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Date:	Fri, 2 Jul 2010 12:22:26 +0530
From:	"Datta, Shubhrajyoti" <shubhrajyoti@...com>
To:	Jonathan Cameron <jic23@....ac.uk>
CC:	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"sfking@...dc.com" <sfking@...dc.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC] [PATCH] digital compass hmc5843



> -----Original Message-----
> From: Jonathan Cameron [mailto:jic23@....ac.uk]
> Sent: Thursday, July 01, 2010 9:29 PM
> To: Datta, Shubhrajyoti
> Cc: linux-iio@...r.kernel.org; sfking@...dc.com; linux-
> kernel@...r.kernel.org
> Subject: Re: [RFC] [PATCH] digital compass hmc5843
>
> On 07/01/10 16:12, Datta, Shubhrajyoti wrote:
> > Adding support for the Honeywell HMC5843. The interface to the device is
> i2c.
> > - Comments added
> > - The interface name of sampling frequency made similar to the
> convention
> > - The sysfs entries changed to io device
> I'm still getting spaces rather than tabs...   My guess is your email
> client is still eating tabs.
Yes not sure whats causing the issue. Will fix it.
>
> Few more coments below.  It still needs a bit blugeoning to meet the abi.
> We have to be strict or we will have nasty issues with userspace code
> finding incompatibilities between devices.
>
I completely agree will send another patch.

> Also, please document the non standard attributes under iio/Documentation
> as per the current abi docs.
Yes I take up an action item. I will do it after finalizing the code as some of the name and units I am finalizing.
>
> Thanks,
>
> Jonathan
> >
> > Signed-off-by: Shubhrajyoti D <shubhrajyoti@...com>
> > ---
> >  drivers/staging/iio/Kconfig                |    1 +
> >  drivers/staging/iio/Makefile               |    1 +
> >  drivers/staging/iio/magnetometer/Kconfig   |   15 +
> >  drivers/staging/iio/magnetometer/Makefile  |    5 +
> >  drivers/staging/iio/magnetometer/hmc5843.c |  607
> ++++++++++++++++++++++++++++
> >  5 files changed, 629 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/staging/iio/magnetometer/Kconfig
> >  create mode 100644 drivers/staging/iio/magnetometer/Makefile
> >  create mode 100644 drivers/staging/iio/magnetometer/hmc5843.c
> >
> > diff --git a/drivers/staging/iio/Kconfig b/drivers/staging/iio/Kconfig
> > index b0e6244..569b938 100644
> > --- a/drivers/staging/iio/Kconfig
> > +++ b/drivers/staging/iio/Kconfig
> > @@ -44,6 +44,7 @@ source "drivers/staging/iio/adc/Kconfig"
> >  source "drivers/staging/iio/gyro/Kconfig"
> >  source "drivers/staging/iio/imu/Kconfig"
> >  source "drivers/staging/iio/light/Kconfig"
> > +source "drivers/staging/iio/magnetometer/Kconfig"
> >
> >  source "drivers/staging/iio/trigger/Kconfig"
> >
> > diff --git a/drivers/staging/iio/Makefile b/drivers/staging/iio/Makefile
> > index 3502b39..10d1f6b 100644
> > --- a/drivers/staging/iio/Makefile
> > +++ b/drivers/staging/iio/Makefile
> > @@ -14,5 +14,6 @@ obj-y += adc/
> >  obj-y += gyro/
> >  obj-y += imu/
> >  obj-y += light/
> > +obj-y += magnetometer/
> >
> >  obj-y += trigger/
> > \ No newline at end of file
> > diff --git a/drivers/staging/iio/magnetometer/Kconfig
> b/drivers/staging/iio/magnetometer/Kconfig
> > new file mode 100644
> > index 0000000..6c67981
> > --- /dev/null
> > +++ b/drivers/staging/iio/magnetometer/Kconfig
> > @@ -0,0 +1,15 @@
> > +#
> > +# Magnetometer sensors
> > +#
> > +comment "Magnetometer sensors"
> > +
> > +config SENSORS_HMC5843
> > +       tristate "Honeywell HMC5843 3-Axis Magnetometer"
> > +       depends on I2C
> > +       help
> > +         Say Y here to add support for the Honeywell HMC 5843 3-Axis
> > +         Magnetometer (digital compass).
