Re: [PATCH v2 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior

[Su Hui]

On 2023/11/24 16:51, Ping-Ke Shih wrote:
> Subject: [PATCH v2 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior
>
> [...]
> > diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
> > b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
> > index 6df270e29e66..52ab1b0761c0 100644
> > --- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
> > +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
> > @@ -31,7 +31,12 @@ static u32 _rtl8821ae_phy_calculate_bit_shift(u32 bitmask)
> >   {
> >          u32 i = ffs(bitmask);
> >
> > -       return i ? i - 1 : 32;
> > +       if (!i) {
> > +               WARN_ON_ONCE(1);
> > +               return 0;
> > +       }
> > +
> > +       return i - 1;
> >   }
> Personally, I prefer to use __ffs(), because in normal case no need additional '-1',
> and abnormal cases should not happen.

Hi,  Ping-Ke

Replace _rtl8821ae_phy_calculate_bit_shift() by __ffs(bitmask) is better,
but I'm not sure what callers should do when callers check bitmask is 0 before calling.
Maybe this check is useless?

I can send a v3 patch if using  __ffs(bitmask) and no check for bitmask is fine.
Or could you send this patch if you have a better idea?
Thanks for your suggestion!

Su Hui