linux-kernel - Re: [RFC v1 01/16] lib: devres: don't enclose pcim_*() functions in CONFIG_HAS

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Message-ID: <20121211173450.GW14363@n2100.arm.linux.org.uk>
Date:	Tue, 11 Dec 2012 17:34:50 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>,
	Yehuda Yitschak <yehuday@...vell.com>,
	Maen Suleiman <maen@...vell.com>,
	Jason Cooper <jason@...edaemon.net>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	linux-kernel@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Eran Ben-Avi <benavi@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Lior Amsalem <alior@...vell.com>,
	Shadi Ammouri <shadi@...vell.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [RFC v1 01/16] lib: devres: don't enclose pcim_*() functions
	in CONFIG_HAS_IOPORT

On Tue, Dec 11, 2012 at 05:16:10PM +0000, Alan Cox wrote:
> > Correct.  If HAS_IOPORT is not selected then we are potentially missing
> > the dependent functions (because the platform has no IOPORT support) _or_
> > it does have ISA/PCI IO spaces _but_ they're not mappable via the
> > ioport_map() mechanism due to some non-linearity involved in the
> > translation.
> > 
> > To make that second point clear, that's platforms where:
> > 
> > 	ioport_map(addr + 4) != ioport_map(addr) + 4.
> 
> For inb/inw and friends this shouldn't matter.

Exactly, and you wouldn't be using inb/inw with ioport_map().

The problem comes when you end up trying to deal with stuff which
uses ioread{8,16} on ioport_map() cookies where it's assumed that
adding N to the cookie is the same as adding N to the port address.

Thankfully those platforms aren't going to be a part of the single
zImage project...
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