linux-kernel - Re: [PATCH v2 1/2] scsi: ufs: core: Remove unnecessary if statement

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Date:   Tue, 11 Oct 2022 11:39:27 +0200
From:   Bean Huo <beanhuo@...pp.de>
To:     daejun7.park@...sung.com, ALIM AKHTAR <alim.akhtar@...sung.com>,
        "avri.altman@....com" <avri.altman@....com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>
Cc:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] scsi: ufs: core: Remove unnecessary if statement

On Tue, 2022-10-11 at 11:21 +0900, Daejun Park wrote:
> Hi Bean Huo,
> 
> I think ufs_is_valid_unit_desc_lun() is also used for
> wb_buf_alloc_units_show() in ufs-sysfs.c.
> So just removing this if-checkup will make different result when
> check lun value.
> 

Hi Daejun,

Thanks for your review on the patch. Yes, I understood what you mean.
But I don't think that's the problem. Without this patch, access on
sysfs node "wb_shared_alloc_units" would get "invalid argument", while
with this patch sysfs would return 00. According to the UFS
specification:

"If this value is ‘0’, then the WriteBooster is not supported for this
LU. The Logical unit among LU0 ~ LU7 can be configured for WriteBooster
Buffer. Otherwise, whole WriteBooster Buffer configuration in this
device is invalid."

Per my understanding,  with this patch,  there is still no miss-
explanation of this sysfs node. The key purpose of this patch is to
remove any nonsense logical during the booting stage.

please have a think my comments. thanks.

Kind regards,
Bean

> Thanks,
> Daejun
> 
> > From: Bean Huo <beanhuo@...ron.com>
> > 
> > LUs with WB potential support are properly checked in ufshcd_wb_pro
> > be()
> > before calling ufshcd_read_unit_desc_param(), so remove this unnece
> > ssary
> > if-
> > checkup in ufs_is_valid_unit_desc_lun() to match its function defin
> > ition.