> > +
> > +         To compile this driver as a module, choose M here: the module
> > +         will be called hmc5843
> > +
> > diff --git a/drivers/staging/iio/magnetometer/Makefile
> b/drivers/staging/iio/magnetometer/Makefile
> > new file mode 100644
> > index 0000000..f9bfb2e
> > --- /dev/null
> > +++ b/drivers/staging/iio/magnetometer/Makefile
> > @@ -0,0 +1,5 @@
> > +#
> > +# Makefile for industrial I/O Magnetometer sensors
> > +#
> > +
> > +obj-$(CONFIG_SENSORS_HMC5843)  += hmc5843.o
> > diff --git a/drivers/staging/iio/magnetometer/hmc5843.c
> b/drivers/staging/iio/magnetometer/hmc5843.c
> > new file mode 100644
> > index 0000000..d741d39
> > --- /dev/null
> > +++ b/drivers/staging/iio/magnetometer/hmc5843.c
> > @@ -0,0 +1,607 @@
> > +/*  Copyright (c) 2010  Shubhrajyoti Datta <shubhrajyoti@...com>
> > +
> > +    This program is free software; you can redistribute it and/or
> modify
> > +    it under the terms of the GNU General Public License as published
> by
> > +    the Free Software Foundation; either version 2 of the License, or
> > +    (at your option) any later version.
> > +
> > +    This program is distributed in the hope that it will be useful,
> > +    but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +    GNU General Public License for more details.
> > +
> > +    You should have received a copy of the GNU General Public License
> > +    along with this program; if not, write to the Free Software
> > +    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> > +*/
> > +
> > +#include <linux/module.h>
> > +#include <linux/init.h>
> > +#include <linux/i2c.h>
> > +#include <linux/slab.h>
> > +#include <linux/types.h>
> > +#include "../iio.h"
> > +#include "../sysfs.h"
> > +#include "magnet.h"
> > +
> > +#define HMC5843_I2C_ADDRESS                    0x1E
> > +
> > +#define HMC5843_CONFIG_REG_A                   0x00
> > +#define HMC5843_CONFIG_REG_B                   0x01
> > +#define HMC5843_MODE_REG                       0x02
> > +#define HMC5843_DATA_OUT_X_MSB_REG             0x03
> > +#define HMC5843_DATA_OUT_X_LSB_REG             0x04
> > +#define HMC5843_DATA_OUT_Y_MSB_REG             0x05
> > +#define HMC5843_DATA_OUT_Y_LSB_REG             0x06
> > +#define HMC5843_DATA_OUT_Z_MSB_REG             0x07
> > +#define HMC5843_DATA_OUT_Z_LSB_REG             0x08
> > +#define HMC5843_STATUS_REG                     0x09
> > +#define HMC5843_ID_REG_A                       0x0A
> > +#define HMC5843_ID_REG_B                       0x0B
> > +#define HMC5843_ID_REG_C                       0x0C
> > +
> > +#define HMC5843_ID_REG_LENGTH                  0x03
> > +#define HMC5843_ID_STRING                      "H43"
> > +
> > +/*
> > + * Range settings in  (+-)Ga
> > + * */
> > +#define RANGE_GAIN_OFFSET                      0x05
> > +
> > +#define        RANGE_0_7                               0x00
> > +#define        RANGE_1_0                               0x01 /* default
> */
> > +#define        RANGE_1_5                               0x02
> > +#define        RANGE_2_0                               0x03
> > +#define        RANGE_3_2                               0x04
> > +#define        RANGE_3_8                               0x05
> > +#define        RANGE_4_5                               0x06
> > +#define        RANGE_6_5                               0x07 /* Not
> recommended */
> > +
> > +/*
> > + * Device status
> > + */
> > +#define        DATA_READY                              0x01
> > +#define        DATA_OUTPUT_LOCK                        0x02
> > +#define        VOLTAGE_REGULATOR_ENABLED               0x04
> > +
> > +/*
> > + * Mode register configuration
> > + */
> > +#define        MODE_CONVERSION_CONTINUOUS              0x00
> > +#define        MODE_CONVERSION_SINGLE                  0x01
> > +#define        MODE_IDLE                               0x02
> > +#define        MODE_SLEEP                              0x03
> > +
> > +/* Minimum Data Output Rate in 1/10 Hz  */
> > +#define RATE_OFFSET                            0x02
> > +#define RATE_BITMASK                           0x1C
> > +#define        RATE_5                                  0x00
> > +#define        RATE_10                                 0x01
> > +#define        RATE_20                                 0x02
