Re: [PATCH V2] libibverbs: Allow arbitrary int values for MTU

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 7/17/2013 4:41 PM, Hefty, Sean wrote:
>> I hadn't looked at the kernel side yet; I was waiting for the userspace side to
>> sort itself out first.
> I think it makes sense to start with how user space can get the data.  Without eating up reserved fields, we're starting with 8 bit values.
>
>> Hmm.  16 bits is probably enough for the MTU values, but still, changing kern-
>> abi.h will be problematic from an ABI perspective.  Do people care about the
>> kernel ABI, or is that mainly a userspace issue?
> Well, we definitely care about the kernel to user ABI.
>
> I can't imagine that we're dealing with more than a handful of actual MTU values.  Maybe the simplest thing is to extend the mtu enum to include what new values are needed, plus add a function to convert it.  (Can we call mulligan?)
>
> I don't know how iwarp handles this.  Does it just report the wrong mtu, since it doesn't necessarily matter?  Steve - any idea here?

The iwarp drivers just report the nearest mtu enum.  Apps don't need it 
for iwarp like they do for ib.


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