[openib-general] Re: librdmacm/ucma

[Michael S. Tsirkin]

Quoting r. Sean Hefty <sean.hefty at intel.com>:
> Subject: RE: librdmacm/ucma
> 
> >- dependency on libsysfs
> >  I propose we don't get into this again. I know we have it in ibverbs
> >  but let's avoid for new code.
> >
> >- negative error codes
> >  I think this is kernel practice, in userspace we
> >  either set errno and return -1, or simply return
> >  positive error code: otherwise utilities like strerror
> >  do not work
> 
> We can convert all negative error codes to positive.

That's OK.

> >- abi versioning
> >  The RDMA_USER_CM_MAX_ABI_VERSION idea is broken - it makes it so that you are
> >  required to upgrade userspace to run on older kernels.
> >  Bailing out in userspace if the kernel is too new is not good - please
> >  remove this test.
> 
> There is both a minor and major number.  A given library should support anything
> between its known versions.  Can you be more specific about the problem?

The library now has
min = 1 max = 2
this means that any ABI update in kernel will break userspace.

People expect to be able to update kernel and keep old userspace.

-- 
MST