linux-kernel - Re: drivers/staging/rtlwifi/base.c:920:7-9: WARNING: possible condition with no effect (if == else)

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Message-ID: <9449a43b-2e02-f326-f5b1-7a55852ccb5b@lwfinger.net>
Date:   Fri, 13 Oct 2017 13:11:20 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kbuild-all@...org
Subject: Re: drivers/staging/rtlwifi/base.c:920:7-9: WARNING: possible
 condition with no effect (if == else)

Julia,

On 10/13/2017 08:55 AM, Julia Lawall wrote:
> It seems that the then and else branches of the conditions on lines 920
> and 932 are the same.

I think line 923 should be using RTL_RC_VHT_RATE_2SS_MCS8 rather than 
RTL_RC_VHT_RATE_2SS_MCS9, but I have sent an inquiry to my contact at Realtek to 
check.

Thanks,

Larry

> On Fri, 13 Oct 2017, kbuild test robot wrote:
> 
>> CC: kbuild-all@...org
>> CC: linux-kernel@...r.kernel.org
>> TO: Larry Finger <Larry.Finger@...inger.net>
>> CC: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
>>
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head:   3d7882769b5dc929690f96e0c318c29b97f51018
>> commit: 5b5ab4cb5cda824ef59e0511ac5d585f35f1a1a6 staging: r8822be: Add Makefiles and Kconfig for new driver
>> date:   8 weeks ago
>> :::::: branch date: 12 hours ago
>> :::::: commit date: 8 weeks ago
>>
>>>> drivers/staging/rtlwifi/base.c:920:7-9: WARNING: possible condition with no effect (if == else)
>>     drivers/staging/rtlwifi/base.c:932:7-9: WARNING: possible condition with no effect (if == else)
>>
>> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5b5ab4cb5cda824ef59e0511ac5d585f35f1a1a6
>> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>> git remote update linus
>> git checkout 5b5ab4cb5cda824ef59e0511ac5d585f35f1a1a6
>> vim +920 drivers/staging/rtlwifi/base.c
>>
>> 56bde846 Ping-Ke Shih 2017-08-17  905
>> 56bde846 Ping-Ke Shih 2017-08-17  906  static u8 _rtl_get_vht_highest_n_rate(struct ieee80211_hw *hw,
>> 56bde846 Ping-Ke Shih 2017-08-17  907  				      struct ieee80211_sta *sta)
>> 56bde846 Ping-Ke Shih 2017-08-17  908  {
>> 56bde846 Ping-Ke Shih 2017-08-17  909  	struct rtl_priv *rtlpriv = rtl_priv(hw);
>> 56bde846 Ping-Ke Shih 2017-08-17  910  	struct rtl_phy *rtlphy = &rtlpriv->phy;
>> 56bde846 Ping-Ke Shih 2017-08-17  911  	u8 hw_rate;
>> 56bde846 Ping-Ke Shih 2017-08-17  912  	u16 tx_mcs_map = le16_to_cpu(sta->vht_cap.vht_mcs.tx_mcs_map);
>> 56bde846 Ping-Ke Shih 2017-08-17  913
>> 56bde846 Ping-Ke Shih 2017-08-17  914  	if ((get_rf_type(rtlphy) == RF_2T2R) &&
>> 56bde846 Ping-Ke Shih 2017-08-17  915  	    (tx_mcs_map & 0x000c) != 0x000c) {
>> 56bde846 Ping-Ke Shih 2017-08-17  916  		if ((tx_mcs_map & 0x000c) >> 2 ==
>> 56bde846 Ping-Ke Shih 2017-08-17  917  			IEEE80211_VHT_MCS_SUPPORT_0_7)
>> 56bde846 Ping-Ke Shih 2017-08-17  918  			hw_rate =
>> 56bde846 Ping-Ke Shih 2017-08-17  919  			rtlpriv->cfg->maps[RTL_RC_VHT_RATE_2SS_MCS7];
>> 56bde846 Ping-Ke Shih 2017-08-17 @920  		else if ((tx_mcs_map  & 0x000c) >> 2 ==
>> 56bde846 Ping-Ke Shih 2017-08-17  921  			IEEE80211_VHT_MCS_SUPPORT_0_8)
>> 56bde846 Ping-Ke Shih 2017-08-17  922  			hw_rate =
>> 56bde846 Ping-Ke Shih 2017-08-17  923  			rtlpriv->cfg->maps[RTL_RC_VHT_RATE_2SS_MCS9];
>> 56bde846 Ping-Ke Shih 2017-08-17  924  		else
>> 56bde846 Ping-Ke Shih 2017-08-17  925  			hw_rate =
>> 56bde846 Ping-Ke Shih 2017-08-17  926  			rtlpriv->cfg->maps[RTL_RC_VHT_RATE_2SS_MCS9];
>> 56bde846 Ping-Ke Shih 2017-08-17  927  	} else {
>> 56bde846 Ping-Ke Shih 2017-08-17  928  		if ((tx_mcs_map  & 0x0003) ==
>> 56bde846 Ping-Ke Shih 2017-08-17  929  			IEEE80211_VHT_MCS_SUPPORT_0_7)
>> 56bde846 Ping-Ke Shih 2017-08-17  930  			hw_rate =
>> 56bde846 Ping-Ke Shih 2017-08-17  931  			rtlpriv->cfg->maps[RTL_RC_VHT_RATE_1SS_MCS7];
>> 56bde846 Ping-Ke Shih 2017-08-17  932  		else if ((tx_mcs_map  & 0x0003) ==
>> 56bde846 Ping-Ke Shih 2017-08-17  933  			IEEE80211_VHT_MCS_SUPPORT_0_8)
>> 56bde846 Ping-Ke Shih 2017-08-17  934  			hw_rate =
>> 56bde846 Ping-Ke Shih 2017-08-17  935  			rtlpriv->cfg->maps[RTL_RC_VHT_RATE_1SS_MCS9];
>> 56bde846 Ping-Ke Shih 2017-08-17  936  		else
>> 56bde846 Ping-Ke Shih 2017-08-17  937  			hw_rate =
>> 56bde846 Ping-Ke Shih 2017-08-17  938  			rtlpriv->cfg->maps[RTL_RC_VHT_RATE_1SS_MCS9];
>> 56bde846 Ping-Ke Shih 2017-08-17  939  	}
>> 56bde846 Ping-Ke Shih 2017-08-17  940
>> 56bde846 Ping-Ke Shih 2017-08-17  941  	return hw_rate;
>> 56bde846 Ping-Ke Shih 2017-08-17  942  }
>> 56bde846 Ping-Ke Shih 2017-08-17  943
>>
>> :::::: The code at line 920 was first introduced by commit
>> :::::: 56bde846304ea05d5f8c8de0e3a42627a7a92be6 staging: r8822be: Add existing rtlwifi and rtl_pci parts for new driver
>>
>> :::::: TO: Ping-Ke Shih <pkshih@...ltek.com>
>> :::::: CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>
>> ---
>> 0-DAY kernel test infrastructure                Open Source Technology Center
>> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
>>
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