> > +#define        RATE_50                                 0x03
> > +#define        RATE_100                                0x04
> > +#define        RATE_200                                0x05
> > +#define        RATE_500                                0x06
> > +#define        RATE_NOT_USED                           0x07
> > +
> > +/*
> > + * Device Configutration
> > + */
> > +#define        CONF_NORMAL                             0x00
> > +#define        CONF_POSITIVE_BIAS                      0x01
> > +#define        CONF_NEGATIVE_BIAS                      0x02
> > +#define        CONF_NOT_USED                           0x03
> > +#define        MEAS_CONF_MASK                          0x03
> > +
> > +static const int regval_to_counts_per_mg[] = {
> > +       1620,
> > +       1300,
> > +       970,
> > +       780,
> > +       530,
> > +       460,
> > +       390,
> > +       280
> > +};
> > +static const int regval_to_input_field_mg[] = {
> > +       700,
> > +       1000,
> > +       1500,
> > +       2000,
> > +       3200,
> > +       3800,
> > +       4500,
> > +       6500
> > +};
> > +static const int samp_freq_to_regval[] = {
> > +       5,
> > +       10,
> > +       20,
> > +       50,
> > +       100,
> > +       200,
> > +       500,
> > +};
> > +
> > +/* Addresses to scan: 0x1E */
> > +static const unsigned short normal_i2c[] = { HMC5843_I2C_ADDRESS,
> > +                                                       I2C_CLIENT_END
> };
> > +
> > +/* Each client has this additional data */
> > +struct hmc5843_data {
> > +       struct iio_dev  *indio_dev;
> > +       u8              rate;
> > +       u8              meas_conf;
> > +       u8              operating_mode;
> > +       u8              range;
> > +};
> > +
> This is not needed.  init_client is only called after it is defined.
> > +static void hmc5843_init_client(struct i2c_client *client);
> > +
> > +static s32 hmc5843_configure(struct i2c_client *client,
> > +                                      u8 operating_mode)
> > +{
> > +       /* The lower two bits contain the current conversion mode */
> > +       return i2c_smbus_write_byte_data(client,
> > +                                       HMC5843_MODE_REG,
> > +                                       (operating_mode & 0x03));
> > +}
> > +
> > +/* Return the measurement value from the  specified channel */
> > +
> Nitpick: bonus blank line.  Have the comment immediately above
> the function it referring to...
> > +static ssize_t hmc5843_read_measurement(struct device *dev,
> > +               struct device_attribute *attr,
> > +               char *buf)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       s16 coordinate_val;
> > +       struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> > +       s32 result;
> > +
> > +       result = i2c_smbus_read_byte_data(client, HMC5843_STATUS_REG);
> > +       while (!(result & DATA_READY))
> > +               result = i2c_smbus_read_byte_data(client,
> HMC5843_STATUS_REG);
> > +
> > +       result = i2c_smbus_read_word_data(client, this_attr->address);
> > +       if (result < 0)
> > +               return -EINVAL;
> > +
> > +       coordinate_val  = (s16)swab16((u16)result);
> > +       return sprintf(buf, "%d\n", coordinate_val);
> > +}
> > +static IIO_DEV_ATTR_MAGN_X(hmc5843_read_measurement,
> > +               HMC5843_DATA_OUT_X_MSB_REG);
> > +static IIO_DEV_ATTR_MAGN_Y(hmc5843_read_measurement,
> > +               HMC5843_DATA_OUT_Y_MSB_REG);
> > +static IIO_DEV_ATTR_MAGN_Z(hmc5843_read_measurement,
> > +               HMC5843_DATA_OUT_Z_MSB_REG);
> Good to see the docs.  If possible can you do a file for
> staging/iio/Documentation
> so these are available to people without having to dive in the source
> code.
> I would imaging this functionality is going to interact strangely with
> the read attributes seeing as I assume they will fail if the device
> is asleep?
> > +/*
> > + * From the datasheet
> > + * 0 - Continuous-Conversion Mode: In continuous-conversion mode, the
> > + * device continuously performs conversions an places the result in the
> > + * data register.
> > + *
> > + * 1 - Single-Conversion Mode : device performs a single measurement,
> > + *  sets RDY high and returned to sleep mode
> > + *
> > + * 2 - Idle Mode :  Device is placed in idle mode.
