Re: [PATCH v20 05/20] nvme-tcp: Add DDP offload control path

[Aurelien Aptel <aaptel@nvidia.com>]

Hi Sagi,

Sagi Grimberg <sagi@grimberg.me> writes:
>> +     ok = ulp_ddp_query_limits(netdev, &ctrl->ddp_limits,
>> +                               ULP_DDP_NVME, ULP_DDP_CAP_NVME_TCP,
>> +                               ctrl->ctrl.opts->tls);
>> +     if (!ok) {
>
> please use a normal name (ret).

Ok, we will rename to ret and make ulp_ddp_query_limits() return int 0
on success to be consistent with the name.

> Plus, its strange that a query function receives a feature and returns
> true/false based on this. The query should return the limits, and the
> caller should look at the limits and see if it is appropriately
> supported.

We are not sure how to proceed as this seems to conflict with what you
suggested in v12 [1] about hiding the details of checking supports in
the API. Limits just dictate some constants the nvme-layer should use
once we know it is supported.

We can rename ulp_ddp_query_limits() to ulp_ddp_check_support(). This
function checks the support of the specified offload capability and also
returns the limitations of it.

Alternatively, we can split it in 2 API functions (check_support
and query_limits).

Let us know what you prefer.

Thanks

1: https://lkml.kernel.org/netdev/bc5cd2a7-efc4-e4df-cae5-5c527dd704a6@grimberg.me/