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Subject: Re: [RFC PATCH 2/5] scsi: ufs: Add UFS-feature layer
To:     daejun7.park@samsung.com, ALIM AKHTAR <alim.akhtar@samsung.com>,
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Cc:     "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sang-yoon Oh <sangyoon.oh@samsung.com>,
        Sung-Jun Park <sungjun07.park@samsung.com>,
        yongmyung lee <ymhungry.lee@samsung.com>,
        Jinyoung CHOI <j-young.choi@samsung.com>,
        Adel Choi <adel.choi@samsung.com>,
        BoRam Shin <boram.shin@samsung.com>
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From:   Bart Van Assche <bvanassche@acm.org>
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Date:   Thu, 11 Jun 2020 21:28:34 -0700
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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.