> > + *
> > + * 3 - Sleep Mode. Device is placed in sleep mode.
> > + *
> > + */
> > +static ssize_t hmc5843_show_operating_mode(struct device *dev,
> > +                                       struct device_attribute *attr,
> > +                                       char *buf)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       return sprintf(buf, "%d\n", data->operating_mode);
> > +}
> New line please.
> > +static ssize_t hmc5843_set_operating_mode(struct device *dev,
> > +                               struct device_attribute *attr,
> > +                               const char *buf,
> > +                               size_t count)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> > +       unsigned long operating_mode = 0;
> > +       s32 status;
> > +       int error;
> > +       error = strict_strtoul(buf, 10, &operating_mode);
> > +       if (error)
> > +               return error;
> > +       dev_dbg(dev, "set Conversion mode to %lu\n", operating_mode);
> > +       if (operating_mode > MODE_SLEEP)
> > +                       return -EINVAL;
> > +
> > +       status = i2c_smbus_write_byte_data(client, this_attr->address,
> > +                                       operating_mode);
> > +       if (status)
> > +               return -EINVAL;
> > +
> > +       data->operating_mode = operating_mode;
> > +       return count;
> > +}
> > +static IIO_DEVICE_ATTR(operating_mode,
> > +                       S_IWUSR | S_IRUGO,
> > +                       hmc5843_show_operating_mode,
> > +                       hmc5843_set_operating_mode,
> > +                       HMC5843_MODE_REG);
> new line please
> > +/*
> > + * API for setting the measurement configuration to
> > + * Normal, Positive bias and Negitive bias
> > + * From the datasheet
> > + *
> > + * Normal measurement configuration (default): In normal measurement
> > + * configuration the device follows normal measurement flow. Pins BP
> and BN
> > + * are left floating and high impedance.
> > + *
> > + * Positive bias configuration: In positive bias configuration, a
> positive
> > + * current is forced across the resistive load on pins BP and BN.
> > + *
> > + * Negative bias configuration. In negative bias configuration, a
> negative
> > + * current is forced across the resistive load on pins BP and BN.
> > + *
> > + */
> Ah, so the resulting change in the device is dependent on what BP and BN
> are wired up to.  Thanks for the clarification.  Again, if this can go
> in a seperate documentation file that would be great.
> > +static s32 hmc5843_set_meas_conf(struct i2c_client *client,
> > +                                     u8 meas_conf)
> > +{
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       u8 reg_val;
> > +       reg_val = (meas_conf & MEAS_CONF_MASK) |  (data->rate <<
> RATE_OFFSET);
> > +       return i2c_smbus_write_byte_data(client, HMC5843_CONFIG_REG_A,
> reg_val);
> > +}
> > +
> > +static ssize_t hmc5843_show_measurement_configuration(struct device
> *dev,
> > +                                               struct device_attribute
> *attr,
> > +                                               char *buf)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       return sprintf(buf, "%d\n", data->meas_conf);
> > +}
> > +
> > +static ssize_t hmc5843_set_measurement_configuration(struct device
> *dev,
> > +                                               struct device_attribute
> *attr,
> > +                                               const char *buf,
> > +                                               size_t count)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       unsigned long meas_conf = 0;
> > +
> > +       int error = strict_strtoul(buf, 10, &meas_conf);
> > +       if (error)
> > +               return error;
> > +       dev_dbg(dev, "set mode to %lu\n", meas_conf);
> > +       if (hmc5843_set_meas_conf(client, meas_conf))
> > +               return -EINVAL;
> > +       data->meas_conf = meas_conf;
> > +       return count;
> > +}
> > +static IIO_DEVICE_ATTR(meas_conf,
> > +                       S_IWUSR | S_IRUGO,
> > +                       hmc5843_show_measurement_configuration,
> > +                       hmc5843_set_measurement_configuration,
> > +                       0);
> New line
> > +/*
> > + * From Datasheet
> > + * The table shows the minimum data output
> > + * Value       | Minimum data output rate(Hz)
> > + * 0           | 0.5
> > + * 1           | 1
> > + * 2           | 2
> > + * 3           | 5
> > + * 4           | 10 (default)
> > + * 5           | 20
> > + * 6           | 50
> > + * 7           | Not used
> > + */
> Thanks for chaning this, but the abi does specifiy units....
