Re: [PATCH RFC v2 02/10] IB/core: Introduce Signature Verbs API

[Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 11/3/2013 4:41 PM, Bart Van Assche wrote:
> On 3/11/2013 4:15, Sagi Grimberg wrote:
>> On 11/1/2013 8:46 PM, Bart Van Assche wrote:
>>> On 31/10/2013 5:24, Sagi Grimberg wrote:
>>>> +/**
>>>> + * Signature T10-DIF block-guard types
>>>> + */
>>>> +enum ib_t10_dif_bg_type {
>>>> +    IB_T10DIF_CRC,
>>>> +    IB_T10DIF_CSUM
>>>> +};
>>>
>>> In SPC-4 paragraph 4.22.4 I found that the T10-PI guard is the CRC
>>> computed from the generator polynomial x^16 + x^15 + x^11 + x^9 + x^8
>>> + x^7 + x^5 + x^4 + x^2 + x + 1. Could you tell me where I can find
>>> which guard computation method IB_T10DIF_CSUM corresponds to ?
>>>
>>> Bart.
>>
>> The IB_T10DIF_CSUM  computation method corresponds to IP checksum rules.
>> this is aligned with SHOST_DIX_GUARD_IP guard type.
>
> Since the declarations added in <rdma/ib_verbs.h> constitute an 
> interface definition I think it would help if it would be made more 
> clear what these two symbols stand for. How about mentioning the names 
> of the standards these two guard computation methods come from ? An 
> alternative is to add a comment like the one above 
> scsi_host_guard_type in <scsi/scsi_host.h> which explains the two 
> guard computation methods well:
>
> /*
>  * All DIX-capable initiators must support the T10-mandated CRC
>  * checksum.  Controllers can optionally implement the IP checksum
>  * scheme which has much lower impact on system performance.  Note
>  * that the main rationale for the checksum is to match integrity
>  * metadata with data.  Detecting bit errors are a job for ECC memory
>  * and buses.
>  */
>
> Bart.
>

Agreed,

I'll comment on each type correspondence (T10-DIF CRC checksum and IP 
checksum).

Sagi.
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html