Messages in this thread | | | Date | Thu, 18 Nov 2004 23:09:19 -0500 | From | Jeff Garzik <> | Subject | Re: readl/writel: swap or not to swap |
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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
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