linux-kernel - [PATCH] staging: wlan-ng: Avoid bitwise vs logical OR warning in hfa384x_usb

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Message-Id: <20211014215703.3705371-1-nathan@kernel.org>
Date:   Thu, 14 Oct 2021 14:57:03 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] staging: wlan-ng: Avoid bitwise vs logical OR warning in hfa384x_usb_throttlefn()

A new warning in clang points out a place in this file where a bitwise
OR is being used with boolean expressions:

In file included from drivers/staging/wlan-ng/prism2usb.c:2:
drivers/staging/wlan-ng/hfa384x_usb.c:3787:7: warning: use of bitwise '|' with boolean operands [-Wbitwise-instead-of-logical]
            ((test_and_clear_bit(THROTTLE_RX, &hw->usb_flags) &&
            ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/staging/wlan-ng/hfa384x_usb.c:3787:7: note: cast one or both operands to int to silence this warning
1 warning generated.

The comment explains that short circuiting here is undesirable, as the
calls to test_and_{clear,set}_bit() need to happen for both sides of the
expression.

Clang's suggestion would work to silence the warning but the readability
of the expression would suffer even more. To clean up the warning and
make the block more readable, use a variable for each side of the
bitwise expression.

Link: https://github.com/ClangBuiltLinux/linux/issues/1478
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/staging/wlan-ng/hfa384x_usb.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/wlan-ng/hfa384x_usb.c b/drivers/staging/wlan-ng/hfa384x_usb.c
index 59aa84d1837d..938e11a1a0b6 100644
--- a/drivers/staging/wlan-ng/hfa384x_usb.c
+++ b/drivers/staging/wlan-ng/hfa384x_usb.c
@@ -3778,18 +3778,18 @@ static void hfa384x_usb_throttlefn(struct timer_list *t)
 
 	spin_lock_irqsave(&hw->ctlxq.lock, flags);
 
-	/*
-	 * We need to check BOTH the RX and the TX throttle controls,
-	 * so we use the bitwise OR instead of the logical OR.
-	 */
 	pr_debug("flags=0x%lx\n", hw->usb_flags);
-	if (!hw->wlandev->hwremoved &&
-	    ((test_and_clear_bit(THROTTLE_RX, &hw->usb_flags) &&
-	      !test_and_set_bit(WORK_RX_RESUME, &hw->usb_flags)) |
-	     (test_and_clear_bit(THROTTLE_TX, &hw->usb_flags) &&
-	      !test_and_set_bit(WORK_TX_RESUME, &hw->usb_flags))
-	    )) {
-		schedule_work(&hw->usb_work);
+	if (!hw->wlandev->hwremoved) {
+		bool rx_throttle = test_and_clear_bit(THROTTLE_RX, &hw->usb_flags) &&
+				   !test_and_set_bit(WORK_RX_RESUME, &hw->usb_flags);
+		bool tx_throttle = test_and_clear_bit(THROTTLE_TX, &hw->usb_flags) &&
+				   !test_and_set_bit(WORK_TX_RESUME, &hw->usb_flags);
+		/*
+		 * We need to check BOTH the RX and the TX throttle controls,
+		 * so we use the bitwise OR instead of the logical OR.
+		 */
+		if (rx_throttle | tx_throttle)
+			schedule_work(&hw->usb_work);
 	}
 
 	spin_unlock_irqrestore(&hw->ctlxq.lock, flags);

base-commit: 6ac113f741a7674e4268eea3eb13972732d83571
-- 
2.33.1.637.gf443b226ca