linux-kernel - Re: [PATCH] scsi: associate bio write hint with WRITE CDB

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Date:   Fri, 04 Jan 2019 01:11:49 -0500
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Randall Huang <ihhuang@...ail.org>
Cc:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        jejb@...ux.vnet.ibm.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, huangrandall@...gle.com
Subject: Re: [PATCH] scsi: associate bio write hint with WRITE CDB

Hi Randall,

> I am working on Android phone.

> The idea is to enable write hint for Turbo write UFS feature.  Turbo
> write feature in UFS 3.x is under discussion in JEDEC JC-64.  This
> patch is the under-lying framework for supporting this feature.

OK, but we can't blindly go setting GROUP NUMBER to a non-zero value.
That'll break a massive amount of devices which will fail READ/WRITE
commands with INVALID FIELD IN CDB.

So aside from requiring the device to report GROUP_SUP=1, we'll need
some sort of indication that this device supports the UFS Turbo Write
feature. If you are engaged with JEDEC on this, please tell them we'll
need a VPD page, a mode page, or something similar to use as trigger to
entertain enabling this feature.

-- 
Martin K. Petersen	Oracle Linux Engineering