linux-kernel - Re: [PATCH v1 1/5] scsi: Adjust DBD setting in mode sense for caching mode page per LLD

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Date:   Mon, 28 Oct 2019 07:58:39 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.org>, asutoshd@...eaurora.org,
        nguyenb@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com
Cc:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/5] scsi: Adjust DBD setting in mode sense for caching
 mode page per LLD

On 10/27/19 8:50 PM, Can Guo wrote:
> Host sends MODE_SENSE_10 with caching mode page, to check if the device
> supports the cache feature.
> Some LLD standards requires DBD field to be set to 1.

Which LLD standard are you referring to? Please mention at least one 
name of such a standard in the patch description.

> Change-Id: I0c8752c1888654942d6d7e6e0f6dc197033ac326

Change-IDs should be left out from upstream patches. Does the presence 
of this ID mean that this patch has not been verified with checkpatch? 
 From the checkpatch source code:

# Check for unwanted Gerrit info
if ($in_commit_log && $line =~ /^\s*change-id:/i) {
	ERROR("GERRIT_CHANGE_ID",
	      "Remove Gerrit Change-Id's before submitting upstream.\n"\
		 . $herecurr);
}

> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index aab4ed8..6d8194f 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2629,6 +2629,7 @@ static int sd_try_rc16_first(struct scsi_device *sdp)
>   {
>   	int len = 0, res;
>   	struct scsi_device *sdp = sdkp->device;
> +	struct Scsi_Host *host = sdp->host;
>   
>   	int dbd;
>   	int modepage;
> @@ -2660,7 +2661,10 @@ static int sd_try_rc16_first(struct scsi_device *sdp)
>   		dbd = 8;
>   	} else {
>   		modepage = 8;
> -		dbd = 0;
> +		if (host->set_dbd_for_caching)
> +			dbd = 8;
> +		else
> +			dbd = 0;
>   	}
>   
>   	/* cautiously ask */
> diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
> index 2c3f0c5..3900987 100644
> --- a/include/scsi/scsi_host.h
> +++ b/include/scsi/scsi_host.h
> @@ -650,6 +650,12 @@ struct Scsi_Host {
>   	unsigned no_scsi2_lun_in_cdb:1;
>   
>   	/*
> +	 * Set "DBD" field in mode_sense caching mode page in case it is
> +	 * mandatory by LLD standard.
> +	 */
> +	unsigned set_dbd_for_caching:1;
> +
> +	/*
>   	 * Optional work queue to be utilized by the transport
>   	 */
>   	char work_q_name[20];

Since this patch by itself has no effect, please resubmit this patch 
together with the LLD patch that sets set_dbd_for_caching.

Thanks,

Bart.