Re: [PATCH v4] kernel.h: add comments for system_states

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 03 Sep 2025, Randy Dunlap <rdunlap@infradead.org> wrote:
> 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.

The simple workaround is to separate the enum type and the variable:

/**
 * kernel-doc for the enum
 */
enum system_states {
	...
};

/**
 * kernel-doc for the variable
 */
extern enum system_states system_state;

BR,
Jani.

>
> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> Acked-by: Rafael J. Wysocki <rafael@kernel.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@linux-foundation.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: Len Brown <len.brown@intel.com>
> Cc: linux-pm@vger.kernel.org
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: linux-doc@vger.kernel.org
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.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
>  ------------------------
>

-- 
Jani Nikula, Intel