Re: [PATCH] RM9000 serial driver

From: Thomas Koeller <thomas.koeller@baslerweb.com>
To: "Russell King" <rmk@arm.linux.org.uk>
Cc: "Sergei Shtylyov" <sshtylyov@ru.mvista.com>,
	"Yoichi Yuasa" <yoichi_yuasa@tripeaks.co.jp>,
	linux-serial@vger.kernel.org, ralf@linux-mips.org,
	linux-mips@linux-mips.org,
	"Thomas Köller" <thomas@koeller.dyndns.org>
Subject: Re: [PATCH] RM9000 serial driver
Date: Wed, 30 Aug 2006 23:28:47 +0200	[thread overview]
Message-ID: <200608302328.47944.thomas.koeller@baslerweb.com> (raw)
In-Reply-To: <20060830121216.GA25699@flint.arm.linux.org.uk>

On Wednesday 30 August 2006 14:12, Russell King wrote:

> iotype is all about the access method used to access the registers of
> the device, be it by byte or word, and it also takes account of any
> variance in the addressing of the registers.
>
> It does not refer to features or bugs in any particular implementation.

That's what I assumed, too - it seemed obvious. And it seemed equally
obvious that it is the port type that encodes the the implementation's
peculiarities. Among these are the register offset mapping requirements,
so I assumed these should depend on the port type as well.

Now Sergei strongly insist that it's the iotype that should be checked
whenever to get to the hardware type. I still do not quite understand how
that is supposed to work. If I have a PCI device, for example, then the
iotype will always be either UPIO_MEM or UPIO_PORT, so how could I learn
something about the hardware implementation by looking at these values?
Or is the assumption that devices on a standard bus will always be of
a standard type?

Thomas

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