[RFC v1 4/4] kho: Remove notifier system infrastructure

[Jason Miu <jasonmiu@google.com>]

Remove the KHO notifier system.

Eliminate the core KHO notifier API
functions (`register_kho_notifier`, `unregister_kho_notifier`), the
`kho_event` enum, and the notifier chain head from KHO internal
structures.

This infrastructure was used to support the now-removed finalize and
abort states and is no longer required. Client subsystems now interact
with KHO through direct API calls.

Signed-off-by: Jason Miu <jasonmiu@google.com>
---
 include/linux/kexec_handover.h | 20 --------------------
 kernel/kexec_handover.c        | 15 ---------------
 2 files changed, 35 deletions(-)

diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index e29dcf53de7e..09e8f0b0fcab 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -10,14 +10,7 @@ struct kho_scratch {
 	phys_addr_t size;
 };
 
-/* KHO Notifier index */
-enum kho_event {
-	KEXEC_KHO_FINALIZE = 0,
-	KEXEC_KHO_ABORT = 1,
-};
-
 struct folio;
-struct notifier_block;
 
 #ifdef CONFIG_KEXEC_HANDOVER
 bool kho_is_enabled(void);
@@ -28,9 +21,6 @@ struct folio *kho_restore_folio(phys_addr_t phys);
 int kho_add_subtree(const char *name, void *fdt);
 int kho_retrieve_subtree(const char *name, phys_addr_t *phys);
 
-int register_kho_notifier(struct notifier_block *nb);
-int unregister_kho_notifier(struct notifier_block *nb);
-
 void kho_memory_init(void);
 
 void kho_populate(phys_addr_t fdt_phys, u64 fdt_len, phys_addr_t scratch_phys,
@@ -66,16 +56,6 @@ static inline int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
 	return -EOPNOTSUPP;
 }
 
-static inline int register_kho_notifier(struct notifier_block *nb)
-{
-	return -EOPNOTSUPP;
-}
-
-static inline int unregister_kho_notifier(struct notifier_block *nb)
-{
-	return -EOPNOTSUPP;
-}
-
 static inline void kho_memory_init(void)
 {
 }
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index f7933b434364..62f654b08c74 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -16,7 +16,6 @@
 #include <linux/libfdt.h>
 #include <linux/list.h>
 #include <linux/memblock.h>
-#include <linux/notifier.h>
 #include <linux/page-isolation.h>
 
 #include <asm/early_ioremap.h>
@@ -683,13 +682,11 @@ static int kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
 }
 
 struct kho_out {
-	struct blocking_notifier_head chain_head;
 	struct dentry *dir;
 	struct kho_serialization ser;
 };
 
 static struct kho_out kho_out = {
-	.chain_head = BLOCKING_NOTIFIER_INIT(kho_out.chain_head),
 	.ser = {
 		.fdt_list = LIST_HEAD_INIT(kho_out.ser.fdt_list),
 	},
@@ -727,18 +724,6 @@ int kho_add_subtree(const char *name, void *fdt)
 }
 EXPORT_SYMBOL_GPL(kho_add_subtree);
 
-int register_kho_notifier(struct notifier_block *nb)
-{
-	return blocking_notifier_chain_register(&kho_out.chain_head, nb);
-}
-EXPORT_SYMBOL_GPL(register_kho_notifier);
-
-int unregister_kho_notifier(struct notifier_block *nb)
-{
-	return blocking_notifier_chain_unregister(&kho_out.chain_head, nb);
-}
-EXPORT_SYMBOL_GPL(unregister_kho_notifier);
-
 /**
  * kho_preserve_folio - preserve a folio across kexec.
  * @folio: folio to preserve.
-- 
2.51.0.384.g4c02a37b29-goog