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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38bf3221baasm936184f8f.35.2025.01.16.14.40.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jan 2025 14:40:04 -0800 (PST) Date: Thu, 16 Jan 2025 22:40:03 +0000 From: David Laight To: Dave Penkler 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: <20250116224003.28675481@pumpkin> In-Reply-To: <20250116110014.15577-1-dpenkler@gmail.com> References: <20250116110014.15577-1-dpenkler@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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). David > }; > > enum amcc_prefetch_bits {