linux-kernel - Re: [PATCH] scsi: ufs-mediatek: Avoid using ret uninitialized in ufs_mtk_setup

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Message-ID: <1553124216.30977.80.camel@mtkswgap22>
Date:   Thu, 21 Mar 2019 07:23:36 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     Nathan Chancellor <natechancellor@...il.com>
CC:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        <linux-scsi@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <clang-built-linux@...glegroups.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] scsi: ufs-mediatek: Avoid using ret uninitialized in
 ufs_mtk_setup_clocks

Hi,

On Wed, 2019-03-20 at 15:23 -0700, Nick Desaulniers wrote:
> On Wed, Mar 20, 2019 at 11:06 AM Nathan Chancellor
> <natechancellor@...il.com> wrote:
> >
> > When building with -Wsometimes-uninitialized, Clang warns:
> >
> > drivers/scsi/ufs/ufs-mediatek.c:112:7: warning: variable 'ret' is used
> > uninitialized whenever 'if' condition is false
> > [-Wsometimes-uninitialized]
> >                 if (on)
> >                     ^~
> > drivers/scsi/ufs/ufs-mediatek.c:120:9: note: uninitialized use occurs
> > here
> >         return ret;
> >                ^~~
> > drivers/scsi/ufs/ufs-mediatek.c:112:3: note: remove the 'if' if its
> > condition is always true
> >                 if (on)
> >                 ^~~~~~~
> > drivers/scsi/ufs/ufs-mediatek.c:108:7: warning: variable 'ret' is used
> > uninitialized whenever 'if' condition is false
> > [-Wsometimes-uninitialized]
> >                 if (!on)
> >                     ^~~
> > drivers/scsi/ufs/ufs-mediatek.c:120:9: note: uninitialized use occurs
> > here
> >         return ret;
> >                ^~~
> > drivers/scsi/ufs/ufs-mediatek.c:108:3: note: remove the 'if' if its
> > condition is always true
> >                 if (!on)
> >                 ^~~~~~~~
> > drivers/scsi/ufs/ufs-mediatek.c:96:9: note: initialize the variable
> > 'ret' to silence this warning
> >         int ret;
> >                ^
> >                 = 0
> > 2 warnings generated.
> >
> > Remove the default case and initialize ret to -EINVAL to properly fix
> > this warning.
> >
> > Fixes: ddd90623ce26 ("scsi: ufs-mediatek: Add UFS support for Mediatek SoC chips")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/426
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >  drivers/scsi/ufs/ufs-mediatek.c | 5 +----
> >  1 file changed, 1 insertion(+), 4 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufs-mediatek.c b/drivers/scsi/ufs/ufs-mediatek.c
> > index c3b78fc83d3f..34aecad04468 100644
> > --- a/drivers/scsi/ufs/ufs-mediatek.c
> > +++ b/drivers/scsi/ufs/ufs-mediatek.c
> > @@ -93,7 +93,7 @@ static int ufs_mtk_setup_clocks(struct ufs_hba *hba, bool on,
> >                                 enum ufs_notify_change_status status)
> >  {
> >         struct ufs_mtk_host *host = ufshcd_get_variant(hba);
> > -       int ret;
> > +       int ret = -EINVAL;
> >
> >         /*
> >          * In case ufs_mtk_init() is not yet done, simply ignore.
> > @@ -112,9 +112,6 @@ static int ufs_mtk_setup_clocks(struct ufs_hba *hba, bool on,
> >                 if (on)
> >                         ret = phy_power_on(host->mphy);
> >                 break;
> > -       default:
> > -               ret = -EINVAL;
> > -               break;
> >         }
> >
> >         return ret;
> > --
> > 2.21.0
> >
> 
> The enum being switched on (enum ufs_notify_change_status) only has 2
> values; so the default case is impossible.  A switch is probably
> overkill, but this change is fine as is.  Thanks for sending it.
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

Currently the caller is always using "on" with "POST_CHANGE" and "!on"
with "PRE_CHANGE", however the warnings shall be fixed. Thanks for
fixing it.

Reviewed-by: Stanley Chu <stanley.chu@...iatek.com>