linux-kernel - Re: linux-next: build warning after merge of the v4l-dvb tree

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Date:   Mon, 8 Feb 2021 18:40:14 +0100
From:   Mauro Carvalho Chehab <mchehab@...nel.org>
To:     Ezequiel Garcia <ezequiel@...labora.com>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build warning after merge of the v4l-dvb tree

Em Mon, 08 Feb 2021 13:57:56 -0300
Ezequiel Garcia <ezequiel@...labora.com> escreveu:

> On Mon, 2021-02-08 at 18:46 +0200, Sakari Ailus wrote:
> > Hi Ezequiel,
> > 
> > Thanks for addressing this.
> > 
> > On Mon, Feb 08, 2021 at 01:42:21PM -0300, Ezequiel Garcia wrote:  
> > > Hi Stephen,
> > > 
> > > On Mon, 2021-02-08 at 23:37 +1100, Stephen Rothwell wrote:  
> > > > Hi all,
> > > > 
> > > > After merging the v4l-dvb tree, today's linux-next build (htmldocs)
> > > > produced this warning:
> > > > 
> > > > include/media/v4l2-async.h:178: warning: expecting prototype for v4l2_async_notifier_add_fwnode_subdev(). Prototype was for
> > > > __v4l2_async_notifier_add_fwnode_subdev() instead
> > > > include/media/v4l2-async.h:207: warning: expecting prototype for v4l2_async_notifier_add_fwnode_remote_subdev(). Prototype was for
> > > > __v4l2_async_notifier_add_fwnode_remote_subdev() instead
> > > > include/media/v4l2-async.h:230: warning: expecting prototype for v4l2_async_notifier_add_i2c_subdev(). Prototype was for
> > > > __v4l2_async_notifier_add_i2c_subdev() instead
> > > > 
> > > > Maybe introduced by commit
> > > > 
> > > >   c1cc23625062 ("media: v4l2-async: Discourage use of v4l2_async_notifier_add_subdev")
> > > >   
> > > 
> > > Thanks for spotting this. Should be fixed by:
> > > 
> > > diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> > > index 6f22daa6f067..3785445282fc 100644
> > > --- a/include/media/v4l2-async.h
> > > +++ b/include/media/v4l2-async.h
> > > @@ -157,7 +157,7 @@ int __v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
> > >                                    struct v4l2_async_subdev *asd);
> > >  
> > >  /**
> > > - * v4l2_async_notifier_add_fwnode_subdev - Allocate and add a fwnode async
> > > + * __v4l2_async_notifier_add_fwnode_subdev - Allocate and add a fwnode async  
> > 
> > The problem with the approach is that this no longer documents the API that
> > drivers are intended to use, but the intermediate one.

Yep. the better would be to keep documenting what will be used.

> >  I guess fixing
> > this properly could require changes to kerneldoc so I have no objections to
> > the approach.

It is not a simple kernel-doc change. 

The problem is that Kernel-doc expects:


	/**
	 * foo - something
	 */
	void foo(...)

As it parses the file lines sequentially, using the parameters at
foo(...) to double-check if everything is ok.

In order for it to parse things like:

	/**
	 * foo - something
	 */

	... (some other functions in the middle)
	
	void foo(...)

Would require kernel-doc to first parse all the file, storing markups
on a separate struct, and then, on a second step, produce an output.

Even if modified to do that, there's a question if the result would
be what it is expected.

A separate thing would be to do things like:


	/**
	 * foo - something
	 */
	void __foo(...)

The problem here is that usually the arguments for __foo() are
different than the ones for foo(). See for example the macros that
have a __foo() functions with an owner argument, that are solved
on a macro called foo().

Thanks,
Mauro