Negative value returns for sensor in tiogapass

Jayashree D jayashree-d at hcl.com
Tue Mar 2 17:16:33 AEDT 2021


Classification: Confidential

Thanks Ed for your response.
I'll look into the specs.

-----Original Message-----
From: Ed Tanous <edtanous at google.com> 
Sent: Friday, February 26, 2021 9:57 PM
To: Jayashree D <jayashree-d at hcl.com>
Cc: openbmc at lists.ozlabs.org
Subject: Re: Negative value returns for sensor in tiogapass

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On Fri, Feb 26, 2021 at 12:55 AM Jayashree D <jayashree-d at hcl.com> wrote:
>
> Classification: Public
>
> Hi Team,
>
>
>
> Recently, I have tested sensors for tiogapass, in which one sensor returns negative value.
>
> After analysing the code in the dbus-sensors repo, I found the following issue.
>
>
>
> dbus-sensors/IpmbSensor.cpp at master · openbmc/dbus-sensors 
> (github.com)
>
>
>
> From the above link, We need only below line in the code to process the HSC sensors value for tiogapass.
>
>
>
> int16_t value = ((data[4] << 8) | data[3]);
>
>
>
> Since the below logic is added, the values get shifted and getting negative values as output.
>
>
>
> constexpr const size_t shift = 16 - 11; // 11bit into 16bit
>
> value <<= shift;
>
> value >>= shift;
>
>
>
> Could you please suggest any idea to resolve this issue.

I haven't looked at this in detail, but we should follow whatever the spec says here.  If whomever wrote this originally put in the wrong math (which seems likely, given they were implementing 4 types and probably only using one) then we should just get it fixed and do what the spec says.

>
>
>
> Regards,
>
> Jayashree
>
>
>
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