netdev - RE: [PATCH] rtlwifi: rtl8192se: remove redundant rtl_get

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Date:   Tue, 6 Dec 2022 02:01:58 +0000
From:   Ping-Ke Shih <pkshih@...ltek.com>
To:     Peter Kosyh <pkosyh@...dex.ru>
CC:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Kalle Valo <kvalo@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>
Subject: RE: [PATCH] rtlwifi: rtl8192se: remove redundant rtl_get_bbreg call


> -----Original Message-----
> From: Peter Kosyh <pkosyh@...dex.ru>
> Sent: Monday, December 5, 2022 4:54 PM
> To: Ping-Ke Shih <pkshih@...ltek.com>
> Cc: Peter Kosyh <pkosyh@...dex.ru>; David S. Miller <davem@...emloft.net>; Eric Dumazet
> <edumazet@...gle.com>; Kalle Valo <kvalo@...nel.org>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
> <pabeni@...hat.com>; linux-wireless@...r.kernel.org; netdev@...r.kernel.org;
> linux-kernel@...r.kernel.org; lvc-project@...uxtesting.org
> Subject: [PATCH] rtlwifi: rtl8192se: remove redundant rtl_get_bbreg call
> 
> Extra rtl_get_bbreg looks like redundant reading. The read has
> already been done in the "else" branch. Compile test only.

Originally, the code is 

01 if (rfpi_enable)
02     val = get_from_interface_A();
03 else
04    val = get_from_interface_B();
05
06 val = get_from_interface_B();

This patch is to remove line 06, and it looks like logic is changed. However,
'rfpi_enable' is decided by 0x820[8] and 0x828[8] set by rtl8192sephy_reg_2t2rarray[]
table, and 'rfpi_enable' is always false. I think this is why nobody can't
encounter problem and find this bug.

> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Peter Kosyh <pkosyh@...dex.ru>

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

> ---
> If this code is important for the operation of the hardware, then it would
> be nice to comment on it.
> 
>  drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> b/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> index aaa004d4d6d0..09591a0b5a81 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> @@ -115,9 +115,6 @@ static u32 _rtl92s_phy_rf_serial_read(struct ieee80211_hw *hw,
>  		retvalue = rtl_get_bbreg(hw, pphyreg->rf_rb,
>  					 BLSSI_READBACK_DATA);
> 
> -	retvalue = rtl_get_bbreg(hw, pphyreg->rf_rb,
> -				 BLSSI_READBACK_DATA);
> -
>  	rtl_dbg(rtlpriv, COMP_RF, DBG_TRACE, "RFR-%d Addr[0x%x]=0x%x\n",
>  		rfpath, pphyreg->rf_rb, retvalue);
> 
> --
> 2.38.1