cyclic: make clients embed a struct cyclic_info in their own data structure

There are of course not a whole lot of examples in-tree yet, but
before they appear, let's make this API change: Instead of separately
allocating a 'struct cyclic_info', make the users embed such an
instance in their own structure, and make the convention that the
callback simply receives the 'struct cyclic_info *', from which the
clients can get their own data using the container_of() macro.

This has a number of advantages.

First, it means cyclic_register() simply cannot fail, simplifying the
code. The necessary storage will simply be allocated automatically
when the client's own structure is allocated (often via
uclass_priv_auto or similar).

Second, code for which CONFIG_CYCLIC is just an option can more easily
be written without #ifdefs, if we just provide an empty struct
cyclic_info {}. For example, the nested CONFIG_IS_ENABLED()s in
https://lore.kernel.org/u-boot/20240316201416.211480-1-marek.vasut+renesas@mailbox.org/
are mostly due to the existence of the 'struct cyclic_info *' member
being guarded by #ifdef CONFIG_CYCLIC.

And we do probably want to avoid the extra memory overhead of that
member when !CONFIG_CYCLIC. But that is automatic if, instead of a
'struct cyclic_info *', one simply embeds a 'struct cyclic_info',
which will have size 0 when !CONFIG_CYCLIC. Also, the no-op
cyclic_register() function can just unconditionally be called, and the
compiler will see that (1) the callback is referenced, so not emit a
warning for a maybe-unused function and (2) see that it can actually
never be reached, so not emit any code for it.

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>

1 files changed, 12 insertions, 7 deletions

diff --git a/test/common/cyclic.c b/test/common/cyclic.c
index 461f8cf91f4..51a07c576b6 100644
--- a/test/common/cyclic.c
+++ b/test/common/cyclic.c
@@ -12,22 +12,27 @@
 #include <linux/delay.h>
 
 /* Test that cyclic function is called */
-static bool cyclic_active = false;
+static struct cyclic_test {
+	struct cyclic_info cyclic;
+	bool called;
+} cyclic_test;
 
-static void cyclic_test(void *ctx)
+static void test_cb(struct cyclic_info *c)
 {
-	cyclic_active = true;
+	struct cyclic_test *t = container_of(c, struct cyclic_test, cyclic);
+	t->called = true;
 }
 
 static int dm_test_cyclic_running(struct unit_test_state *uts)
 {
-	cyclic_active = false;
-	ut_assertnonnull(cyclic_register(cyclic_test, 10 * 1000, "cyclic_demo",
-					 NULL));
+	cyclic_test.called = false;
+	cyclic_register(&cyclic_test.cyclic, test_cb, 10 * 1000, "cyclic_test");
 
 	/* Execute all registered cyclic functions */
 	schedule();
-	ut_asserteq(true, cyclic_active);
+	ut_asserteq(true, cyclic_test.called);
+
+	cyclic_unregister(&cyclic_test.cyclic);
 
 	return 0;
 }