linux-kernel - Re: [PATCH v3] thermal: ti-soc-thermal: Remove unused variable 'val'

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 21 Apr 2021 11:06:01 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Lin Ruizhe <linruizhe@...wei.com>
Cc:     rui.zhang@...el.com, edubezval@...il.com, j-keerthy@...com,
        amitk@...nel.org, radhesh.fadnis@...com, eballetbo@...il.com,
        linux-pm@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] thermal: ti-soc-thermal: Remove unused variable 'val'

On 21/04/2021 10:49, Greg KH wrote:
> On Wed, Apr 21, 2021 at 04:42:56PM +0800, Lin Ruizhe wrote:
>> The variable 'val'in function ti_bandgap_restore_ctxt is
>> the register value of read bandgap registers. This function is to
>> restore the context. But there is no operation on the return value
>> of this register, so this block is redundant. Hulk robot scans this
>> warning.This commit remove the dead code.
>>
>> Reported-by: Hulk Robot <hulkci@...wei.com>
>> Fixes: b87ea759a4cc ("staging: omap-thermal: fix context restore function")
>> Signed-off-by: Lin Ruizhe <linruizhe@...wei.com>
>> ---
>> v3:
>> -Add Fixes tag and more accurate commit message in this patch.
>> v2:
>> -As suggest remove the whole unuesed block in fuction
>>  ti_bandgap_restore_ctxt
>>
>>  drivers/thermal/ti-soc-thermal/ti-bandgap.c | 4 ----
>>  1 file changed, 4 deletions(-)
>>
>> diff --git a/drivers/thermal/ti-soc-thermal/ti-bandgap.c b/drivers/thermal/ti-soc-thermal/ti-bandgap.c
>> index d81af89166d2..684ffb645aa9 100644
>> --- a/drivers/thermal/ti-soc-thermal/ti-bandgap.c
>> +++ b/drivers/thermal/ti-soc-thermal/ti-bandgap.c
>> @@ -1142,14 +1142,10 @@ static int ti_bandgap_restore_ctxt(struct ti_bandgap *bgp)
>>  	for (i = 0; i < bgp->conf->sensor_count; i++) {
>>  		struct temp_sensor_registers *tsr;
>>  		struct temp_sensor_regval *rval;
>> -		u32 val = 0;
>>  
>>  		rval = &bgp->regval[i];
>>  		tsr = bgp->conf->sensors[i].registers;
>>  
>> -		if (TI_BANDGAP_HAS(bgp, COUNTER))
>> -			val = ti_bandgap_readl(bgp, tsr->bgap_counter);
> 
> Are you sure that this hardware does not require this read to happen in
> order for it to work properly?

Yes, initially we had the same concern but we were unable to find
anything specific in the history. The commit mentioned above removed the
user of the 'val' code but without removing this block of code.

When looking at the current code, it really looks like an oversight.

There is nothing in the commit's changelog referring to a need of
reading the counter register but perhaps I'm wrong because I'm not sure
to understand correctly the changelog.

> Lots of hardware does need this, have you tested this?
> 
> thanks,
> 
> greg k-h
> 


-- 
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog