[PATCH v2 05/13] event: Add basic support for events
Simon Glass
sjg at chromium.org
Fri Mar 4 16:43:00 CET 2022
Add a way to create and dispatch events without needing to allocate
memory. Also add a way to 'spy' on events, thus allowing 'hooks' to be
created.
Use a linker list for static events, which we can use to replace functions
like arch_cpu_init_f(). Allow an EVENT_DEBUG option which makes it
easier to see what is going on at runtime, but uses more code space.
Dynamic events allow the creation of a spy at runtime. This is not always
necessary, but can be enabled with EVENT_DYNAMIC if needed.
A 'test' event is the only option for now.
Signed-off-by: Simon Glass <sjg at chromium.org>
---
Changes in v2:
- Add a 'used' attribute to avoid LTO dropping the code
MAINTAINERS | 6 +
common/Kconfig | 31 +++++
common/Makefile | 2 +
common/board_r.c | 1 +
common/event.c | 186 +++++++++++++++++++++++++++++
common/log.c | 1 +
include/asm-generic/global_data.h | 13 +++
include/event.h | 188 ++++++++++++++++++++++++++++++
include/event_internal.h | 35 ++++++
include/log.h | 2 +
10 files changed, 465 insertions(+)
create mode 100644 common/event.c
create mode 100644 include/event.h
create mode 100644 include/event_internal.h
diff --git a/MAINTAINERS b/MAINTAINERS
index fb171e0c68..b534ad66b9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -809,6 +809,12 @@ S: Maintained
F: doc/usage/environment.rst
F: scripts/env2string.awk
+EVENTS
+M: Simon Glass <sjg at chromium.org>
+S: Maintained
+F: common/event.c
+F: include/event.h
+
FASTBOOT
S: Orphaned
F: cmd/fastboot.c
diff --git a/common/Kconfig b/common/Kconfig
index 82cd864baf..76c04b2001 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -492,6 +492,37 @@ config DISPLAY_BOARDINFO_LATE
menu "Start-up hooks"
+config EVENT
+ bool "General-purpose event-handling mechanism"
+ default y if SANDBOX
+ help
+ This enables sending and processing of events, to allow interested
+ parties to be alerted when something happens. This is an attempt to
+ step the flow of weak functions, hooks, functions in board_f.c
+ and board_r.c and the Kconfig options below.
+
+ See doc/develop/event.rst for more information.
+
+if EVENT
+
+config EVENT_DYNAMIC
+ bool "Support event registration at runtime"
+ default y if SANDBOX
+ help
+ Enable this to support adding an event spy at runtime, without adding
+ it to the EVENT_SPy() linker list. This increases code size slightly
+ but provides more flexibility for boards and subsystems that need it.
+
+config EVENT_DEBUG
+ bool "Enable event debugging assistance"
+ default y if SANDBOX
+ help
+ Enable this get usefui features for seeing what is happening with
+ events, such as event-type names. This adds to the code size of
+ U-Boot so can be turned off for production builds.
+
+endif # EVENT
+
config ARCH_EARLY_INIT_R
bool "Call arch-specific init soon after relocation"
help
diff --git a/common/Makefile b/common/Makefile
index 3eff719601..cc2ba30c63 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -89,6 +89,8 @@ obj-y += malloc_simple.o
endif
endif
+obj-$(CONFIG_$(SPL_TPL_)EVENT) += event.o
+
obj-$(CONFIG_$(SPL_TPL_)HASH) += hash.o
obj-$(CONFIG_IO_TRACE) += iotrace.o
obj-y += memsize.o
diff --git a/common/board_r.c b/common/board_r.c
index c24d9b4e22..b92c1bb0be 100644
--- a/common/board_r.c
+++ b/common/board_r.c
@@ -594,6 +594,7 @@ static int run_main_loop(void)
static init_fnc_t init_sequence_r[] = {
initr_trace,
initr_reloc,
+ event_init,
/* TODO: could x86/PPC have this also perhaps? */
#if defined(CONFIG_ARM) || defined(CONFIG_RISCV)
initr_caches,
diff --git a/common/event.c b/common/event.c