> > +static ssize_t show_avail_samp_freq(struct device *dev,
> > +                       struct device_attribute *attr, char *buf)
> > +{
> > +       char freq[] = {"5 , 10, 20, 50, 100, 200 ,500"};
> > +       return sprintf(buf, "In units of 1/10 hz: %s\n", freq);
> Gah.  This has to be machine readable or no userspace program
> is ever going to be able to use it.  So a simple list. The abi
> specifies the units (Hz).
> > +}
> The IIO_CONST_ATTR macro makes this easy. There is even a convenient
> macro for this case.
>
> static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("0.5 1 2 5 10 20 50");
>
>
> Then strncmp with the options to set the value up.  The rounding approach
> gets tricky with a non integer value so probably easier to only allow
> these
> values.
>
> > +static IIO_DEV_ATTR_AVAIL_SAMP_FREQ(show_avail_samp_freq);
> > +
> > +static s32 hmc5843_set_rate(struct i2c_client *client,
> > +                               u8 rate)
> > +{
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       u8 reg_val;
> > +
> > +       reg_val = (data->meas_conf) |  (rate << RATE_OFFSET);
> > +       if (rate >= RATE_NOT_USED) {
> > +               dev_err(&client->dev,
> > +                       "This data output rate is not supported \n");
> > +               return -EINVAL;
> > +       }
> > +       return i2c_smbus_write_byte_data(client, HMC5843_CONFIG_REG_A,
> reg_val);
> > +}
> > +
> > +static ssize_t set_sampling_frequency(struct device *dev,
> > +                                       struct device_attribute *attr,
> > +                                       const char *buf, size_t count)
> > +{
> > +
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       unsigned long rate = 0;
> > +       unsigned long reg_val;
> > +       int error;
> > +
> > +       error = strict_strtoul(buf, 10, &rate);
> > +       if (error)
> > +               return error;
> > +       if (rate < 10)
> > +               reg_val = RATE_5;
> > +       else if (rate < 20)
> > +               reg_val = RATE_10;
> > +       else if (rate < 50)
> > +               reg_val = RATE_20;
> > +       else if (rate < 100)
> > +               reg_val = RATE_50;
> > +       else if (rate < 200)
> > +               reg_val = RATE_100;
> > +       else if (rate < 500)
> > +               reg_val = RATE_200;
> > +       else
> > +               reg_val = RATE_500;
> > +
> > +       dev_dbg(dev, "set rate to %lu\n", reg_val);
> > +       if (hmc5843_set_rate(client, reg_val) == -EINVAL)
> > +               return -EINVAL;
> > +       data->rate = rate;
> > +       return count;
> > +}
> > +
> > +static ssize_t show_sampling_frequency(struct device *dev,
> > +                       struct device_attribute *attr, char *buf)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> > +       u32 rate;
> > +
> > +       rate = i2c_smbus_read_byte_data(client,  this_attr->address);
> > +       if (rate < 0)
> > +               return -EINVAL;
> > +       rate = (rate & RATE_BITMASK) >> RATE_OFFSET;
> This also becomes a query into a string array to allow that 0.5 value.
> > +       return sprintf(buf, "%d\n", samp_freq_to_regval[rate]);
> > +}
> > +static IIO_DEVICE_ATTR(sampling_frequency,
> > +                       S_IWUSR | S_IRUGO,
> > +                       show_sampling_frequency,
> > +                       set_sampling_frequency,
> > +                       HMC5843_CONFIG_REG_A);
>
> It isn't always helpful to just have documentation like this in the
> kernel code. Please add an abi description to staging/iio/Documentation/
>
> Also, if at all possible, can get this to conform to equivalent of
> in0_scale (see the sysfs-class-iio file). Abi says that magn parameters
> are to be converted to Gauss (maybe we should make that milli-gauss?)
>
> Thus we need an additional attribute saying what is available.
>
> static IIO_CONST_ATTR(magn_scale_available, "0.000000617284 0.00000076923
> <others> 0.00000357143");
> The numbers correspond to A where value_in_gauss=A*raw_reading + B/
>
> We then match against these exact values (or go for nearest) on the
> gain_store
> and output the relevant value on gain_show.
>
> Although these values correspond directly to table 12 in the datasheet,
> I'm
> a little confused by this table. Perhaps you can clarify?
>
> Take the top line, Maximum value is 2047 counts.  So if we have 1620
> counts/ milli gauss
> then this equals a couple of milli gauss not 0.7 gauss?
