linux-kernel - RE: [PATCH wireless-next 01/11] wifi: rtlwifi: add calculate_bit

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Date: Wed, 20 Dec 2023 06:47:51 +0000
From: Ping-Ke Shih <pkshih@...ltek.com>
To: Su Hui <suhui@...china.com>, "kvalo@...nel.org" <kvalo@...nel.org>
CC: "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: RE: [PATCH wireless-next 01/11] wifi: rtlwifi: add calculate_bit_shift()



> -----Original Message-----
> From: Su Hui <suhui@...china.com>
> Sent: Tuesday, December 19, 2023 2:57 PM
> To: Ping-Ke Shih <pkshih@...ltek.com>; kvalo@...nel.org
> Cc: Su Hui <suhui@...china.com>; linux-wireless@...r.kernel.org; linux-kernel@...r.kernel.org;
> kernel-janitors@...r.kernel.org
> Subject: [PATCH wireless-next 01/11] wifi: rtlwifi: add calculate_bit_shift()
> 
> There are many same functions like _rtl88e_phy_calculate_bit_shift(),
> _rtl92c_phy_calculate_bit_shift() and so on. And these functions can
> cause undefined bitwise shift behavior. Add calculate_bit_shift() to
> replace them and fix undefined behavior in subsequent patches.
> 
> Signed-off-by: Su Hui <suhui@...china.com>

Acked-by: Ping-Ke Shih <pkshih@...ltek.com>

> ---
>  drivers/net/wireless/realtek/rtlwifi/wifi.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/wifi.h b/drivers/net/wireless/realtek/rtlwifi/wifi.h
> index 31a481f43a07..5d842cc394aa 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/wifi.h
> +++ b/drivers/net/wireless/realtek/rtlwifi/wifi.h
> @@ -3069,4 +3069,11 @@ static inline struct ieee80211_sta *rtl_find_sta(struct ieee80211_hw *hw,
>         return ieee80211_find_sta(mac->vif, mac_addr);
>  }
> 
> +static inline u32 calculate_bit_shift(u32 bitmask)
> +{
> +       if (WARN_ON_ONCE(!bitmask))
> +               return 0;
> +
> +       return __ffs(bitmask);
> +}
>  #endif

Basically, this patchset is to change from below example to above one. 

static u32 _rtl92d_phy_calculate_bit_shift(u32 bitmask)
{
       u32 i = ffs(bitmask);

       return i ? i - 1 : 32;
}

And, bitmask is expected not 0, so all are fine to me. 
(I don't reply all patches one-by-one to bother people)

Ping-Ke