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[82.64.73.52]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438904087cbsm41520955e9.3.2025.01.17.09.55.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jan 2025 09:55:02 -0800 (PST) Date: Fri, 17 Jan 2025 18:55:00 +0100 From: Dave Penkler To: David Laight Cc: gregkh@linuxfoundation.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] staging: gpib: Fix inadvertent negative shift Message-ID: References: <20250116110014.15577-1-dpenkler@gmail.com> <20250116224003.28675481@pumpkin> Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250116224003.28675481@pumpkin> On Thu, Jan 16, 2025 at 10:40:03PM +0000, David Laight wrote: > On Thu, 16 Jan 2025 12:00:14 +0100 > Dave Penkler wrote: > > > During the initial checkpatch cleanup, when removing blanks > > after open parentheses, a minus sign in the argument of a shift > > operation was deleted by mistake. This transformed a pre-decrement > > operation into a negation. > > > > The result of a negative shift is undefined and a warning was > > signalled by sparse. > > > > Restore the pre-decrement operation. > > > > Fixes: 6c52d5e3cde2 ("staging: gpib: Add common include files for GPIB drivers") > > Signed-off-by: Dave Penkler > > --- > > drivers/staging/gpib/include/amcc5920.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/gpib/include/amcc5920.h b/drivers/staging/gpib/include/amcc5920.h > > index 766b3799223f..7a88bd282feb 100644 > > --- a/drivers/staging/gpib/include/amcc5920.h > > +++ b/drivers/staging/gpib/include/amcc5920.h > > @@ -22,7 +22,7 @@ static const int bits_per_region = 8; > > > > static inline uint32_t amcc_wait_state_bits(unsigned int region, unsigned int num_wait_states) > > { > > - return (num_wait_states & 0x7) << (-region * bits_per_region); > > + return (num_wait_states & 0x7) << (--region * bits_per_region); > > It would be much better to use (region - 1). Hi, You are right. I will send a separate patch to change this instance and all the others in the file. cheers, -dave