boot: Add UCLASS support for extension boards

Introduce UCLASS-based extension board support to enable more
standardized and automatic loading of extension board device tree
overlays in preparation for integration with bootstd and pxe_utils.

Several #if CONFIG_IS_ENABLED are used in cmd/extension_board.c to ease the
development but don't worry they are removed later in the series.

Signed-off-by: Kory Maincent (TI.com) <[email protected]>
Reviewed-by: Simon Glass <[email protected]>

2 files changed, 72 insertions, 0 deletions

diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 6be59093160..eb6416b5917 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -63,6 +63,7 @@ enum uclass_id {
 	UCLASS_ETH,		/* Ethernet device */
 	UCLASS_ETH_PHY,		/* Ethernet PHY device */
 	UCLASS_EXTCON,		/* External Connector Class */
+	UCLASS_EXTENSION,	/* Extension board */
 	UCLASS_FFA,		/* Arm Firmware Framework for Armv8-A */
 	UCLASS_FFA_EMUL,		/* sandbox FF-A device emulator */
 	UCLASS_FIRMWARE,	/* Firmware */
diff --git a/include/extension_board.h b/include/extension_board.h
index 0821dddd8ff..a74a9c67c01 100644
--- a/include/extension_board.h
+++ b/include/extension_board.h
@@ -7,11 +7,56 @@
 #ifndef __EXTENSION_SUPPORT_H
 #define __EXTENSION_SUPPORT_H
 
+#include <alist.h>
+#include <dm/device.h>
 #include <linux/list.h>
+#include <dm/platdata.h>
 
 extern struct list_head extension_list;
 
 /**
+ * dm_extension_get_list - Get the extension list
+ * Return: The extension alist pointer, or NULL if no such list exists.
+ *
+ * The caller must not free the list.
+ */
+struct alist *dm_extension_get_list(void);
+
+/**
+ * dm_extension_probe - Probe extension device
+ * @dev: Extension device that needs to be probed
+ * Return: Zero on success, negative on failure.
+ */
+int dm_extension_probe(struct udevice *dev);
+
+/**
+ * dm_extension_remove - Remove extension device
+ * @dev: Extension device that needs to be removed
+ * Return: Zero on success, negative on failure.
+ */
+int dm_extension_remove(struct udevice *dev);
+
+/**
+ * dm_extension_scan - Scan extension boards available.
+ * Return: Zero on success, negative on failure.
+ */
+int dm_extension_scan(void);
+
+/**
+ * dm_extension_apply - Apply extension board overlay to the devicetree
+ * @extension_num: Extension number to be applied
+ * Return: Zero on success, negative on failure.
+ */
+int dm_extension_apply(int extension_num);
+
+/**
+ * dm_extension_apply_all - Apply all extension board overlays to the
+ *			    devicetree
+ * Return: Zero on success, negative on failure.
+ */
+int dm_extension_apply_all(void);
+
+/**
  * extension - Description fields of an extension board
  * @list: List head
  * @name: Name of the extension
@@ -29,6 +74,32 @@ struct extension {
 	char other[32];
 };
 
+struct extension_ops {
+	/**
+	 * scan - Add system-specific function to scan extension boards.
+	 * @dev: extension device
+	 * @extension_list: alist of extension to expand
+	 * Return: The number of extension or a negative value in case of
+	 *	   error.
+	 */
+	int (*scan)(struct udevice *dev, struct alist *extension_list);
+};
+
+#define extension_get_ops(dev)  ((struct extension_ops *)(dev)->driver->ops)
+
+/* Currently, only one extension driver enabled at a time is supported */
+#define U_BOOT_EXTENSION(_name, _scan_func) \
+	U_BOOT_DRIVER(_name) = { \
+		.name = #_name, \
+		.id = UCLASS_EXTENSION, \
+		.probe = dm_extension_probe, \
+		.remove = dm_extension_remove, \
+		.ops = &(struct extension_ops) { \
+		       .scan = _scan_func, \
+		       }, \
+		.priv_auto = sizeof(struct alist), \
+	}
+
 /**
  * extension_board_scan - Add system-specific function to scan extension board.
  * @param extension_list	List of extension board information to update.