[PATCH wireless-next v3 1/2] wifi: rtlwifi: rtl8821ae: phy: remove some useless code

[PATCH wireless-next v3 1/2] wifi: rtlwifi: rtl8821ae: phy: remove some useless code

[Su Hui]

Clang static checker warning:
Value stored to 'v1' is never read [deadcode.DeadStores]
Value stored to 'channel' is never read [deadcode.DeadStores]

Remove them to save some place.

Signed-off-by: Su Hui <suhui@nfschina.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
---
v3: 
 - same as v2.
v2:
 - fix the subject prefix problem

 drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
index 5323ead30db0..6df270e29e66 100644
--- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
@@ -2038,15 +2038,9 @@ static bool _rtl8821ae_phy_config_bb_with_pgheaderfile(struct ieee80211_hw *hw,
 			 /*don't need the hw_body*/
 			if (!_rtl8821ae_check_condition(hw, v1)) {
 				i += 2; /* skip the pair of expression*/
-				v1 = array[i];
 				v2 = array[i+1];
-				v3 = array[i+2];
-				while (v2 != 0xDEAD) {
+				while (v2 != 0xDEAD)
 					i += 3;
-					v1 = array[i];
-					v2 = array[i+1];
-					v3 = array[i+2];
-				}
 			}
 		}
 	}
@@ -3543,7 +3537,6 @@ u8 rtl8821ae_phy_sw_chnl(struct ieee80211_hw *hw)
 	struct rtl_phy *rtlphy = &rtlpriv->phy;
 	struct rtl_hal *rtlhal = rtl_hal(rtl_priv(hw));
 	u32 timeout = 1000, timecount = 0;
-	u8 channel = rtlphy->current_channel;
 
 	if (rtlphy->sw_chnl_inprogress)
 		return 0;
@@ -3566,8 +3559,6 @@ u8 rtl8821ae_phy_sw_chnl(struct ieee80211_hw *hw)
 		rtl8821ae_phy_switch_wirelessband(hw, BAND_ON_2_4G);
 
 	rtlphy->sw_chnl_inprogress = true;
-	if (channel == 0)
-		channel = 1;
 
 	rtl_dbg(rtlpriv, COMP_SCAN, DBG_TRACE,
 		"switch to channel%d, band type is %d\n",
-- 
2.30.2

[PATCH wireless-next v3 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior

[Su Hui]

Clang staic checker warning:
drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c:184:49:
	The result of the left shift is undefined due to shifting by '32',
	which is greater or equal to the width of type 'u32'.
	[core.UndefinedBinaryOperatorResult]

If the value of the right operand is negative or is greater than or
equal to the width of the promoted left operand, the behavior is
undefined.[1][2]

For example, when using different gcc's compilation optimizaation options
(-O0 or -O2), the result of '(u32)data << 32' is different. One is 0, the
other is old value of data. Let _rtl8821ae_phy_calculate_bit_shift()'s
return value less than 32 to fix this problem. Warn if bitmask is zero.

[1]:https://stackoverflow.com/questions/11270492/what-does-the-c-
standard-say-about-bitshifting-more-bits-than-the-width-of-type
[2]:https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

Fixes: 21e4b0726dc6 ("rtlwifi: rtl8821ae: Move driver from staging to regular tree")
Signed-off-by: Su Hui <suhui@nfschina.com>
---
v3:
 - use __ffs() and make code briefer. (Thanks to Ping-Ke)

v2:
 - fix the subject prefix problem
 - silence the warning by not return 32 bits rather than adding a type cast.(Thanks to Dan and Ping-Ke)

 drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
index 6df270e29e66..68c3fb0395ce 100644
--- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
@@ -29,9 +29,10 @@ static void _rtl8821ae_phy_rf_serial_write(struct ieee80211_hw *hw,
 					   u32 data);
 static u32 _rtl8821ae_phy_calculate_bit_shift(u32 bitmask)
 {
-	u32 i = ffs(bitmask);
+	if (WARN_ON_ONCE(!bitmask))
+		return 0;
 
-	return i ? i - 1 : 32;
+	return __ffs(bitmask);
 }
 static bool _rtl8821ae_phy_bb8821a_config_parafile(struct ieee80211_hw *hw);
 /*static bool _rtl8812ae_phy_config_mac_with_headerfile(struct ieee80211_hw *hw);*/
-- 
2.30.2

RE: [PATCH wireless-next v3 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior

[Ping-Ke Shih]

> -----Original Message-----
> From: Su Hui <suhui@nfschina.com>
> Sent: Monday, November 27, 2023 9:35 AM
> To: Ping-Ke Shih <pkshih@realtek.com>; dan.carpenter@linaro.org; kvalo@kernel.org; nathan@kernel.org;
> ndesaulniers@google.com; trix@redhat.com
> Cc: Su Hui <suhui@nfschina.com>; lizetao1@huawei.com; linville@tuxdriver.com; Larry.Finger@lwfinger.net;
> linux-wireless@vger.kernel.org; linux-kernel@vger.kernel.org; llvm@lists.linux.dev;
> kernel-janitors@vger.kernel.org
> Subject: [PATCH wireless-next v3 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior
> 
> Clang staic checker warning:
> drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c:184:49:
>         The result of the left shift is undefined due to shifting by '32',
>         which is greater or equal to the width of type 'u32'.
>         [core.UndefinedBinaryOperatorResult]
> 
> If the value of the right operand is negative or is greater than or
> equal to the width of the promoted left operand, the behavior is
> undefined.[1][2]
> 
> For example, when using different gcc's compilation optimizaation options
> (-O0 or -O2), the result of '(u32)data << 32' is different. One is 0, the
> other is old value of data. Let _rtl8821ae_phy_calculate_bit_shift()'s
> return value less than 32 to fix this problem. Warn if bitmask is zero.
> 
> [1]:https://stackoverflow.com/questions/11270492/what-does-the-c-
> standard-say-about-bitshifting-more-bits-than-the-width-of-type
> [2]:https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf
> 
> Fixes: 21e4b0726dc6 ("rtlwifi: rtl8821ae: Move driver from staging to regular tree")
> Signed-off-by: Su Hui <suhui@nfschina.com>

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

> +       if (WARN_ON_ONCE(!bitmask))

I test this patch with real hardware to connect 2GHz and 5GHz AP
respectively and keep ping for a while. It doesn't throw warning
by this statement. 

Re: [wireless-next,v3,1/2] wifi: rtlwifi: rtl8821ae: phy: remove some useless code

[Kalle Valo]

Su Hui <suhui@nfschina.com> wrote:

> Clang static checker warns:
> 
> Value stored to 'v1' is never read [deadcode.DeadStores]
> Value stored to 'channel' is never read [deadcode.DeadStores]
> 
> Remove them to save some place.
> 
> Signed-off-by: Su Hui <suhui@nfschina.com>
> Acked-by: Ping-Ke Shih <pkshih@realtek.com>

2 patches applied to wireless-next.git, thanks.

cda37445718d wifi: rtlwifi: rtl8821ae: phy: remove some useless code
bc8263083af6 wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20231127013511.26694-1-suhui@nfschina.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches