Re: [PATCH] net: wireless: rtlwifi: rtl8192de: hw.c: Cleaning up conjunction always evaluates to false

[Larry Finger]

On 06/07/2014 10:24 AM, Rickard Strandqvist wrote:
> Hi!
>
> Yes, 0x3 was one of the most likely :)
> But wanted someone who knows the code better would be heard.
> All agreed? Then I do a new patch.
>
> Looks like it is the same error in the files below, I'll fix them all them to.
>
> rtl8192cu/hw.c:1363:    if ((bt_msr & 0xfc) == MSR_AP)
> rtl8192ce/hw.c:1209:    if ((bt_msr & 0xfc) == MSR_AP)
> rtl8188ee/hw.c:1234:    if ((bt_msr & 0xfc) == MSR_AP)
> rtl8192de/hw.c:1131:    if ((bt_msr & 0xfc) == MSR_AP)
>
>
> Best regards
> Rickard Strandqvist
>
>
> 2014-06-07 17:02 GMT+02:00 Peter Wu <peter@xxxxxxxxxxxxx>:
> > On Saturday 07 June 2014 16:30:19 Rickard Strandqvist wrote:
> > > Expression '(X & 0xfc) == 0x3' is always false
> >
> > While this is true, I believe that some other mistake is made.
> >
> > > I chose to remove this code, because it will not make any difference.
> > > But obviously it is rather a properly designed if statement that is needed.
> > >
> > > This was partly found using a static code analysis program called cppcheck.
> > >
> > > Signed-off-by: Rickard Strandqvist <rickard_strandqvist@xxxxxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/net/wireless/rtlwifi/rtl8192de/hw.c |    5 +----
> > >   1 file changed, 1 insertion(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/net/wireless/rtlwifi/rtl8192de/hw.c b/drivers/net/wireless/rtlwifi/rtl8192de/hw.c
> > > index 2b08671..a1520d5 100644
> > > --- a/drivers/net/wireless/rtlwifi/rtl8192de/hw.c
> > > +++ b/drivers/net/wireless/rtlwifi/rtl8192de/hw.c
> > > @@ -1128,10 +1128,7 @@ static int _rtl92de_set_media_status(struct ieee80211_hw *hw,
> > >        }
> > >        rtl_write_byte(rtlpriv, REG_CR + 2, bt_msr);
> > >        rtlpriv->cfg->ops->led_control(hw, ledaction);
> > > -     if ((bt_msr & 0xfc) == MSR_AP)
> >
> > If you look a few lines up, then you see that bt_msr is OR-ed with MSR_AP
> > for AP interfaces. The 0xfc should be 0x03, see other drivers for example:
> >
> > rtl8723ae/hw.c:1112:    if ((bt_msr & 0x03) == MSR_AP)
> > rtl8723be/hw.c:1200:    if ((bt_msr & 0x03) == MSR_AP)
> > rtl8192cu/hw.c:1363:    if ((bt_msr & 0xfc) == MSR_AP)
> > rtl8192ce/hw.c:1209:    if ((bt_msr & 0xfc) == MSR_AP)
> > rtl8188ee/hw.c:1234:    if ((bt_msr & 0xfc) == MSR_AP)
> > rtl8192de/hw.c:1131:    if ((bt_msr & 0xfc) == MSR_AP)
> >
> > > -             rtl_write_byte(rtlpriv, REG_BCNTCFG + 1, 0x00);
> > > -     else
> > > -             rtl_write_byte(rtlpriv, REG_BCNTCFG + 1, 0x66);
> > > +     rtl_write_byte(rtlpriv, REG_BCNTCFG + 1, 0x66);
> > >        return 0;
> > >   }

Peter,

As you have learned here, automatically making changes suggested by some tool 
may convert a visible bug into one that is invisible, and only found by a 
detailed line-by-line examination of the code, and that is unlikely to happen. 
Please be careful.

From everything I see, the test in all drivers should be

	if ((bt_msr & MSR_AP) == MSR_AP)

Larry

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