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.

2 files changed, 50 insertions, 0 deletions

diff --git a/doc/usage/event.rst b/doc/usage/event.rst
new file mode 100644
index 00000000000..c0f8acd727b
--- /dev/null
+++ b/doc/usage/event.rst
@@ -0,0 +1,49 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+event command
+=============
+
+Synopsis
+--------
+
+::
+
+    event list
+
+Description
+-----------
+
+The event command provides spy list.
+
+This shows the following information:
+
+Seq
+    Sequence number of the spy, numbered from 0
+
+Type
+    Type of the spy, both as a number and a label. If `CONFIG_EVENT_DEBUG` is
+    not enabled, the label just shows `(unknown)`.
+
+Function
+    Address of the function to call
+
+ID
+    ID string for this event, if `CONFIG_EVENT_DEBUG` is enabled. Otherwise this
+    just shows `?`.
+
+
+See :doc:`../develop/event` for more information on events.
+
+Example
+-------
+
+::
+
+    => event list
+    Seq  Type                              Function  ID
+      0  7   misc_init_f               55a070517c68  ?
+
+Configuration
+-------------
+
+The event command is only available if CONFIG_CMD_EVENT=y.
diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index 0aacf531b22..750102830b5 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -29,6 +29,7 @@ Shell commands
    x86/cbsysinfo
    conitrace
    echo
+   event
    exception
    extension
    exit