Re: [PATCH V1 for-next 1/2] IB/core: Report LSO capabilities when querying device

[Matan Barak <matanb-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 28/04/2016 00:54, Hefty, Sean wrote:
>>> +struct ib_lso_caps {
>>> +	u32 max_lso;
>>> +	u32 supported_qpts; /* Use enum ib_qp_type */
>>
>> So this is a bitmap of the qps supported? And thus we have a limit now of
>> 32 QP types. That needs to be documented and  you need a BUILD_BUG_ON
>> somewhere in case IB_QPT_MAX becomes larger than 32. Also needs to be
>> better commented so we know this is a bitmap.
>
> I think it would make more sense to indicate what protocol, or specific aspect of a protocol, are being offloaded.  Some qp types support LSO as a matter of practice.
>

For a lot of applications, we want to hide the lower level protocol. For 
example, we try hard to hide whether IB/RoCE is used by an application. 
Thus, is it wise to expose this thing in API?
A user creates a UD QP, he doesn't know or care whether the lower layer 
is Ethernet (RoCE v1/V2) or IB.

I agree that the max_lso could be different for various QP types and 
maybe probing a QP type would be favorable that getting this information 
in a generic query_device.
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