dm: core: Add dev_read_enabled() to check if a device is enabled

This function allows a device's status to be read. This indicates whether
the device should be enabled or disabled.

Note: In normal operation disabled devices will not be present in the
driver-model tree.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Tested-on: Beaver, Jetson-TK1

drivers/core/read.c

@@ -138,3 +138,14 @@ const uint8_t *dev_read_u8_array_ptr(struct udevice *dev, const char *propname,
 {
 	return ofnode_read_u8_array_ptr(dev_ofnode(dev), propname, sz);
 }
+
+int dev_read_enabled(struct udevice *dev)
+{
+	ofnode node = dev_ofnode(dev);
+
+	if (ofnode_is_np(node))
+		return of_device_is_available(ofnode_to_np(node));
+	else
+		return fdtdec_get_is_enabled(gd->fdt_blob,
+					     ofnode_to_offset(node));
+}

include/dm/read.h

@@ -315,6 +315,19 @@ ofnode dev_read_next_subnode(ofnode node);
 const uint8_t *dev_read_u8_array_ptr(struct udevice *dev, const char *propname,
 				     size_t sz);
 
+/**
+ * dev_read_enabled() - check whether a node is enabled
+ *
+ * This looks for a 'status' property. If this exists, then returns 1 if
+ * the status is 'ok' and 0 otherwise. If there is no status property,
+ * it returns 1 on the assumption that anything mentioned should be enabled
+ * by default.
+ *
+ * @dev: device to examine
+ * @return integer value 0 (not enabled) or 1 (enabled)
+ */
+int dev_read_enabled(struct udevice *dev);
+
 #else /* CONFIG_DM_DEV_READ_INLINE is enabled */
 
 static inline int dev_read_u32_default(struct udevice *dev,
@@ -432,6 +445,11 @@ static inline const uint8_t *dev_read_u8_array_ptr(struct udevice *dev,
 	return ofnode_read_u8_array_ptr(dev_ofnode(dev), propname, sz);
 }
 
+static inline int dev_read_enabled(struct udevice *dev)
+{
+	return fdtdec_get_is_enabled(gd->fdt_blob, dev_of_offset(dev));
+}
+
 #endif /* CONFIG_DM_DEV_READ_INLINE */
 
 /**