Hi Konrad, On Wednesday 20 August 2014 09:02:50 Konrad Rzeszutek Wilk wrote: > On Tue, Aug 19, 2014 at 10:52:46PM +0200, Laurent Pinchart wrote: > > On Tuesday 19 August 2014 11:40:24 Olav Haugan wrote: > > > On 8/19/2014 9:11 AM, Laurent Pinchart wrote: > > > > On Tuesday 19 August 2014 13:59:54 Joerg Roedel wrote:
[snip] > > > >> Okay, since you add these call-backs to all drivers I think I can > > > >> live with not doing a pointer check here. > > > > > > > > I suggested doing a > > > > > > > > if (ops is not NULL) > > > > return ops(); > > > > else > > > > return default_ops(); > > > > > > > > to avoid modifying all drivers. I'm not sure why that wasn't received > > > > with much enthusiasm. > > > > > > Both Thierry R. and Konrad W. argued for modifying the drivers instead > > > so I implemented what the majority wanted. :-) > > > > I'm not blaming you :-) I was just wondering what their rationale was. > > a). To be inline with the usage of this API. > > For this particular case the other functions (but maybe I missed some) > follow the idea that they implement the ops->func for every operation > and they don't have an fallback. That's because the other functions are mandatory, while this particular one is just an optimization and can be implemented generically. > b) Follow what x86 maintainers prefer (based on other API calls, > such as x86_init or any other platform overrides). > > c). When there are new IOMMUs it has to take in-to account all of the > function ops. If they fail to implement all of them the kernel > crashes instead of working (but maybe working incorrectly). I don't think that applies in this case, the generic implementation should work in all cases. > d). Lastly, we also want the bloat of kernel. If the compiler decides > to roll in the fallback implementation for 'iommu_map_sg' in - it will > needlessly expand the kernel wherever we use 'iommu_map_sg' call with > a fallback implementation (which might not be called 99% of time). > > Having the little inline static just do 'func_ops->func' will > stop the compiler from optimizing too much and convert this just > to a simple function. That's an argument I can buy. -- Regards, Laurent Pinchart _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
