linux-kernel - Re: [PATCH v4 2/5] lib: devres: add pcim_iomap

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Date:	Fri, 1 May 2015 02:20:04 +0200
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>, mst@...hat.com,
	plagnioj@...osoft.com, tomi.valkeinen@...com, airlied@...ux.ie,
	daniel.vetter@...el.com, linux-fbdev@...r.kernel.org,
	luto@...capital.net, cocci@...teme.lip6.fr,
	linux-kernel@...r.kernel.org, Toshi Kani <toshi.kani@...com>,
	Suresh Siddha <sbsiddha@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Juergen Gross <jgross@...e.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Dave Airlie <airlied@...hat.com>,
	Antonino Daplas <adaplas@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>, venkatesh.pallipadi@...el.com,
	Stefan Bader <stefan.bader@...onical.com>,
	Ville Syrjälä <syrjala@....fi>,
	Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
	Borislav Petkov <bp@...e.de>, Davidlohr Bueso <dbueso@...e.de>,
	konrad.wilk@...cle.com, ville.syrjala@...ux.intel.com,
	david.vrabel@...rix.com, jbeulich@...e.com,
	Roger Pau Monné <roger.pau@...rix.com>,
	xen-devel@...ts.xensource.com, linux-pci@...r.kernel.org
Subject: Re: [PATCH v4 2/5] lib: devres: add pcim_iomap_wc() variants

On Thu, Apr 30, 2015 at 04:46:38PM -0500, Bjorn Helgaas wrote:
> On Thu, Apr 30, 2015 at 07:27:23PM +0200, Luis R. Rodriguez wrote:
> > On Thu, Apr 30, 2015 at 11:26:47AM -0500, Bjorn Helgaas wrote:
> 
> > > I don't see users of either pcim_iomap_wc() or pcim_iomap_wc_regions() so
> > > far.  Did I miss them, or do you just expect them in the near future?
> > 
> > The later, and also I hate seeing folks later add code under EXPORT_SYMBOL()
> > rather than EXPORT_SYMBOL_GPL() so I figure I'd rather do it first. It happened
> > recently in my v1 series, someone beat me to a write-combining export symbol
> > and changed it to EXPORT_SYMBOL(). Feel free to drop this though but I hope
> > no one out there then tries to just add an EXPORT_SYMBOL() later for this...
> 
> Why do you want them to be EXPORT_SYMBOL_GPL?  I would expect them to be
> exported the same way pcim_iomap(), pcim_iomap_regions(), and ioremap_wc()
> are exported, i.e., with EXPORT_SYMBOL.
>> 
> Per Documentation/DocBook/kernel-hacking.tmpl, EXPORT_SYMBOL_GPL "implies
> that the function is considered an internal implementation issue, and not
> really an interface."  I don't think these are internal implementation
> issues.

What Documentation/DocBook/kernel-hacking.tmpl states over EXPORT_SYMBOL_GPL()
is old and in no way reflects current trends and reality. For instance, some
folks believe that if some code has EXPORT_SYMBOL() declared that they can use
it on proprietary modules. This is terribly incorrect, quite a few developers
do not in any way stand by this as a "needed" clarification on their code [0].
I'm one of them, but to be even more clear on this I simply *always* use
EXPORT_SYMBOL_GPL() to remove any possible doubt over this on any symbols
that I export. Heck, even tons of driver library code uses EXPORT_SYMBOL_GPL().

[0] https://lkml.org/lkml/2012/4/20/402

  Luis
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