linux-kernel - RE: [PATCH 3/3] scsi: ufs-sysfs: Add sysfs entries for temperature notification

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Message-ID: <DM6PR04MB6575999F5D92901B5D2791EFFCCE9@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Thu, 2 Sep 2021 06:52:10 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Bart Van Assche <bvanassche@....org>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bean Huo <beanhuo@...ron.com>
Subject: RE: [PATCH 3/3] scsi: ufs-sysfs: Add sysfs entries for temperature
 notification

> 
> On 9/1/21 5:37 AM, Avri Altman wrote:
> > +What:
> /sys/bus/platform/drivers/ufshcd/*/attributes/case_rough_temp
> > +Date:                September 2021
> > +Contact:     Avri Altman <avri.altman@....com>
> > +Description: The device case rough temperature
> (bDeviceCaseRoughTemperature
> > +             attribute). It is termed "rough" due to the inherent inaccuracy
> > +             of the temperature sensor inside a semiconductor device,
> > +             e.g. +- 10 degrees centigrade error range.
> 
> My understanding is that the word Celsius is more common than centigrade
> so please use Celsius instead of centigrade. See also
> https://www.brannan.co.uk/celsius-centigrade-and-fahrenheit/
Done.

> 
> > +             allowable range is [-79..170].
> > +             The temperature readings are in decimal degrees Celsius.
> > +
> > +             Please note that the Tcase validity depends on the state of the
> > +             wExceptionEventControl attribute: it is up to the user to
> > +             verify that the applicable mask (TOO_HIGH_TEMP_EN, and / or
> > +             TOO_LOW_TEMP_EN) is set for the exception handling control.
> > +             This can be either done by ufs-bsg or ufs-debugfs.
> 
> Instead of making the user verify whether case_rough_temp is valid,
> please modify the kernel code such that case_rough_temp only reports a
> value if that value is valid. One possible approach is to make the show
> method return an error code if case_rough_temp is not valid.
But it does.
Just wanted to document that exception control is controlled from user space,
And avoid the eyebrow raises when getting invalid temperature reading.

>Another and
> probably better approach is to define a sysfs attribute group and to
> make case_rough_temp visible only if it is valid.
> 
> > diff --git a/drivers/scsi/ufs/ufs-sysfs.c b/drivers/scsi/ufs/ufs-sysfs.c
> > index 5c405ff7b6ea..a9abe33c40e4 100644
> > --- a/drivers/scsi/ufs/ufs-sysfs.c
> > +++ b/drivers/scsi/ufs/ufs-sysfs.c
> > @@ -1047,6 +1047,86 @@ static inline bool ufshcd_is_wb_attrs(enum
> attr_idn idn)
> >               idn <= QUERY_ATTR_IDN_CURR_WB_BUFF_SIZE;
> >   }
> >
> > +static inline bool ufshcd_is_temp_attrs(enum attr_idn idn)
> > +{
> > +     return idn >= QUERY_ATTR_IDN_CASE_ROUGH_TEMP &&
> > +            idn <= QUERY_ATTR_IDN_LOW_TEMP_BOUND;
> > +}
> 
> Modern compilers are good at deciding when to inline a function so
> please leave out the 'inline' keyword from the above function.
Done.

> 
> > +static bool ufshcd_case_temp_legal(struct ufs_hba *hba)\
> 
> Please use another word than "legal" since the primary meaning of
> "legal" is "of or relating to law".
Done.

> 
> > +     ufshcd_rpm_get_sync(hba);
> > +     ret = ufshcd_query_attr(hba, UPIU_QUERY_OPCODE_READ_ATTR,
> > +                             QUERY_ATTR_IDN_EE_CONTROL, 0, 0, &ee_mask);
> > +     ufshcd_rpm_put_sync(hba);
> 
> Are there any ufshcd_query_attr() calls that are not surrounded by
> ufshcd_rpm_{get,put}_sync()? If not, please move the
> ufshcd_rpm_{get,put}_sync() calls into ufshcd_query_attr().
Will check.

Thanks,
Avri
> 
> Thanks,
> 
> Bart.