Re: readl/writel: swap or not to swap

[Jeff Garzik <jgarzik@pobox.com>]

Yasushi SHOJI wrote:
> At Sat, 13 Nov 2004 21:20:03 +0900,
> yashi wrote:
> [...]
> 
>>>Why not just use __raw_readl/__raw_writel?
>>>
>>>That's what they exist for, and they still do any IO accesses correctly, 
>>>which a direct store does not do (it would seriously break on older 
>>>alphas, for example).
>>
>>sorry for a dumb question but should readl/writel on big endian system
>>swap like ppc does?
> 
> 
> I guess everyone is busy hacking.  but can at least someone give me a
> hit?
> 
> I'm worring about this issue because I'm about to use two deferent
> linux arch on same board.  it's based on reconfigurable device so I
> can configure to have deferent cpu on it.
> 
> if you are using two deferent arch of linux, it's natual to think you
> want to share all device drivers.  but if one arch swap with readl and
> the other doesn't, I have to abstruct these low level access
> methods. (given that those to arch are same endian and connected with
> same bus and to the same devices)
> 
> is there any rule we should follow?  Is the ppc way the right
> direction to follow? I can ifdef anytime for my own use but I just
> want to know what _should_ be done.


readl()/writel() are defined as being for the PCI bus (little endian). 
As such, they should swap on big endian platforms.

	Jeff