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Mon, 18 Nov 2019 00:09:41 -0800 (PST) Date: Mon, 18 Nov 2019 00:09:39 -0800 From: Dmitry Torokhov To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Wolfram Sang , linux-iio@vger.kernel.org, Luca Ceresoli , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/3] i2c: smbus: switch from loops to memcpy Message-ID: <20191118080939.GC251795@dtor-ws> References: <20191112203132.163306-1-dmitry.torokhov@gmail.com> <20191112203132.163306-4-dmitry.torokhov@gmail.com> <20191118074757.edyfvz5s3pqnu67y@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20191118074757.edyfvz5s3pqnu67y@pengutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 18, 2019 at 08:47:57AM +0100, Uwe Kleine-König wrote: > Hello Dmitry, > > On Tue, Nov 12, 2019 at 12:31:32PM -0800, Dmitry Torokhov wrote: > > When copying memory from one buffer to another, instead of open-coding > > loops with byte-by-byte copies let's use memcpy() which might be a bit > > faster and makes intent more clear. > > > > Signed-off-by: Dmitry Torokhov > > > > --- > > > > Changes in v3: > > - new patch using memcpy() for moving data around > > > > drivers/i2c/i2c-core-smbus.c | 15 +++++---------- > > 1 file changed, 5 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c > > index 7b4e2270eeda1..bbafdd3b1b114 100644 > > --- a/drivers/i2c/i2c-core-smbus.c > > +++ b/drivers/i2c/i2c-core-smbus.c > > @@ -397,8 +397,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, > > } > > > > i2c_smbus_try_get_dmabuf(&msg[0], command); > > - for (i = 1; i < msg[0].len; i++) > > - msg[0].buf[i] = data->block[i - 1]; > > + memcpy(msg[0].buf + 1, data->block, msg[0].len - 1); > > Can it happen that msg[0].len is zero? No, it can not, because of the "msg[0].len = data->block[0] + 2;" line above. Thanks. -- Dmitry