new file mode 100644
index 0000000000..366be24569
--- /dev/null
+++ b/common/event.c
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Events provide a general-purpose way to react to / subscribe to changes
+ * within U-Boot
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg at chromium.org>
+ */
+
+#define LOG_CATEGORY LOGC_EVENT
+
+#include <common.h>
+#include <event.h>
+#include <event_internal.h>
+#include <log.h>
+#include <linker_lists.h>
+#include <malloc.h>
+#include <asm/global_data.h>
+#include <linux/list.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#if CONFIG_IS_ENABLED(EVENT_DEBUG)
+const char *const type_name[] = {
+ "none",
+ "test",
+};
+
+_Static_assert(ARRAY_SIZE(type_name) == EVT_COUNT, "event type_name size");
+#endif
+
+static const char *event_type_name(enum event_t type)
+{
+#if CONFIG_IS_ENABLED(EVENT_DEBUG)
+ return type_name[type];
+#else
+ return "(unknown)";
+#endif
+}
+
+static int notify_static(struct event *ev)
+{
+ struct evspy_info *start =
+ ll_entry_start(struct evspy_info, evspy_info);
+ const int n_ents = ll_entry_count(struct evspy_info, evspy_info);
+ struct evspy_info *spy;
+
+ for (spy = start; spy != start + n_ents; spy++) {
+ if (spy->type == ev->type) {
+ int ret;
+
+ log_debug("Sending event %x/%s to spy '%s'\n", ev->type,
+ event_type_name(ev->type), event_spy_id(spy));
+ ret = spy->func(NULL, ev);
+
+ /*
+ * TODO: Handle various return codes to
+ *
+ * - claim an event (no others will see it)
+ * - return an error from the event
+ */
+ if (ret)
+ return log_msg_ret("spy", ret);
+ }
+ }
+
+ return 0;
+}
+
+static int notify_dynamic(struct event *ev)
+{
+ struct event_state *state = gd_event_state();
+ struct event_spy *spy, *next;
+
+ list_for_each_entry_safe(spy, next, &state->spy_head, sibling_node) {
+ if (spy->type == ev->type) {
+ int ret;
+
+ log_debug("Sending event %x/%s to spy '%s'\n", ev->type,
+ event_type_name(ev->type), spy->id);
+ ret = spy->func(spy->ctx, ev);
+
+ /*
+ * TODO: Handle various return codes to
+ *
+ * - claim an event (no others will see it)
+ * - return an error from the event
+ */
+ if (ret)
+ return log_msg_ret("spy", ret);
+ }
+ }
+
+ return 0;
+}
+
+int event_notify(enum event_t type, void *data, int size)
+{
+ struct event event;
+ int ret;
+
+ event.type = type;
+ if (size > sizeof(event.data))
+ return log_msg_ret("size", -E2BIG);
+ memcpy(&event.data, data, size);
+
+ ret = notify_static(&event);
+ if (ret)
+ return log_msg_ret("dyn", ret);
+
+ if (CONFIG_IS_ENABLED(EVENT_DYNAMIC)) {
+ ret = notify_dynamic(&event);
+ if (ret)
+ return log_msg_ret("dyn", ret);
+ }
+
+ return 0;
+}
+
+int event_notify_null(enum event_t type)
+{
+ return event_notify(type, NULL, 0);
+}
+
+void event_show_spy_list(void)
+{
+ struct evspy_info *start =
+ ll_entry_start(struct evspy_info, evspy_info);
+ const int n_ents = ll_entry_count(struct evspy_info, evspy_info);
+ struct evspy_info *spy;
+ const int size = sizeof(ulong) * 2;
+
+ printf("Seq %-24s %*s %s\n", "Type", size, "Function", "ID");
+ for (spy = start; spy != start + n_ents; spy++) {
+ printf("%3x %-3x %-20s %*p %s\n", (uint)(spy - start),
+ spy->type, event_type_name(spy->type), size, spy->func,
+ event_spy_id(spy));
+ }
+}
+
+#if CONFIG_IS_ENABLED(EVENT_DYNAMIC)
+static void spy_free(struct event_spy *spy)
+{
+ list_del(&spy->sibling_node);
+}
+
+int event_register(const char *id, enum event_t type, event_handler_t func, void *ctx)
+{
+ struct event_state *state = gd_event_state();
+ struct event_spy *spy;
+
+ if (!CONFIG_IS_ENABLED(EVENT_DYNAMIC))
+ return -ENOSYS;
+ spy = malloc(sizeof(*spy));
