linux-kernel - Re: [PATCH] power: supply: remove less-than-zero comparison of unsigned variables

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Message-ID: <SN6PR06MB534244907609468217F4AAFBA5359@SN6PR06MB5342.namprd06.prod.outlook.com>
Date:   Fri, 28 Oct 2022 21:25:09 -0500
From:   Chris Morgan <macromorgan@...mail.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
Cc:     Muhammad Usama Anjum <usama.anjum@...labora.com>,
        kernel@...labora.com, kernel-janitors@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Maya Matuszczyk <maccraft123mc@...il.com>
Subject: Re: [PATCH] power: supply: remove less-than-zero comparison of
 unsigned variables

On Sat, Oct 29, 2022 at 02:17:08AM +0200, Sebastian Reichel wrote:
> Hi,
> 
> On Tue, Oct 04, 2022 at 11:45:21AM +0500, Muhammad Usama Anjum wrote:
> > max_chg_vol_reg and max_chg_cur_reg are unsigned variables. The
> > less-than-zero comparison of an unsigned value is never true. Remove
> > these checks.
> > 
> > Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
> > ---
> 
> I'm a bit hesitant to apply this. While the analysis is correct
> max_chg_cur_reg is sourced from rk817_chg_cur_to_reg(). That has
> has a 'u8' return value as function signature, but tries to return
> -EINVAL. I think it makes sense to either fix this at the same
> time or change the variable type to signed. Also please Cc the
> driver author (done now).

I think this fixes it, can you confirm?

https://lore.kernel.org/linux-pm/20221019234505.5viojwmk6ksqr4gb@mercury.elektranox.org/

Thank you.

> 
> -- Sebastian
> 
> >  drivers/power/supply/rk817_charger.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/power/supply/rk817_charger.c b/drivers/power/supply/rk817_charger.c
> > index 635f051b0821..aa4b33f1bb83 100644
> > --- a/drivers/power/supply/rk817_charger.c
> > +++ b/drivers/power/supply/rk817_charger.c
> > @@ -951,12 +951,12 @@ static int rk817_battery_init(struct rk817_charger *charger,
> >  
> >  	max_chg_cur_reg = rk817_chg_cur_to_reg(max_chg_cur_ma);
> >  
> > -	if (max_chg_vol_reg < 0 || max_chg_vol_reg > 7) {
> > +	if (max_chg_vol_reg > 7) {
> >  		return dev_err_probe(charger->dev, -EINVAL,
> >  		       "invalid max charger voltage, value %u unsupported\n",
> >  		       max_chg_vol_mv * 1000);
> >  	}
> > -	if (max_chg_cur_reg < 0 || max_chg_cur_reg > 7) {
> > +	if (max_chg_cur_reg > 7) {
> >  		return dev_err_probe(charger->dev, -EINVAL,
> >  		       "invalid max charger current, value %u unsupported\n",
> >  		       max_chg_cur_ma * 1000);
> > -- 
> > 2.30.2
> >