Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH 09/11] swiotlb-xen: simplify cache maintainance | From | Andrew Cooper <> | Date | Fri, 6 Sep 2019 15:07:42 +0100 |
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On 06/09/2019 15:01, Christoph Hellwig wrote: > On Fri, Sep 06, 2019 at 09:52:12AM -0400, Boris Ostrovsky wrote: >> We need nop definitions of these two for x86. >> >> Everything builds now but that's probably because the calls are under >> 'if (!dev_is_dma_coherent(dev))' which is always false so compiler >> optimized is out. I don't think we should rely on that. > That is how a lot of the kernel works. Provide protypes only for code > that is semantically compiled, but can't ever be called due to > IS_ENABLED() checks. It took me a while to get used to it, but it > actually is pretty nice as the linker does the work for you to check > that it really is never called. Much better than say a BUILD_BUG_ON().
Yeah - its a weird concept to get used to, but it results in much clearer code.
~Andrew
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