dm: core: Allow parents to pass data to children during probe

Buses sometimes want to pass data to their children when they are probed.
For example, a SPI bus may want to tell the slave device about the chip
select it is connected to.

Add a new function to permit the parent data to be supplied to the child.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>

include/dm/device-internal.h

@@ -65,6 +65,19 @@ int device_bind_by_name(struct udevice *parent, bool pre_reloc_only,
  */
 int device_probe(struct udevice *dev);
 
+/**
+ * device_probe() - Probe a child device, activating it
+ *
+ * Activate a device so that it is ready for use. All its parents are probed
+ * first. The child is provided with parent data if parent_priv is not NULL.
+ *
+ * @dev: Pointer to device to probe
+ * @parent_priv: Pointer to parent data. If non-NULL then this is provided to
+ * the child.
+ * @return 0 if OK, -ve on error
+ */
+int device_probe_child(struct udevice *dev, void *parent_priv);
+
 /**
  * device_remove() - Remove a device, de-activating it
  *

include/dm/device.h

@@ -139,6 +139,10 @@ struct udevice_id {
  * @per_child_auto_alloc_size: Each device can hold private data owned by
  * its parent. If required this will be automatically allocated if this
  * value is non-zero.
+ * TODO(sjg@chromium.org): I'm considering dropping this, and just having
+ * device_probe_child() pass it in. So far the use case for allocating it
+ * is SPI, but I found that unsatisfactory. Since it is here I will leave it
+ * until things are clearer.
  * @ops: Driver-specific operations. This is typically a list of function
  * pointers defined by the driver, to implement driver functions required by
  * the uclass.