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

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Message-ID: <20250905140104.42418fba@foz.lan>
Date: Fri, 5 Sep 2025 14:11:43 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: Jani Nikula <jani.nikula@...ux.intel.com>
Cc: Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.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: Re: [PATCH v4] kernel.h: add comments for system_states

Em Fri, 05 Sep 2025 12:02:37 +0300
Jani Nikula <jani.nikula@...ux.intel.com> escreveu:

> On Wed, 03 Sep 2025, Randy Dunlap <rdunlap@...radead.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@...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
> >  ------------------------
> >  
> 

If the problem is with "extern" before enum, fixing kdoc be
fairly trivial.

If you see:

	def dump_function(self, ln, prototype):
	
     	# Prefixes that would be removed
        sub_prefixes = [
	    ...
	    (r"^extern +", "", 0),	
	    ...
	}

        for search, sub, flags in sub_prefixes:
            prototype = KernRe(search, flags).sub(sub, prototype)


we need something similar to that at:
	def dump_enum(self, ln, proto):

alternatively, we could use a simpler approach modifying adding a
non-group optional match for "extern". E.g:

-	r = KernRe(r'enum\s+(\w*)\s*\{(.*)\}')
+       r = KernRe(r'(?:extern\s+)?enum\s+(\w*)\s*\{(.*)\}')

(untested)

Regards,
Mauro


Thanks,
Mauro