From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Cameron Subject: Re: [PATCH 07/11] iio/adc: (max1363) Fix data conversion problems Date: Sat, 02 Feb 2013 10:08:48 +0000 Message-ID: <510CE5B0.3050207@kernel.org> References: <1359668588-13678-1-git-send-email-linux@roeck-us.net> <1359668588-13678-8-git-send-email-linux@roeck-us.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1359668588-13678-8-git-send-email-linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org> Sender: linux-iio-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Guenter Roeck Cc: linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Naveen Krishna Chatradhi , Lars-Peter Clausen , Doug Anderson , Tomasz Figa , Grant Likely , Rob Herring List-Id: devicetree@vger.kernel.org On 01/31/2013 09:43 PM, Guenter Roeck wrote: > For chips with more than 8 bit ADC resolution, received data was always > masked against 0xfff, ie with a 12 bit mask. This can result in bad data > for chips with 10 bit resolution if those chips have higher bits set > (seen with MAX1139). > > The receive buffer was defined as char array. This could result in > unintentional sign extensions if the upper bit in a received byte > was set. Since the chip is configured for unipolar mode, we never > have to handle negative values, and sign extensions are never needed. > > Signed-off-by: Guenter Roeck Applied to togreg branch of iio.git > --- > drivers/iio/adc/max1363.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c > index 2c773b4..fdc8be9 100644 > --- a/drivers/iio/adc/max1363.c > +++ b/drivers/iio/adc/max1363.c > @@ -334,7 +334,7 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev, > { > int ret = 0; > s32 data; > - char rxbuf[2]; > + u8 rxbuf[2]; > struct max1363_state *st = iio_priv(indio_dev); > struct i2c_client *client = st->client; > > @@ -366,7 +366,8 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev, > ret = data; > goto error_ret; > } > - data = (s32)(rxbuf[1]) | ((s32)(rxbuf[0] & 0x0F)) << 8; > + data = (rxbuf[1] | rxbuf[0] << 8) & > + ((1 << st->chip_info->bits) - 1); > } else { > /* Get reading */ > data = i2c_master_recv(client, rxbuf, 1); >