Messages in this thread | | | Date | Fri, 7 Feb 2020 09:47:32 +0100 | From | Jean-Philippe Brucker <> | Subject | Re: [PATCH 3/3] iommu/uapi: Add helper function for size lookup |
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On Mon, Feb 03, 2020 at 02:41:02PM -0800, Jacob Pan wrote: > Yeah, that would work as well. I just feel IOMMU UAPI is unlikely to get > updated frequently, should be much less than adding new capabilities. > I think argsz could be viewed as the version field set by the > user, minsz is what kernel current code supports. > > So let me summarize the options we have > 1. Disallow adding new members to each structure other than reuse > padding bits or adding union members at the end. > 2. Allow extension of the structures beyond union, but union size has > to be fixed with reserved spaces > 3. Adopt VFIO argsz scheme, I don't think we need version for each > struct anymore. argsz implies the version that user is using assuming > UAPI data is extension only. > > Jean, Eric, any comments? My preference is #1. In the apocalyptic event > when we run out of padding, perhaps we can introduce a new API_v2 :)
I agree, new extensions will most likely want to extend the vendor specific structures at the end rather than introduce new common fields, so I prefer #1 which avoids fixing the union size.
Thanks, Jean
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