linux-kernel - [PATCH v4] kernel.h: add comments for system

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Message-ID: <20250904063631.2364995-1-rdunlap@infradead.org>
Date: Wed,  3 Sep 2025 23:36:31 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: linux-kernel@...r.kernel.org
Cc: Randy Dunlap <rdunlap@...radead.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Pavel Machek <pavel@....cz>,
	Len Brown <len.brown@...el.com>,
	linux-pm@...r.kernel.org,
	Jonathan Corbet <corbet@....net>,
	linux-doc@...r.kernel.org,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
Subject: [PATCH v4] kernel.h: add comments for system_states

Provide some basic comments about the system_states and what they imply.
Also convert the comments to kernel-doc format.

However, kernel-doc does not support kernel-doc notation on extern
struct/union/typedef/enum/etc. So I made this a DOC: block so that
I can use (insert) it into a Documentation (.rst) file and have it
look decent.

Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
Acked-by: Rafael J. Wysocki <rafael@...nel.org> # v1
---
v2: add Rafael's Ack.
v3: add Andrew
v4: add DOC: so that this DOC: block can be used in Documentation/
    add Greg K-H
    add Jon Corbet, Mauro Chehab, & linux-doc

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Pavel Machek <pavel@....cz>
Cc: Len Brown <len.brown@...el.com>
Cc: linux-pm@...r.kernel.org
Cc: Jonathan Corbet <corbet@....net>
Cc: linux-doc@...r.kernel.org
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
---
 Documentation/driver-api/pm/devices.rst |    8 ++++++++
 include/linux/kernel.h                  |   18 ++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

--- linux-next-20250819.orig/include/linux/kernel.h
+++ linux-next-20250819/include/linux/kernel.h
@@ -164,8 +164,22 @@ extern int root_mountflags;
 
 extern bool early_boot_irqs_disabled;
 
-/*
- * Values used for system_state. Ordering of the states must not be changed
+/**
+ * DOC: General system_states available for drivers
+ *
+ * enum system_states - Values used for system_state.
+ *
+ * * @SYSTEM_BOOTING:	%0, no init needed
+ * * @SYSTEM_SCHEDULING:	system is ready for scheduling; OK to use RCU
+ * * @SYSTEM_FREEING_INITMEM: system is freeing all of initmem; almost running
+ * * @SYSTEM_RUNNING:	system is up and running
+ * * @SYSTEM_HALT:	system entered clean system halt state
+ * * @SYSTEM_POWER_OFF:	system entered shutdown/clean power off state
+ * * @SYSTEM_RESTART:	system entered emergency power off or normal restart
+ * * @SYSTEM_SUSPEND:	system entered suspend or hibernate state
+ *
+ * Note:
+ * Ordering of the states must not be changed
  * as code checks for <, <=, >, >= STATE.
  */
 extern enum system_states {
--- linux-next-20250819.orig/Documentation/driver-api/pm/devices.rst
+++ linux-next-20250819/Documentation/driver-api/pm/devices.rst
@@ -241,6 +241,14 @@ before reactivating its class I/O queues
 More power-aware drivers might prepare the devices for triggering system wakeup
 events.
 
+System states available for drivers
+-----------------------------------
+
+These system states are available for drivers to help them determine how to
+handle state transitions.
+
+.. kernel-doc:: include/linux/kernel.h
+   :doc: General system_states available for drivers
 
 Call Sequence Guarantees
 ------------------------