linux-kernel - [PATCH 4.9 048/101] x86/olpc: fix logical not is only applied to the left hand side

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Message-Id: <20220823080036.369144154@linuxfoundation.org>
Date:   Tue, 23 Aug 2022 10:03:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        kernel test robot <lkp@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Yury Norov <yury.norov@...il.com>
Subject: [PATCH 4.9 048/101] x86/olpc: fix logical not is only applied to the left hand side

From: Alexander Lobakin <alexandr.lobakin@...el.com>

commit 3a2ba42cbd0b669ce3837ba400905f93dd06c79f upstream.

The bitops compile-time optimization series revealed one more
problem in olpc-xo1-sci.c:send_ebook_state(), resulted in GCC
warnings:

arch/x86/platform/olpc/olpc-xo1-sci.c: In function 'send_ebook_state':
arch/x86/platform/olpc/olpc-xo1-sci.c:83:63: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
   83 |         if (!!test_bit(SW_TABLET_MODE, ebook_switch_idev->sw) == state)
      |                                                               ^~
arch/x86/platform/olpc/olpc-xo1-sci.c:83:13: note: add parentheses around left hand side expression to silence this warning

Despite this code working as intended, this redundant double
negation of boolean value, together with comparing to `char`
with no explicit conversion to bool, makes compilers think
the author made some unintentional logical mistakes here.
Make it the other way around and negate the char instead
to silence the warnings.

Fixes: d2aa37411b8e ("x86/olpc/xo1/sci: Produce wakeup events for buttons and switches")
Cc: stable@...r.kernel.org # 3.5+
Reported-by: Guenter Roeck <linux@...ck-us.net>
Reported-by: kernel test robot <lkp@...el.com>
Reviewed-and-tested-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
Signed-off-by: Yury Norov <yury.norov@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/platform/olpc/olpc-xo1-sci.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/platform/olpc/olpc-xo1-sci.c
+++ b/arch/x86/platform/olpc/olpc-xo1-sci.c
@@ -85,7 +85,7 @@ static void send_ebook_state(void)
 		return;
 	}
 
-	if (!!test_bit(SW_TABLET_MODE, ebook_switch_idev->sw) == state)
+	if (test_bit(SW_TABLET_MODE, ebook_switch_idev->sw) == !!state)
 		return; /* Nothing new to report. */
 
 	input_report_switch(ebook_switch_idev, SW_TABLET_MODE, state);