Merge branch '2022-03-09-events-subsystem' into next

To quote the author:
It is a common need in U-Boot to have one subsystem notify another
when something happens. An example is reading a partition table when a
new block device is set up.

It is also common to add weak functions and 'hook' functions to modify
how U-Boot works. See for example ft_board_setup() and the like.

U-Boot would benefit from a generic mechanism to handle these cases,
with the ability to hook into various 'events' in a
subsystem-independent and transparent way.

This series provides a way to create and dispatch events, with a way of
registering a 'spy' which watches for events of different types. This
allows 'hook' functions to be created in a generic way.

It also includes a script to list the hooks in an image, which is a bit
easier to debug than weak functions, as well as an 'event' command to
do the same from within U-Boot.

These 'static' events can be used to replace hooks like misc_init_f(),
for example. Also included is basic support for 'dynamic' events, where
a spy can be registered at runtime. The need for this is still being
figured out.

4 files changed, 32 insertions, 0 deletions

diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig
index 8f7703c8b58..5c3400417f9 100644
--- a/drivers/core/Kconfig
+++ b/drivers/core/Kconfig
@@ -77,6 +77,16 @@ config DM_DEVICE_REMOVE
 	  it causes unplugged devices to linger around in the dm-tree, and it
 	  causes USB host controllers to not be stopped when booting the OS.
 
+config DM_EVENT
+	bool "Support events with driver model"
+	depends on DM
+	imply EVENT
+	default y if SANDBOX
+	help
+	  This enables support for generating events related to driver model
+	  operations, such as prbing or removing a device. Subsystems can
+	  register a 'spy' function that is called when the event occurs.
+
 config SPL_DM_DEVICE_REMOVE
 	bool "Support device removal in SPL"
 	depends on SPL_DM
diff --git a/drivers/core/device-remove.c b/drivers/core/device-remove.c
index e6ec6ff4212..73d2e9e4208 100644
--- a/drivers/core/device-remove.c
+++ b/drivers/core/device-remove.c
@@ -207,6 +207,10 @@ int device_remove(struct udevice *dev, uint flags)
 	if (!(dev_get_flags(dev) & DM_FLAG_ACTIVATED))
 		return 0;
 
+	ret = device_notify(dev, EVT_DM_PRE_REMOVE);
+	if (ret)
+		return ret;
+
 	/*
 	 * If the child returns EKEYREJECTED, continue. It just means that it
 	 * didn't match the flags.
@@ -256,6 +260,10 @@ int device_remove(struct udevice *dev, uint flags)
 
 	dev_bic_flags(dev, DM_FLAG_ACTIVATED);
 
+	ret = device_notify(dev, EVT_DM_POST_REMOVE);
+	if (ret)
+		goto err_remove;
+
 	return 0;
 
 err_remove:
diff --git a/drivers/core/device.c b/drivers/core/device.c
index 901c1e2f7db..1b356f12dd8 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -10,6 +10,7 @@
 
 #include <common.h>
 #include <cpu_func.h>
+#include <event.h>
 #include <log.h>
 #include <asm/global_data.h>
 #include <asm/io.h>
@@ -493,6 +494,10 @@ int device_probe(struct udevice *dev)
 	if (dev_get_flags(dev) & DM_FLAG_ACTIVATED)
 		return 0;
 
+	ret = device_notify(dev, EVT_DM_PRE_PROBE);
+	if (ret)
+		return ret;
+
 	drv = dev->driver;
 	assert(drv);
 
@@ -597,6 +602,10 @@ int device_probe(struct udevice *dev)
 				  dev->name, ret, errno_str(ret));
 	}
 
+	ret = device_notify(dev, EVT_DM_POST_PROBE);
+	if (ret)
+		return ret;
+
 	return 0;
 fail_uclass:
 	if (device_remove(dev, DM_REMOVE_NORMAL)) {
diff --git a/drivers/core/root.c b/drivers/core/root.c
index e3f87956d86..8efb4256b27 100644
--- a/drivers/core/root.c
+++ b/drivers/core/root.c
@@ -404,6 +404,11 @@ int dm_init_and_scan(bool pre_reloc_only)
 			return ret;
 		}
 	}
+	if (CONFIG_IS_ENABLED(DM_EVENT)) {
+		ret = event_notify_null(EVT_DM_POST_INIT);
+		if (ret)
+			return log_msg_ret("ev", ret);
+	}
 
 	return 0;
 }