struct rdma_conn_param uses u8 for responder_resources, initiator_depth and private_data_len

struct rdma_conn_param uses u8 for responder_resources, initiator_depth and private_data_len

[Stefan Metzmacher]

Hi,

this mail is triggered by the discussion in this thread on
linux-cifs:
https://lore.kernel.org/linux-cifs/f551bf7f-697a-4298-a62c-74da18992204@samba.org/T/#t

In include/rdma/rdma_cm.h we have this:

struct rdma_conn_param {
         const void *private_data;
         u8 private_data_len;
         u8 responder_resources;
         u8 initiator_depth;
         u8 flow_control;
         u8 retry_count;         /* ignored when accepting */
         u8 rnr_retry_count;
         /* Fields below ignored if a QP is created on the rdma_cm_id. */
         u8 srq;
         u32 qp_num;
         u32 qkey;
};

The iwarp MPA v2 negotiation can handle values up to
0x3fff for responder_resources and initiator_depth.
And private_data_len can be 0xffff for MPA v1 and
0xffff - 4 for MPA v2.

I just found that ROCE only supports u8 in the CM ConnectRequest
(and I guess it's ROCE v1 and v2 as well as Infiniband,
but I've only every seen ROCE v2 captures).

BTW: does ROCE also support private data and if how much?

So is it desired to limit iwarp to u8 values too?

Thanks!
metze

Re: struct rdma_conn_param uses u8 for responder_resources, initiator_depth and private_data_len

[Stefan Metzmacher]

Am 21.08.25 um 23:04 schrieb Stefan Metzmacher via samba-technical:
> Hi,
> 
> this mail is triggered by the discussion in this thread on
> linux-cifs:
> https://lore.kernel.org/linux-cifs/f551bf7f-697a-4298-a62c-74da18992204@samba.org/T/#t
> 
> In include/rdma/rdma_cm.h we have this:
> 
> struct rdma_conn_param {
>          const void *private_data;
>          u8 private_data_len;
>          u8 responder_resources;
>          u8 initiator_depth;
>          u8 flow_control;
>          u8 retry_count;         /* ignored when accepting */
>          u8 rnr_retry_count;
>          /* Fields below ignored if a QP is created on the rdma_cm_id. */
>          u8 srq;
>          u32 qp_num;
>          u32 qkey;
> };

struct iw_cm_event {
         enum iw_cm_event_type event;
         int                      status;
         struct sockaddr_storage local_addr;
         struct sockaddr_storage remote_addr;
         void *private_data;
         void *provider_data;
         u8 private_data_len;
         u8 ord;
         u8 ird;
};

Also has them as u8...

> The iwarp MPA v2 negotiation can handle values up to
> 0x3fff for responder_resources and initiator_depth.
> And private_data_len can be 0xffff for MPA v1 and
> 0xffff - 4 for MPA v2.
> 
> I just found that ROCE only supports u8 in the CM ConnectRequest
> (and I guess it's ROCE v1 and v2 as well as Infiniband,
> but I've only every seen ROCE v2 captures).
> 
> BTW: does ROCE also support private data and if how much?
> 
> So is it desired to limit iwarp to u8 values too?
> 
> Thanks!
> metze
> 

Re: struct rdma_conn_param uses u8 for responder_resources, initiator_depth and private_data_len

[Namjae Jeon]

On Fri, Aug 22, 2025 at 6:04 AM Stefan Metzmacher <metze@samba.org> wrote:
>
> Hi,
CC: Jason and Leon.
>
> this mail is triggered by the discussion in this thread on
> linux-cifs:
> https://lore.kernel.org/linux-cifs/f551bf7f-697a-4298-a62c-74da18992204@samba.org/T/#t
>
> In include/rdma/rdma_cm.h we have this:
>
> struct rdma_conn_param {
>          const void *private_data;
>          u8 private_data_len;
>          u8 responder_resources;
>          u8 initiator_depth;
>          u8 flow_control;
>          u8 retry_count;         /* ignored when accepting */
>          u8 rnr_retry_count;
>          /* Fields below ignored if a QP is created on the rdma_cm_id. */
>          u8 srq;
>          u32 qp_num;
>          u32 qkey;
> };
>
> The iwarp MPA v2 negotiation can handle values up to
> 0x3fff for responder_resources and initiator_depth.
> And private_data_len can be 0xffff for MPA v1 and
> 0xffff - 4 for MPA v2.
>
> I just found that ROCE only supports u8 in the CM ConnectRequest
> (and I guess it's ROCE v1 and v2 as well as Infiniband,
> but I've only every seen ROCE v2 captures).
>
> BTW: does ROCE also support private data and if how much?
>
> So is it desired to limit iwarp to u8 values too?
>
> Thanks!
> metze