Re: [RFC PATCH 2/5] scsi: ufs: Add UFS-feature layer

[Bart Van Assche <bvanassche@acm.org>]

On 2020-06-11 19:27, Daejun Park wrote:
>>> @@ -2525,6 +2525,8 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
>>>  
>>>    ufshcd_comp_scsi_upiu(hba, lrbp);
>>>  
>>> +  ufsf_ops_prep_fn(hba, lrbp);
>>> +
>>>    err = ufshcd_map_sg(hba, lrbp);
>>>    if (err) {
>>>      lrbp->cmd = NULL;
> 
>> What happens if a SCSI command is retried and hence ufsf_ops_prep_fn()
>> is called multiple times for the same SCSI command?
>
> Developers of UFS features should implement it so that prep_fn does not have
> any problems even if it processes the same SCSI command multiple times.
> In HPB feature, prep_fn modifies only upiu  structure. So it is ok to call
> it multiple times because the upiu is rebuilt from ufshcd_comp_scsi_upiu().

Please make sure that this expectation is documented somewhere.

Thanks,

Bart.