linux-kernel - Re: [PATCH v6] staging: vt6656: add error code handling to unused variable

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Message-ID: <61bb6678d48557895671488357a62680d0ae655f.camel@gmail.com>
Date:   Mon, 30 Mar 2020 15:26:04 -0700
From:   "John B. Wyatt IV" <jbwyatt4@...il.com>
To:     Stefano Brivio <sbrivio@...hat.com>
Cc:     outreachy-kernel@...glegroups.com,
        Julia Lawall <julia.lawall@...ia.fr>,
        Forest Bond <forest@...ttletooquiet.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Quentin Deslandes <quentin.deslandes@...ev.co.uk>,
        Colin Ian King <colin.king@...onical.com>,
        Malcolm Priestley <tvboxspy@...il.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] staging: vt6656: add error code handling to unused
 variable

On Tue, 2020-03-31 at 00:01 +0200, Stefano Brivio wrote:
> On Mon, 30 Mar 2020 14:46:13 -0700
> "John B. Wyatt IV" <jbwyatt4@...il.com> wrote:
> 
> > Add error code handling to unused 'ret' variable that was never
> > used.
> > Return an error code from functions called within
> > vnt_radio_power_on.
> > 
> > Issue reported by coccinelle (coccicheck).
> > 
> > Suggested-by: Quentin Deslandes <quentin.deslandes@...ev.co.uk>
> > Suggested-by: Stefano Brivio <sbrivio@...hat.com>
> > Reviewed-by: Quentin Deslandes <quentin.deslandes@...ev.co.uk>
> > Signed-off-by: John B. Wyatt IV <jbwyatt4@...il.com>
> > ---
> > v6: Forgot to add all the v5 code to commit.
> > 
> > v5: Remove Suggested-by: Julia Lawall above seperator line.
> > 	Remove break; statement in switch block.
> > 	break; removal checked by both gcc compile and checkpatch.
> > 	Suggested by Stefano Brivio <sbrivio@...hat.com>
> > 
> > v4: Move Suggested-by: Julia Lawall above seperator line.
> >     Add Reviewed-by tag as requested by Quentin Deslandes.
> > 
> > v3: Forgot to add v2 code changes to commit.
> > 
> > v2: Replace goto statements with return.
> >     Remove last if check because it was unneeded.
> >     Suggested-by: Julia Lawall <julia.lawall@...ia.fr>
> > 
> >  drivers/staging/vt6656/card.c | 20 ++++++++++++--------
> >  1 file changed, 12 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/staging/vt6656/card.c
> > b/drivers/staging/vt6656/card.c
> > index dc3ab10eb630..c947e8188384 100644
> > --- a/drivers/staging/vt6656/card.c
> > +++ b/drivers/staging/vt6656/card.c
> > @@ -723,9 +723,13 @@ int vnt_radio_power_on(struct vnt_private
> > *priv)
> >  {
> >  	int ret = 0;
> >  
> > -	vnt_exit_deep_sleep(priv);
> > +	ret = vnt_exit_deep_sleep(priv);
> > +	if (ret)
> > +		return ret;
> >  
> > -	vnt_mac_reg_bits_on(priv, MAC_REG_HOSTCR, HOSTCR_RXON);
> > +	ret = vnt_mac_reg_bits_on(priv, MAC_REG_HOSTCR, HOSTCR_RXON);
> > +	if (ret)
> > +		return ret;
> >  
> >  	switch (priv->rf_type) {
> >  	case RF_AL2230:
> > @@ -734,14 +738,14 @@ int vnt_radio_power_on(struct vnt_private
> > *priv)
> >  	case RF_VT3226:
> >  	case RF_VT3226D0:
> >  	case RF_VT3342A0:
> > -		vnt_mac_reg_bits_on(priv, MAC_REG_SOFTPWRCTL,
> > -				    (SOFTPWRCTL_SWPE2 |
> > SOFTPWRCTL_SWPE3));
> > -		break;
> > +		ret = vnt_mac_reg_bits_on(priv, MAC_REG_SOFTPWRCTL,
> > +					  (SOFTPWRCTL_SWPE2 | 
> > +					  SOFTPWRCTL_SWPE3));
> >  	}
> > +	if (ret)
> > +		return ret;
> 
> Hmm, sorry, I haven't been clear enough I guess.
> 
> This is what you're doing:
> 
> if rf_type is not in that list:
> - set some bits in a register
> - did it fail? return
> - did it fail? return
> ...
> 
> if rf_type is in that list:
> - set some bits in a register
> - did it fail? return
> - set some other bits
> - did it fail? return
> ...
> 
> Now, the "set some other bits" part is already selected depending on
> rf_type. There's no need to check 'ret' otherwise, so you can move
> the
> return just after setting 'ret', in the switch case.
> 

Thank you for pointing that out Stefano. That would be a serious issue
with logic.

Just to be sure. Are you looking for this?

switch (priv->rf_type) {
case RF_AL2230:
case RF_AL2230S:
case RF_AIROHA7230:
case RF_VT3226:
case RF_VT3226D0:
case RF_VT3342A0:
	ret = vnt_mac_reg_bits_on(priv, MAC_REG_SOFTPWRCTL,
				  (SOFTPWRCTL_SWPE2 | 
				  SOFTPWRCTL_SWPE3));
	if (ret)
		return ret;
}

> With a check, because you don't want to return if ret == 0.
> 

What do you mean exactly by this?

The new code should only return a 0 at the end of the function with the
vnt_mac_reg_bits_off call.