linux-kernel - Re: [PATCH 2/3] tty: serial: Fix build on architecture that does not have ioport

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Date:	Fri, 11 Mar 2011 15:16:18 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@...esas.com>,
	gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] tty: serial: Fix build on architecture that does not have ioport

On Friday 11 March 2011, Alan Cox wrote:
> > Some CPU's do not have ioport. Therefore, these do not have inX/outX.
> 
> The results of doing that are usually horrible and add a lot of
> configuration and ifdefs.

I guess a different implementation of this patch could convert the
driver to use ioport_map and ioread/iowrite to get rid of the
#ifdef. This might even make the driver simpler because it
does not have to special-case mmio vs. pio accesses.

Note that the 8250 driver is the basically the only driver that
uses inb/outb that can be built without setting CONFIG_ISA
or CONFIG_PCI.

> You will then get a backtrace if the methods are called rather than
> having to hack all the drivers. In addition if your platform ever has a
> PCI bridge attached to it you will now be able to replace those methods
> and provide PCI I/O space access, as you will need for many PCI devices.

That does not seem easier than writing new I/O space functions and
removing CONFIG_NO_IOPORT.

	Arnd
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