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Date: Wed, 1 Jul 2015 08:59:48 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 2/6] arch: unify ioremap prototypes and macro aliases
Message-ID: <20150701065948.GA4355@lst.de>
References: <20150622081028.35954.89885.stgit@dwillia2-desk3.jf.intel.com> <20150622082427.35954.73529.stgit@dwillia2-desk3.jf.intel.com> <20150622161002.GB8240@lst.de> <CAPcyv4h5OXyRvZvLGD5ZknO-YUPn675YGv0XdtW1QOO9qmZsug@mail.gmail.com> <20150701062352.GA3739@lst.de> <CAMuHMdUO4uSWH1Qc0SfDTLuXbiG2N9fq8Tf6j+3RoqVKdPugbA@mail.gmail.com>
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To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Christoph Hellwig <hch@lst.de>, Dan Williams <dan.j.williams@intel.com>, Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Ross Zwisler <ross.zwisler@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Juergen Gross <jgross@suse.com>, X86 ML <x86@kernel.org>, "Kani, Toshimitsu" <toshi.kani@hp.com>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Luis Rodriguez <mcgrof@suse.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Stefan Bader <stefan.bader@canonical.com>, Andy Lutomirski <luto@amacapital.net>, Linux MM <linux-mm@kvack.org>, Ralf Baechle <ralf@linux-mips.org>, Henrique de Moraes Holschuh <hmh@hmh.eng.br>, Michael Ellerman <mpe@ellerman.id.au>, Tejun Heo <tj@kernel.org>, Paul Mackerras <paulus@samba.org>, Russell King - ARM Linux <linux@arm.linux.org.uk>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>

On Wed, Jul 01, 2015 at 08:55:57AM +0200, Geert Uytterhoeven wrote:
> >
> > I think doing this at runtime might be a better idea.  E.g. a
> > ioremap_flags with the CACHED argument will return -EOPNOTSUP unless
> > actually implemented.  On various architectures different CPUs or
> > boards will have different capabilities in this area.
> 
> So it would be the responsibility of the caller to fall back from
> ioremap(..., CACHED) to ioremap(..., UNCACHED)?
> I.e. all drivers using it should be changed...

All of the zero users we currently have will need to be changed, yes.

Note that I propose to leave ioremap(), aka ioremap_flags(..., 0) as
a default that always has to work, -EOPNOTSUP is only a valid return
value for non-default flaga.

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