+ if (!spy)
+ return log_msg_ret("alloc", -ENOMEM);
+
+ spy->id = id;
+ spy->type = type;
+ spy->func = func;
+ spy->ctx = ctx;
+ list_add_tail(&spy->sibling_node, &state->spy_head);
+
+ return 0;
+}
+
+int event_uninit(void)
+{
+ struct event_state *state = gd_event_state();
+ struct event_spy *spy, *next;
+
+ list_for_each_entry_safe(spy, next, &state->spy_head, sibling_node)
+ spy_free(spy);
+
+ return 0;
+}
+
+int event_init(void)
+{
+ struct event_state *state = gd_event_state();
+
+ INIT_LIST_HEAD(&state->spy_head);
+
+ return 0;
+}
+#endif /* EVENT_DYNAMIC */
diff --git a/common/log.c b/common/log.c
index f7e0c0fbf5..7254aa70bf 100644
--- a/common/log.c
+++ b/common/log.c
@@ -28,6 +28,7 @@ static const char *const log_cat_name[] = {
"devres",
"acpi",
"boot",
+ "event",
};
_Static_assert(ARRAY_SIZE(log_cat_name) == LOGC_COUNT - LOGC_NONE,
diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index c2f8fad1cb..e49f5bf2f7 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -20,6 +20,7 @@
*/
#ifndef __ASSEMBLY__
+#include <event_internal.h>
#include <fdtdec.h>
#include <membuff.h>
#include <linux/list.h>
@@ -467,6 +468,12 @@ struct global_data {
*/
char *smbios_version;
#endif
+#if CONFIG_IS_ENABLED(EVENT)
+ /**
+ * @event_state: Points to the current state of events
+ */
+ struct event_state event_state;
+#endif
};
#ifndef DO_DEPS_ONLY
static_assert(sizeof(struct global_data) == GD_SIZE);
@@ -532,6 +539,12 @@ static_assert(sizeof(struct global_data) == GD_SIZE);
#define gd_set_multi_dtb_fit(_dtb)
#endif
+#if CONFIG_IS_ENABLED(EVENT_DYNAMIC)
+#define gd_event_state() ((struct event_state *)&gd->event_state)
+#else
+#define gd_event_state() NULL
+#endif
+
/**
* enum gd_flags - global data flags
*
diff --git a/include/event.h b/include/event.h
new file mode 100644
index 0000000000..effd58c704
--- /dev/null
+++ b/include/event.h
@@ -0,0 +1,188 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Events provide a general-purpose way to react to / subscribe to changes
+ * within U-Boot
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg at chromium.org>
+ */
+
+#ifndef __event_h
+#define __event_h
+
+/**
+ * enum event_t - Types of events supported by U-Boot
+ *
+ * @EVT_DM_PRE_PROBE: Device is about to be probed
+ */
+enum event_t {
+ EVT_NONE,
+ EVT_TEST,
+
+ EVT_COUNT
+};
+
+union event_data {
+ /**
+ * struct event_data_test - test data
+ *
+ * @signal: A value to update the state with
+ */
+ struct event_data_test {
+ int signal;
+ } test;
+};
+
+/**
+ * struct event - an event that can be sent and received
+ *
+ * @type: Event type
+ * @data: Data for this particular event
+ */
+struct event {
+ enum event_t type;
+ union event_data data;
+};
+
+/** Function type for event handlers */
+typedef int (*event_handler_t)(void *ctx, struct event *event);
+
+/**
+ * struct evspy_info - information about an event spy
+ *
+ * @func: Function to call when the event is activated (must be first)
+ * @type: Event type
+ * @id: Event id string
+ */
+struct evspy_info {
+ event_handler_t func;
+ enum event_t type;
+#if CONFIG_IS_ENABLED(EVENT_DEBUG)
+ const char *id;
+#endif
+};
+
+/* Declare a new event spy */
+#if CONFIG_IS_ENABLED(EVENT_DEBUG)
+#define _ESPY_REC(_type, _func) { _func, _type, #_func, }
+#else
+#define _ESPY_REC(_type, _func) { _func, _type, }
+#endif
+
+static inline const char *event_spy_id(struct evspy_info *spy)
+{
+#if CONFIG_IS_ENABLED(EVENT_DEBUG)
+ return spy->id;
+#else
+ return "?";
+#endif
+}
+
+/*
+ * It seems that LTO will drop list entries if it decides they are not used,
+ * although the conditions that cause this are unclear.