> > +/*
> > + * From Datasheet
> > + *     Nominal gain settings
> > + * Value       | Sensor Input Field Range(Ga)  | Gain(counts/ milli-
> gauss)
> > + *0            |(+-)0.7                        |1620
> > + *1            |(+-)1.0                        |1300
> > + *2            |(+-)1.5                        |970
> > + *3            |(+-)2.0                        |780
> > + *4            |(+-)3.2                        |530
> > + *5            |(+-)3.8                        |460
> > + *6            |(+-)4.5                        |390
> > + *7            |(+-)6.5                        |280
> > + */
> > +static ssize_t show_range(struct device *dev,
> > +                               struct device_attribute *attr,
> > +                               char *buf)
> > +{
> > +       u8 range;
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +
> > +       range = data->range;
> No units please.  That just makes things tricky for userspace whilst
> giving no
> additional information as the ABI specifies the allowed units.  You also
> encourage
> people to apply units to the values they write to these attributes.
> > +       return sprintf(buf, " %dmGa\n",
> regval_to_input_field_mg[range]);
> > +}
> > +
> > +static ssize_t set_range(struct device *dev,
> > +                       struct device_attribute *attr,
> > +                       const char *buf,
> > +                       size_t count)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       unsigned long range = 0;
> > +       int error;
> > +
> > +       error = strict_strtoul(buf, 10, &range);
> > +       if (error)
> > +               return error;
> > +       dev_dbg(dev, "set range to %lu\n", range);
> > +
> > +       if (range > RANGE_6_5)
> > +               return -EINVAL;
> > +
> > +       data->range = range;
> > +       range = range << RANGE_GAIN_OFFSET;
> > +       if (i2c_smbus_write_byte_data(client, this_attr->address, range)
> ==
> > +
> -EINVAL)
> > +               return -EINVAL;
> > +
> > +       return count;
> > +}
> > +
> > +static IIO_DEVICE_ATTR(magn_range,
> > +                       S_IWUSR | S_IRUGO,
> > +                       show_range,
> > +                       set_range,
> > +                       HMC5843_CONFIG_REG_B);
> > +
> > +static ssize_t show_gain(struct device *dev,
> > +                       struct device_attribute *attr,
> > +                       char *buf)
> > +{
> > +       struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > +       struct i2c_client *client = to_i2c_client(indio_dev-
> >dev.parent);
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       return sprintf(buf, "%d\n", regval_to_counts_per_mg[data-
> >range]);
> > +}
> > +static IIO_DEVICE_ATTR(magn_gain, S_IRUGO, show_gain, NULL , 0);
> > +
> > +
> > +static struct attribute *hmc5843_attributes[] = {
> > +       &iio_dev_attr_meas_conf.dev_attr.attr,
> > +       &iio_dev_attr_operating_mode.dev_attr.attr,
> > +       &iio_dev_attr_sampling_frequency.dev_attr.attr,
> > +       &iio_dev_attr_magn_range.dev_attr.attr,
> > +       &iio_dev_attr_magn_gain.dev_attr.attr,
> > +       &iio_dev_attr_magn_x_raw.dev_attr.attr,
> > +       &iio_dev_attr_magn_y_raw.dev_attr.attr,
> > +       &iio_dev_attr_magn_z_raw.dev_attr.attr,
> > +       &iio_dev_attr_available_sampling_frequency.dev_attr.attr,
> > +       NULL
> > +};
> > +
> > +static const struct attribute_group hmc5843_group = {
> > +       .attrs = hmc5843_attributes,
> > +};
> > +
> > +static int hmc5843_detect(struct i2c_client *client,
> > +                         struct i2c_board_info *info)
> > +{
> > +       unsigned char id_str[HMC5843_ID_REG_LENGTH];
> > +
> > +       if (client->addr != HMC5843_I2C_ADDRESS)
> > +               return -ENODEV;
> > +
> > +       if (i2c_smbus_read_i2c_block_data(client, HMC5843_ID_REG_A,
> > +                               HMC5843_ID_REG_LENGTH, id_str)
> > +                       != HMC5843_ID_REG_LENGTH)
> > +               return -ENODEV;
> > +
> > +       if (0 != strncmp(id_str, HMC5843_ID_STRING,
