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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
Date:   Tue, 17 May 2022 09:53:23 +0800
Message-ID: <CAAd53p57APcectWW-NN_=HE6JkTQRk717cWNZ5iJcP+MtEYjog@mail.gmail.com>
Subject: Re: [PATCH] misc: rtsx: Set setting_reg2 before use.
To:     Tom Rix <trix@redhat.com>
Cc:     Nathan Chancellor <nathan@kernel.org>, arnd@arndb.de,
        gregkh@linuxfoundation.org, ndesaulniers@google.com,
        ricky_wu@realtek.com, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev
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On Tue, May 17, 2022 at 1:06 AM Tom Rix <trix@redhat.com> wrote:
>
>
> On 5/16/22 8:56 AM, Nathan Chancellor wrote:
> > On Mon, May 16, 2022 at 09:00:47AM -0400, Tom Rix wrote:
> >> The clang build fails with
> >> rts5261.c:406:13: error: variable 'setting_reg2' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> >>          } else if (efuse_valid == 0) {
> >>                     ^~~~~~~~~~~~~~~~
> >>
> >> setting_reg2 is set in this block
> >>    if (efuse_valid == 2 || efuse_valid == 3) {
> >> ..
> >>    } else if (efuse_valid == 0) {
> >>      // default
> >> ..
> >>    }
> >> But efuse_valid can also have a value of 1.
> >> Change the 'else if' to 'else' to make the second block the default.
> >>
> >> Fixes: b1c5f3085149 ("misc: rtsx: add rts5261 efuse function")
> >> Signed-off-by: Tom Rix <trix@redhat.com>
> > I am not sure if this fix is correct from a functional standpoint (i.e.
> > is treating efuse_valid == 1 the same as efuse_valid == 0 correct?) but
> > it is better than not handling this value altogether. For what it's
> > worth:
>
> I looked at how the code used to work, this seemed better than
> initializing to NULL.

Or maybe use a single if block?

u16 setting_reg1 =PCR_SETTING_REG1 , setting_reg2 = PCR_SETTING_REG2;
...
if ((efuse_valid == 2 || efuse_valid == 3) && (valid != 3) {
    setting_reg1 = PCR_SETTING_REG4;
    setting_reg2 = PCR_SETTING_REG5;
}

Kai-Heng

>
> >
> > Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> >
> > As a side note, it is unfortunate that this change made it into -next
> > when there was an outstanding report about this warning:
>
>  From the clang side, this is a build break and my static analysis infra
> goes down.
>
> These build breaks seem to happening every week, is there a precommit
> clang gating test that could be done for -next ?
>
> Tom
>
> >
> > https://lore.kernel.org/202205100220.WyAyhKap-lkp@intel.com/
> >
> >> ---
> >>   drivers/misc/cardreader/rts5261.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/misc/cardreader/rts5261.c b/drivers/misc/cardreader/rts5261.c
> >> index 749cc5a46d13..f22634b14dc8 100644
> >> --- a/drivers/misc/cardreader/rts5261.c
> >> +++ b/drivers/misc/cardreader/rts5261.c
> >> @@ -403,7 +403,7 @@ static void rts5261_init_from_hw(struct rtsx_pcr *pcr)
> >>                      setting_reg1 = PCR_SETTING_REG4;
> >>                      setting_reg2 = PCR_SETTING_REG5;
> >>              }
> >> -    } else if (efuse_valid == 0) {
> >> +    } else {
> >>              // default
> >>              setting_reg1 = PCR_SETTING_REG1;
> >>              setting_reg2 = PCR_SETTING_REG2;
> >> --
> >> 2.27.0
> >>
> > Cheers,
> > Nathan
> >
>