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.

3 files changed, 36 insertions, 0 deletions

diff --git a/cmd/Kconfig b/cmd/Kconfig
index d10deed244b..1ed63fa06c1 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -2367,6 +2367,14 @@ config CMD_DIAG
 	  available tests and running either all the tests, or specific tests
 	  identified by name.
 
+config CMD_EVENT
+	bool "event - Show information about events"
+	default y if EVENT_DEBUG
+	help
+	  This enables the 'event' command which provides information about
+	  events and event-handler routines. This can help to device event
+	  hadling.
+
 config CMD_IRQ
 	bool "irq - Show information about interrupts"
 	depends on !ARM && !MIPS && !RISCV && !SH
diff --git a/cmd/Makefile b/cmd/Makefile
index 166c652d982..0d2b2ee092d 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_CMD_DIAG) += diag.o
 endif
 obj-$(CONFIG_CMD_ADTIMG) += adtimg.o
 obj-$(CONFIG_CMD_ABOOTIMG) += abootimg.o
+obj-$(CONFIG_CMD_EVENT) += event.o
 obj-$(CONFIG_CMD_EXTENSION) += extension_board.o
 obj-$(CONFIG_CMD_ECHO) += echo.o
 obj-$(CONFIG_ENV_IS_IN_EEPROM) += eeprom.o
diff --git a/cmd/event.c b/cmd/event.c
new file mode 100644
index 00000000000..9cac2023530
--- /dev/null
+++ b/cmd/event.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Command-line access to events
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <[email protected]>
+ */
+
+#include <common.h>
+#include <command.h>
+#include <event.h>
+
+static int do_event_list(struct cmd_tbl *cmdtp, int flag, int argc,
+			 char *const argv[])
+{
+	event_show_spy_list();
+
+	return 0;
+}
+
+#ifdef CONFIG_SYS_LONGHELP
+static char event_help_text[] =
+	"event list   - list event spies";
+#endif
+
+U_BOOT_CMD_WITH_SUBCMDS(event, "Events", event_help_text,
+	U_BOOT_SUBCMD_MKENT(list, 1, 1, do_event_list));