[openib-general] Re: common userspace support

[Michael S. Tsirkin]

Quoting r. Sean Hefty <mshefty at ichips.intel.com>:
> Subject: common userspace support
> 
> I'm implementing the userspace CMA and noticed that there are a couple of areas 
> where userspace support overlaps.
> 
> For example, both the CMA and IB CM need to copy path records between userspace 
> and the kernel.  They also copy QP attributes, which would also be needed by 
> verbs at some point to support query QP.  In these cases, the data structures 
> passed between userspace and the kernel are the same, as is the code to copy them.
> 
> Does anyone have a preference for how to deal with this issue on both the kernel 
> and userspace sides?
> 
> My thinking is that for the kernel, the kernel structures would be defined in a 
> common header, with functions exported to copy to/from them.  This results in 
> additional dependencies between modules.  (E.g. rdma_ucm would require ib_uverbs 
> and ib_usa modules.  ib_user_verbs.h would define the QP attribute structure and 
> uverbs_?.c would export copy routines.)
> 
> For userspace, we can do something similar, which would build dependencies 
> between the different libraries.
> 
> - Sean


Common header files/structures might make some sense, but what would
the routines do, besides copy to/from user?
Could you give an example?

-- 
MST