the
sequence number or a device tree offset. Add functions to access a child
in each of these ways.

The index is typically used as a fallback when the sequence number is not
available. For example we may use a serial UART with sequence number 0 as
the console, but if no UART has sequence number 0, then we can fall back
to just using the first UART (index 0).

The device tree offset function is useful for buses, where they want to
locate one of their children. The device tree can be scanned to find the
offset of each child, and that offset can then find the device.

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

1 files changed, 93 insertions, 0 deletions

diff --git a/drivers/core/device.c b/drivers/core/device.c
index 848ce3b675..74bb5f0f8e 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -376,3 +376,96 @@ void *dev_get_priv(struct udevice *dev)
 
 	return dev->priv;
 }
+
+static int device_get_device_tail(struct udevice *dev, int ret,
+				  struct udevice **devp)
+{
+	if (ret)
+		return ret;
+
+	ret = device_probe(dev);
+	if (ret)
+		return ret;
+
+	*devp = dev;
+
+	return 0;
+}
+
+int device_get_child(struct udevice *parent, int index, struct udevice **devp)
+{
+	struct udevice *dev;
+
+	list_for_each_entry(dev, &parent->child_head, sibling_node) {
+		if (!index--)
+			return device_get_device_tail(dev, 0, devp);
+	}
+
+	return -ENODEV;
+}
+
+int device_find_child_by_seq(struct udevice *parent, int seq_or_req_seq,
+			     bool find_req_seq, struct udevice **devp)
+{
+	struct udevice *dev;
+
+	*devp = NULL;
+	if (seq_or_req_seq == -1)
+		return -ENODEV;
+
+	list_for_each_entry(dev, &parent->child_head, sibling_node) {
+		if ((find_req_seq ? dev->req_seq : dev->seq) ==
+				seq_or_req_seq) {
+			*devp = dev;
+			return 0;
+		}
+	}
+
+	return -ENODEV;
+}
+
+int device_get_child_by_seq(struct udevice *parent, int seq,
+			    struct udevice **devp)
+{
+	struct udevice *dev;
+	int ret;
+
+	*devp = NULL;
+	ret = device_find_child_by_seq(parent, seq, false, &dev);
+	if (ret == -ENODEV) {
+		/*
+		 * We didn't find it in probed devices. See if there is one
+		 * that will request this seq if probed.
+		 */
+		ret = device_find_child_by_seq(parent, seq, true, &dev);
+	}
+	return device_get_device_tail(dev, ret, devp);
+}
+
+int device_find_child_by_of_offset(struct udevice *parent, int of_offset,
+				   struct udevice **devp)
+{
+	struct udevice *dev;
+
+	*devp = NULL;
+
+	list_for_each_entry(dev, &parent->child_head, sibling_node) {
+		if (dev->of_offset == of_offset) {
+			*devp = dev;
+			return 0;
+		}
+	}
+
+	return -ENODEV;
+}
+
+int device_get_child_by_of_offset(struct udevice *parent, int seq,
+				  struct udevice **devp)
+{
+	struct udevice *dev;
+	int ret;
+
+	*devp = NULL;
+	ret = device_find_child_by_of_offset(parent, seq, &dev);
+	return device_get_device_tail(dev, ret, devp);
+}