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Message-Id: <20090526.022508.238274281.davem@davemloft.net>
Date: Tue, 26 May 2009 02:25:08 -0700 (PDT)
From: David Miller <davem@...emloft.net>
To: arnd@...db.de
Cc: linuxppc-dev@...abs.org, wg@...ndegger.com,
devicetree-discuss@...abs.org, netdev@...r.kernel.org
Subject: Re: [net-next-2.6 PATCH v2] can: SJA1000: generic OF platform bus
driver
From: Arnd Bergmann <arnd@...db.de>
Date: Tue, 26 May 2009 10:10:30 +0100
> On Monday 25 May 2009, Wolfgang Grandegger wrote:
>> > Right, that makes sense. However, most drivers use the field to store the
>> > physical address, not the iomap token. Maybe there should be a new field
>> > in struct sja1000_priv for the virtual address, but that would be a change
>> > to the base driver, not just to the OF portion.
>>
>> Is that common practice? If yes, I will add a member to store the
>> virtual address to struct sja1000_priv.
>
> I grepped through the network driver for usage of ->base_addr, and
> it's somewhat inconsistent. The majority of the users use it for
> a physical address, but there are also a few that use it for the
> __iomem token.
>
> Casts between unsigned long and qualified (__iomem, __user, const, ...)
> pointers do not cause a warning, but can easily lead to bugs when
> another user casts to an unqualified pointer.
It's such a baroque thing, there is no reason to set it at all if you
ask me. It's only use is to allow ISA and similar primitive bus
devices to have their I/O ports changed via ifconfig.
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