+ *
+ * The example found is the following:
+ *
+ * static int sandbox_misc_init_f(void *ctx, struct event *event)
+ * {
+ * return sandbox_early_getopt_check();
+ * }
+ * EVENT_SPY(EVT_MISC_INIT_F, sandbox_misc_init_f);
+ *
+ * where EVENT_SPY uses ll_entry_declare()
+ *
+ * In this case, LTO decides to drop the sandbox_misc_init_f() function
+ * (which is fine) but then drops the linker-list entry too. This means
+ * that the code no longer works, in this case sandbox no-longer checks its
+ * command-line arguments properly.
+ *
+ * Without LTO, the KEEP() command in the .lds file is enough to keep the
+ * entry around. But with LTO it seems that the entry has already been
+ * dropped before the link script is considered.
+ *
+ * The only solution I can think of is to mark linker-list entries as 'used'
+ * using an attribute. This should be safe, since we don't actually want to drop
+ * any of these. However this does slightly limit LTO's optimisation choices.
+ */
+#define EVENT_SPY(_type, _func) \
+ static __attribute__((used)) ll_entry_declare(struct evspy_info, \
+ _type, evspy_info) = \
+ _ESPY_REC(_type, _func)
+
+/**
+ * event_register - register a new spy
+ *
+ * @id: Spy ID
+ * @type: Event type to subscribe to
+ * @func: Function to call when the event is sent
+ * @ctx: Context to pass to the function
+ * @return 0 if OK, -ve on error
+ */
+int event_register(const char *id, enum event_t type, event_handler_t func,
+ void *ctx);
+
+#if CONFIG_IS_ENABLED(EVENT)
+/**
+ * event_notify() - notify spies about an event
+ *
+ * It is possible to pass in union event_data here but that may not be
+ * convenient if the data is elsewhere, or is one of the members of the union.
+ * So this uses a void * for @data, with a separate @size.
+ *
+ * @type: Event type
+ * @data: Event data to be sent (e.g. union_event_data)
+ * @size: Size of data in bytes
+ * @return 0 if OK, -ve on error
+ */
+int event_notify(enum event_t type, void *data, int size);
+
+/**
+ * event_notify_null() - notify spies about an event
+ *
+ * Data is NULL and the size is 0
+ *
+ * @type: Event type
+ * @return 0 if OK, -ve on error
+ */
+int event_notify_null(enum event_t type);
+#else
+static inline int event_notify(enum event_t type, void *data, int size)
+{
+ return 0;
+}
+
+static inline int event_notify_null(enum event_t type)
+{
+ return 0;
+}
+#endif
+
+#if CONFIG_IS_ENABLED(EVENT_DYNAMIC)
+/**
+ * event_uninit() - Clean up dynamic events
+ *
+ * This removes all dynamic event handlers
+ */
+int event_uninit(void);
+
+/**
+ * event_uninit() - Set up dynamic events
+ *
+ * Init a list of dynamic event handlers, so that these can be added as
+ * needed
+ */
+int event_init(void);
+#else
+static inline int event_uninit(void)
+{
+ return 0;
+}
+
+static inline int event_init(void)
+{
+ return 0;
+}
+#endif
+
+#endif
diff --git a/include/event_internal.h b/include/event_internal.h
new file mode 100644
index 0000000000..8432c6f0e5
--- /dev/null
+++ b/include/event_internal.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Internal definitions for events
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg at chromium.org>
+ */
+
+#ifndef __event_internal_h
+#define __event_internal_h
+
+#include <event.h>
+#include <linux/list.h>
+
+/**
+ * struct event_spy - a spy that watches for an event of a particular type
+ *
+ * @id: Spy ID
+ * @type: Event type to subscribe to
+ * @func: Function to call when the event is sent
+ * @ctx: Context to pass to the function
+ */
+struct event_spy {
+ struct list_head sibling_node;
+ const char *id;
+ enum event_t type;
+ event_handler_t func;
+ void *ctx;
+};
+
+struct event_state {
+ struct list_head spy_head;
+};
+
+#endif
diff --git a/include/log.h b/include/log.h
index ce48d51446..8f35c10abb 100644
--- a/include/log.h
+++ b/include/log.h
@@ -98,6 +98,8 @@ enum log_category_t {
LOGC_ACPI,
/** @LOGC_BOOT: Related to boot process / boot image processing */
LOGC_BOOT,
+ /** @LOGC_EVENT: Related to event and event handling */
+ LOGC_EVENT,
/** @LOGC_COUNT: Number of log categories */
LOGC_COUNT,
/** @LOGC_END: Sentinel value for lists of log categories */
--
2.35.1.616.g0bdcbb4464-goog
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