ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/thread-device.c b/drivers/md/dm-vdo/thread-device.c
new file mode 100644
index 000000000..df13ca914
--- /dev/null
+++ b/drivers/md/dm-vdo/thread-device.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "thread-device.h"
+
+/* A registry of threads associated with device id numbers. */
+static struct thread_registry device_id_thread_registry;
+
+/* Any registered thread must be unregistered. */
+void vdo_register_thread_device_id(struct registered_thread *new_thread,
+				   unsigned int *id_ptr)
+{
+	vdo_register_thread(&device_id_thread_registry, new_thread, id_ptr);
+}
+
+void vdo_unregister_thread_device_id(void)
+{
+	vdo_unregister_thread(&device_id_thread_registry);
+}
+
+int vdo_get_thread_device_id(void)
+{
+	const unsigned int *pointer;
+
+	pointer = vdo_lookup_thread(&device_id_thread_registry);
+	return (pointer != NULL) ? *pointer : -1;
+}
+
+void vdo_initialize_thread_device_registry(void)
+{
+	vdo_initialize_thread_registry(&device_id_thread_registry);
+}