On Fri, Dec 5, 2014 at 12:35 PM, Robin Murphy <robin.mur...@arm.com> wrote: > Hi Will, > > On 05/12/14 12:10, Will Deacon wrote: > [...] >>>> >>>> Do you expect drivers to modify that *priv pointer after the ops >>>> structure is registered? I'd be very surprised if that was the use >>>> case. It's fine for the driver to register a non-const version, but >>>> once it is registered, the infrastructure can treat it as const from >>>> then on. >>> >>> >>> Possibly not - certainly my current port of the ARM SMMU which makes use >>> of *priv is only ever reading it - although we did also wave around >>> reasons for mutable ops like dynamically changing the pgsize_bitmap and >>> possibly even swizzling individual ops for runtime reconfiguration. On >>> consideration though, I'd agree that things like that are mad enough to >>> stay well within individual drivers if they did ever happen, and >>> certainly shouldn't apply to this bit of the infrastructure at any rate. >> >> >> I certainly need to update the pgsize_bitmap at runtime because I don't >> know the supported page sizes until I've both (a) probed the hardware >> and (b) allocated page tables for a domain. We've already discussed >> moving the pgsize_bitmap out of the ops, but moving it somewhere where >> it remains const doesn't really help. > > > We can safely cast the call to get_ops in the SMMU driver though, since > we'll know that we put a mutable per-instance ops in there in the first > place. At least that way drivers that aren't taking advantage and just pass > their static const ops around shouldn't provoke warnings. I deliberately > didn't touch anything beyond get_ops as that would be too disruptive. > >> Can I just take the patch that Grant acked, in the interest of getting >> something merged? As you say, there's plenty of planned changes in this >> area anyway. I plan to send Olof a pull request this afternoon. > > > Grant, Thierry? Personally I'm not fussed either way - the sooner something > goes in, the sooner I can carry on working at replacing it :D
I've already acked it. Why are we still talking about it? :-D g. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
