linux/drivers/iio/pressure/mpl115.c
Peter Rosin 6a6e1d56a0 iio: pressure: mpl115: do not rely on structure field ordering
Fixes a regression triggered by a change in the layout of
struct iio_chan_spec, but the real bug is in the driver which assumed
a specific structure layout in the first place. Hint: the three bits were
not OR:ed together as implied by the indentation prior to this patch,
there was a comma between the first two, which accidentally moved the
..._SCALE and ..._OFFSET bits to the next structure field. That field
was .info_mask_shared_by_type before the _available attributes was added
by commit 5123960007 ("iio:core: add a callback to allow drivers to
provide _available attributes") and .info_mask_separate_available
afterwards, and the regression happened.

info_mask_shared_by_type is actually a better choice than the originally
intended info_mask_separate for the ..._SCALE and ..._OFFSET bits since
a constant is returned from mpl115_read_raw for the scale/offset. Using
info_mask_shared_by_type also preserves the behavior from before the
regression and is therefore less likely to cause other interesting side
effects.

The above mentioned regression causes unintended sysfs attibutes to
show up that are not backed by code, in turn causing a NULL pointer
defererence to happen on access.

Fixes: 3017d90e89 ("iio: Add Freescale MPL115A2 pressure / temperature sensor driver")
Fixes: 5123960007 ("iio:core: add a callback to allow drivers to provide _available attributes")
Signed-off-by: Peter Rosin <peda@axentia.se>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
2017-02-11 09:00:44 +00:00

201 lines
4.5 KiB
C

/*
* mpl115.c - Support for Freescale MPL115A pressure/temperature sensor
*
* Copyright (c) 2014 Peter Meerwald <pmeerw@pmeerw.net>
*
* This file is subject to the terms and conditions of version 2 of
* the GNU General Public License. See the file COPYING in the main
* directory of this archive for more details.
*
* TODO: shutdown pin
*
*/
#include <linux/module.h>
#include <linux/iio/iio.h>
#include <linux/delay.h>
#include "mpl115.h"
#define MPL115_PADC 0x00 /* pressure ADC output value, MSB first, 10 bit */
#define MPL115_TADC 0x02 /* temperature ADC output value, MSB first, 10 bit */
#define MPL115_A0 0x04 /* 12 bit integer, 3 bit fraction */
#define MPL115_B1 0x06 /* 2 bit integer, 13 bit fraction */
#define MPL115_B2 0x08 /* 1 bit integer, 14 bit fraction */
#define MPL115_C12 0x0a /* 0 bit integer, 13 bit fraction */
#define MPL115_CONVERT 0x12 /* convert temperature and pressure */
struct mpl115_data {
struct device *dev;
struct mutex lock;
s16 a0;
s16 b1, b2;
s16 c12;
const struct mpl115_ops *ops;
};
static int mpl115_request(struct mpl115_data *data)
{
int ret = data->ops->write(data->dev, MPL115_CONVERT, 0);
if (ret < 0)
return ret;
usleep_range(3000, 4000);
return 0;
}
static int mpl115_comp_pressure(struct mpl115_data *data, int *val, int *val2)
{
int ret;
u16 padc, tadc;
int a1, y1, pcomp;
unsigned kpa;
mutex_lock(&data->lock);
ret = mpl115_request(data);
if (ret < 0)
goto done;
ret = data->ops->read(data->dev, MPL115_PADC);
if (ret < 0)
goto done;
padc = ret >> 6;
ret = data->ops->read(data->dev, MPL115_TADC);
if (ret < 0)
goto done;
tadc = ret >> 6;
/* see Freescale AN3785 */
a1 = data->b1 + ((data->c12 * tadc) >> 11);
y1 = (data->a0 << 10) + a1 * padc;
/* compensated pressure with 4 fractional bits */
pcomp = (y1 + ((data->b2 * (int) tadc) >> 1)) >> 9;
kpa = pcomp * (115 - 50) / 1023 + (50 << 4);
*val = kpa >> 4;
*val2 = (kpa & 15) * (1000000 >> 4);
done:
mutex_unlock(&data->lock);
return ret;
}
static int mpl115_read_temp(struct mpl115_data *data)
{
int ret;
mutex_lock(&data->lock);
ret = mpl115_request(data);
if (ret < 0)
goto done;
ret = data->ops->read(data->dev, MPL115_TADC);
done:
mutex_unlock(&data->lock);
return ret;
}
static int mpl115_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
struct mpl115_data *data = iio_priv(indio_dev);
int ret;
switch (mask) {
case IIO_CHAN_INFO_PROCESSED:
ret = mpl115_comp_pressure(data, val, val2);
if (ret < 0)
return ret;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CHAN_INFO_RAW:
/* temperature -5.35 C / LSB, 472 LSB is 25 C */
ret = mpl115_read_temp(data);
if (ret < 0)
return ret;
*val = ret >> 6;
return IIO_VAL_INT;
case IIO_CHAN_INFO_OFFSET:
*val = -605;
*val2 = 750000;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CHAN_INFO_SCALE:
*val = -186;
*val2 = 915888;
return IIO_VAL_INT_PLUS_MICRO;
}
return -EINVAL;
}
static const struct iio_chan_spec mpl115_channels[] = {
{
.type = IIO_PRESSURE,
.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
},
{
.type = IIO_TEMP,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
.info_mask_shared_by_type =
BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE),
},
};
static const struct iio_info mpl115_info = {
.read_raw = &mpl115_read_raw,
.driver_module = THIS_MODULE,
};
int mpl115_probe(struct device *dev, const char *name,
const struct mpl115_ops *ops)
{
struct mpl115_data *data;
struct iio_dev *indio_dev;
int ret;
indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
data = iio_priv(indio_dev);
data->dev = dev;
data->ops = ops;
mutex_init(&data->lock);
indio_dev->info = &mpl115_info;
indio_dev->name = name;
indio_dev->dev.parent = dev;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->channels = mpl115_channels;
indio_dev->num_channels = ARRAY_SIZE(mpl115_channels);
ret = data->ops->init(data->dev);
if (ret)
return ret;
ret = data->ops->read(data->dev, MPL115_A0);
if (ret < 0)
return ret;
data->a0 = ret;
ret = data->ops->read(data->dev, MPL115_B1);
if (ret < 0)
return ret;
data->b1 = ret;
ret = data->ops->read(data->dev, MPL115_B2);
if (ret < 0)
return ret;
data->b2 = ret;
ret = data->ops->read(data->dev, MPL115_C12);
if (ret < 0)
return ret;
data->c12 = ret;
return devm_iio_device_register(dev, indio_dev);
}
EXPORT_SYMBOL_GPL(mpl115_probe);
MODULE_AUTHOR("Peter Meerwald <pmeerw@pmeerw.net>");
MODULE_DESCRIPTION("Freescale MPL115 pressure/temperature driver");
MODULE_LICENSE("GPL");