dm: core: Add a few more specific child-finding functions

Add two functions which can find a child device by uclass or by name.
The first is useful with Multi-Function-Devices (MFDs) to find one of a
particular type. The second is useful when only the name is known.
Signed-off-by: NSimon Glass <sjg@chromium.org>

drivers/core/device.c

@@ -699,6 +699,40 @@ int device_find_first_inactive_child(struct udevice *parent,
 	return -ENODEV;
 }
 
+int device_find_first_child_by_uclass(struct udevice *parent,
+				      enum uclass_id uclass_id,
+				      struct udevice **devp)
+{
+	struct udevice *dev;
+
+	*devp = NULL;
+	list_for_each_entry(dev, &parent->child_head, sibling_node) {
+		if (device_get_uclass_id(dev) == uclass_id) {
+			*devp = dev;
+			return 0;
+		}
+	}
+
+	return -ENODEV;
+}
+
+int device_find_child_by_name(struct udevice *parent, const char *name,
+			      struct udevice **devp)
+{
+	struct udevice *dev;
+
+	*devp = NULL;
+
+	list_for_each_entry(dev, &parent->child_head, sibling_node) {
+		if (!strcmp(dev->name, name)) {
+			*devp = dev;
+			return 0;
+		}
+	}
+
+	return -ENODEV;
+}
+
 struct udevice *dev_get_parent(const struct udevice *child)
 {
 	return child->parent;

include/dm/device.h

@@ -525,6 +525,8 @@ int device_find_next_child(struct udevice **devp);
  * This is used to locate an existing child of a device which is of a given
  * uclass.
  *
+ * The device is NOT probed
+ *
  * @parent:	Parent device to search
  * @uclass_id:	Uclass to look for
  * @devp:	Returns device found, if any
@@ -534,6 +536,29 @@ int device_find_first_inactive_child(struct udevice *parent,
 				     enum uclass_id uclass_id,
 				     struct udevice **devp);
 
+/**
+ * device_find_first_child_by_uclass() - Find the first child of a device in uc
+ *
+ * @parent: Parent device to search
+ * @uclass_id:	Uclass to look for
+ * @devp: Returns first child device in that uclass, if any
+ * @return 0 if found, else -ENODEV
+ */
+int device_find_first_child_by_uclass(struct udevice *parent,
+				      enum uclass_id uclass_id,
+				      struct udevice **devp);
+
+/**
+ * device_find_child_by_name() - Find a child by device name
+ *
+ * @parent:	Parent device to search
+ * @name:	Name to look for
+ * @devp:	Returns device found, if any
+ * @return 0 if found, else -ENODEV
+ */
+int device_find_child_by_name(struct udevice *parent, const char *name,
+			      struct udevice **devp);
+
 /**
  * device_has_children() - check if a device has any children
  *

test/dm/test-fdt.c

@@ -631,3 +631,30 @@ static int dm_test_fdt_phandle(struct unit_test_state *uts)
 	return 0;
 }
 DM_TEST(dm_test_fdt_phandle, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT);
+
+/* Test device_find_first_child_by_uclass() */
+static int dm_test_first_child(struct unit_test_state *uts)
+{
+	struct udevice *i2c, *dev, *dev2;
+
+	ut_assertok(uclass_first_device_err(UCLASS_I2C, &i2c));
+	ut_assertok(device_find_first_child_by_uclass(i2c, UCLASS_RTC, &dev));
+	ut_asserteq_str("rtc@43", dev->name);
+	ut_assertok(device_find_child_by_name(i2c, "rtc@43", &dev2));
+	ut_asserteq_ptr(dev, dev2);
+	ut_assertok(device_find_child_by_name(i2c, "rtc@61", &dev2));
+	ut_asserteq_str("rtc@61", dev2->name);
+
+	ut_assertok(device_find_first_child_by_uclass(i2c, UCLASS_I2C_EEPROM,
+						      &dev));
+	ut_asserteq_str("eeprom@2c", dev->name);
+	ut_assertok(device_find_child_by_name(i2c, "eeprom@2c", &dev2));
+	ut_asserteq_ptr(dev, dev2);
+
+	ut_asserteq(-ENODEV, device_find_first_child_by_uclass(i2c,
+							UCLASS_VIDEO, &dev));
+	ut_asserteq(-ENODEV, device_find_child_by_name(i2c, "missing", &dev));
+
+	return 0;
+}
+DM_TEST(dm_test_first_child, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT);