linux-kernel - Re: [PATCH v9 0/8] pci: add pci_iomap_wc() and pci_ioremap_wc

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Date:	Tue, 21 Jul 2015 08:21:57 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	"Luis R. Rodriguez" <mcgrof@...e.com>,
	"Luis R. Rodriguez" <mcgrof@...not-panic.com>, bp@...e.de,
	arnd@...db.de, luto@...capital.net, akpm@...ux-foundation.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	tomi.valkeinen@...com, mst@...hat.com, toshi.kani@...com,
	linux-fbdev@...r.kernel.org, xen-devel@...ts.xensource.com,
	benh@...nel.crashing.org
Subject: Re: [PATCH v9 0/8] pci: add pci_iomap_wc() and pci_ioremap_wc_bar()

On Tue, Jul 21, 2015 at 10:52:52AM +0200, Ingo Molnar wrote:
> 
> * Luis R. Rodriguez <mcgrof@...e.com> wrote:
> 
> > On Wed, Jul 08, 2015 at 06:54:11PM -0700, Luis R. Rodriguez wrote:
> > > From: "Luis R. Rodriguez" <mcgrof@...e.com>
> > > 
> > > Ingo,
> > > 
> > > Boris is on vacation, he picked up these patches on his bp#tip-mm tree [0]
> > > and they have baked there for a while now. That tree receives 0-day
> > > bot testing, but other than that its not clear what other tests were
> > > run on these patches. Boris modified the commit logs a bit, and made one
> > > optimizaiton to bail early on an PCI ioremap call when it should. These
> > > patches have no modifications from what is on Boris' tree and tip-mm branch.
> > > 
> > > The 0 day build bot did find issues on Boris' tree but those are related
> > > to ioremap_uc() (already upstream) and its first use on atyfb (not
> > > upstream) -- I will be addressing a fix for that ioremap_uc() issue through
> > > another patch series prior to posting the final set for atyfb which makes
> > > use of ioremap_uc().
> > > 
> > > No issues have been found with this series. Benh did note some possible issues
> > > with expectations with what is done for write-combining for PowerPC [1] but
> > > the issue is a rather general long standing issue with semantics of ioremap --
> > > in the case for ioremap_wc() on PowerPC benh notes that writel() will never
> > > write-combine as it uses too heavy barriers. Benh notes that although
> > > writel_relaxed() today is identical to writel() this can be changed. There are
> > > other general semantics issues with ioremap() variant calls -- we seem to have
> > > all gotten together to discuss all these issues on a thread where Dan Williams
> > > is proposing to "unify ioremap prototypes and macro aliases" [1], folks
> > > intersted on these issues or semantic concerns can drop in and chime there.
> > > 
> > > Let me know if these are OK or if there are any questions.
> > > 
> > > [0] http://lkml.kernel.org/r/20150625204703.GC4898@pd.tnic
> > > [1] http://lkml.kernel.org/r/20150707095012.GQ7021@wotan.suse.de
> > 
> > Ingo,
> > 
> > Just a friendly reminder. Let me know if there are any issues or questions.
> 
> It would be nice to get an Acked-by from Bjorn for the PCI API bits.

I think the actual code of pci_ioremap_wc() and pci_ioremap_wc_bar() is
fine (although I might have named it pci_ioremap_bar_wc() for consistency).

I declined to merge or ack them myself because they're obvious extensions
of pci_ioremap() and pci_ioremap_bar(), and I would prefer that they be
exported the same way, i.e., with EXPORT_SYMBOL(), not EXPORT_SYMBOL_GPL().

I think using EXPORT_SYMBOL_GPL to express individual political aims rather
than as a hint about what might be derived work makes us look like zealots,
and that's not my style.

Bjorn
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