> HMC5843_ID_REG_LENGTH))
> > +               return -ENODEV;
> > +
> > +       return 0;
> > +}
> > +
> > +/* Called when we have found a new HMC5843. */
> > +static void hmc5843_init_client(struct i2c_client *client)
> > +{
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       hmc5843_set_meas_conf(client, data->meas_conf);
> > +       hmc5843_set_rate(client, data->rate);
> > +       hmc5843_configure(client, data->operating_mode);
> > +       i2c_smbus_write_byte_data(client, HMC5843_CONFIG_REG_B, data-
> >range);
> > +       pr_info("HMC5843 initialized\n");
> > +}
> > +
> > +static int hmc5843_probe(struct i2c_client *client,
> > +                        const struct i2c_device_id *id)
> > +{
> > +       struct hmc5843_data *data;
> > +       int err = 0;
> > +
> > +       data = kzalloc(sizeof(struct hmc5843_data), GFP_KERNEL);
> > +       if (!data) {
> > +               err = -ENOMEM;
> > +               goto exit;
> > +       }
> > +
> > +       /* default settings at probe */
> > +
> > +       data->meas_conf = CONF_NORMAL;
> > +       data->range = RANGE_1_0;
> > +       data->operating_mode = MODE_CONVERSION_CONTINUOUS;
> > +
> > +       i2c_set_clientdata(client, data);
> > +
> > +       /* Initialize the HMC5843 chip */
> > +       hmc5843_init_client(client);
> > +
> > +       data->indio_dev = iio_allocate_device();
> > +       if (!data->indio_dev) {
> > +               err = -ENOMEM;
> > +               goto exit_free;
> > +       }
> > +       data->indio_dev->attrs = &hmc5843_group;
> > +       data->indio_dev->dev.parent = &client->dev;
> > +       data->indio_dev->dev_data = (void *)(data);
> > +       data->indio_dev->driver_module = THIS_MODULE;
> > +       data->indio_dev->modes = INDIO_DIRECT_MODE;
> > +       err = iio_device_register(data->indio_dev);
> > +       if (err)
> > +               goto exit_free;
> > +       return 0;
> > +exit_free:
> > +       kfree(data);
> > +exit:
> > +       return err;
> > +}
> > +
> > +static int hmc5843_remove(struct i2c_client *client)
> > +{
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +        /*  sleep mode to save power */
> > +       hmc5843_configure(client, MODE_SLEEP);
> > +       iio_device_unregister(data->indio_dev);
> > +       sysfs_remove_group(&client->dev.kobj, &hmc5843_group);
> > +       kfree(i2c_get_clientdata(client));
> > +       return 0;
> > +}
> > +
> > +static int hmc5843_suspend(struct i2c_client *client, pm_message_t
> mesg)
> > +{
> > +       hmc5843_configure(client, MODE_SLEEP);
> > +       return 0;
> > +}
> > +
> > +static int hmc5843_resume(struct i2c_client *client)
> > +{
> > +       struct hmc5843_data *data = i2c_get_clientdata(client);
> > +       hmc5843_configure(client, data->operating_mode);
> > +       return 0;
> > +}
> > +
> > +static const struct i2c_device_id hmc5843_id[] = {
> > +       { "hmc5843", 0 },
> > +       { }
> > +};
> > +
> > +static struct i2c_driver hmc5843_driver = {
> > +       .driver = {
> > +               .name   = "hmc5843",
> > +       },
> > +       .id_table       = hmc5843_id,
> > +       .probe          = hmc5843_probe,
> > +       .remove         = hmc5843_remove,
> > +       .detect         = hmc5843_detect,
> > +       .address_list   = normal_i2c,
> > +       .suspend        = hmc5843_suspend,
> > +       .resume         = hmc5843_resume,
> > +};
> > +
> > +static int __init hmc5843_init(void)
> > +{
> You still need to remove this pair of printks.
> > +       printk(KERN_INFO "init!\n");
> > +       return i2c_add_driver(&hmc5843_driver);
> > +}
> > +
> > +static void __exit hmc5843_exit(void)
> > +{
> > +       printk(KERN_INFO "exit!\n");
> > +       i2c_del_driver(&hmc5843_driver);
> > +}
> > +
> > +MODULE_AUTHOR("Shubhrajyoti Datta <shubhrajyoti@...com");
> > +MODULE_DESCRIPTION("HMC5843 driver");
> > +MODULE_LICENSE("GPL");
> > +
> > +module_init(hmc5843_init);
> > +module_exit(hmc5843_exit);
> > --
> > 1.5.4.7
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >

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