> -----Original Message-----
> From: Su Hui <suhui@xxxxxxxxxxxx>
> Sent: Friday, November 24, 2023 10:04 AM
> To: dan.carpenter@xxxxxxxxxx; Ping-Ke Shih <pkshih@xxxxxxxxxxx>; kvalo@xxxxxxxxxx; nathan@xxxxxxxxxx;
> ndesaulniers@xxxxxxxxxx; trix@xxxxxxxxxx
> Cc: Su Hui <suhui@xxxxxxxxxxxx>; lizetao1@xxxxxxxxxx; linville@xxxxxxxxxxxxx; Larry.Finger@xxxxxxxxxxxx;
> linux-wireless@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; llvm@xxxxxxxxxxxxxxx;
> kernel-janitors@xxxxxxxxxxxxxxx
> 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.
