Date:	Wed, 01 Jul 2009 19:10:35 +0000
From:	Jonathan Cameron <jic23@....ac.uk>
To:	Chris Verges <chrisv@...erswitching.com>
CC:	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org
Subject: Re: [lm-sensors] [PATCH] adxl345 accelerometer hwmon driver


> Hi kernel hackers,
> 
> Here is a patch that adds support to the Linux kernel for Analog
> Device's ADXL345 chip.  It is an accelerometer that uses I2C and HWMON.
> When I looked into the MAINTAINERS file for the appropriate list, the
> "Orphan" status of "Hardware Monitoring" confused me as to the proper
> list for this patch ... please let me know if I need to forward it
> elsewhere.
Hi Chris,

Just for reference this chip is definitely on my list of ones to support
via the Industrial I/O (iio) framework, I just haven't managed to get hold
of one as yet!  It's particualrly interesting to me because of the fifo
buffering functionality as currently I only have access to a VTI chip
that does something similar.

A new version of the IIO framework will get posted just
as soon as I've had a few mins to bring the documentation / demo userspace
apps up to date with the current code state.
I've been chasing down bugs for the last week.

First big question is:

What are you actually doing with it?  If you aren't doing hardware
monitoring then I would expect you aren't going to receive a favourable
response on here. (see the original IIO discussion on LKML for why I
started writing that in the first place.
http://lkml.org/lkml/2008/5/20/135)
It's somewhat out of date and incomplete, but there is a white paper draft at
http://www-sigproc.eng.cam.ac.uk/~jic23/iio.pdf

I'll take a look at the actual code tomorrow.  Always good to see another
accelerometer driver.

Thanks,

Jonathan

> 
> ALPHA Warning: THIS CODE COMPILES WITHOUT ERROR, BUT HAS NOT BEEN TESTED
> YET.
> 
> I'd appreciate feedback from those who have the time/interest to help!
> Code review would be great, someone with hardware for testing would be
> excellent.
> 
> Thanks,
> Chris
> 
> 
> --- PATCH BELOW ---
> 
> Signed-off-by: Chris Verges <chrisv@...erswitching.com>
> Index: drivers/hwmon/Makefile
> ===================================================================
> --- linux-2.6.29.3-orig/drivers/hwmon/Makefile	(revision 33)
> +++ linux-2.6.29.3/drivers/hwmon/Makefile	(revision 49)
> @@ -29,6 +29,7 @@
>  obj-$(CONFIG_SENSORS_ADT7470)	+= adt7470.o
>  obj-$(CONFIG_SENSORS_ADT7473)	+= adt7473.o
>  obj-$(CONFIG_SENSORS_ADT7475)	+= adt7475.o
> +obj-$(CONFIG_SENSORS_ADXL345)	+= adxl345.o
>  
>  obj-$(CONFIG_SENSORS_APPLESMC)	+= applesmc.o
>  obj-$(CONFIG_SENSORS_AMS)	+= ams/
> Index: drivers/hwmon/Kconfig
> ===================================================================
> --- linux-2.6.29.3-orig/drivers/hwmon/Kconfig	(revision 33)
> +++ linux-2.6.29.3/drivers/hwmon/Kconfig	(revision 49)
> @@ -199,6 +199,16 @@
>  	  This driver can also be build as a module.  If so, the module
>  	  will be called adt7475.
>  
> +config SENSORS_ADXL345
> +	tristate "Analog Devices ADXL345"
> +	depends on I2C && EXPERIMENTAL
> +	help
> +	  If you say yes here, you get support for the Analog Devices
> +	  ADXL345 digital accelerometer chip.
> +
> +	  This driver can also be build as a module.  If so, the module
> +	  will be called adxl345.
> +
>  config SENSORS_K8TEMP
>  	tristate "AMD Athlon64/FX or Opteron temperature sensor"
>  	depends on X86 && PCI && EXPERIMENTAL
> Index: drivers/hwmon/adxl345.c
> ===================================================================
> --- linux-2.6.29.3-orig/drivers/hwmon/adxl345.c	(revision 0)
> +++ linux-2.6.29.3/drivers/hwmon/adxl345.c	(revision 49)
> @@ -0,0 +1,521 @@
> +/*
> + * A hwmon driver for the Analog Devices ADXL345
> + *
> + * Copyright (c) 2009 Cyber Switching, Inc.
> + * Author: Robert Mehranfar <robertme@...thlink.net>
> + *
> + * 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/slab.h>
> +#include <linux/jiffies.h>
> +#include <linux/i2c.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/hwmon-vid.h>
> +#include <linux/err.h>
> +#include <linux/mutex.h>
> +#include <linux/kernel.h>
> +
> +#define DRV_NAME	"adxl345"
> +#define DRV_VERSION	"0.1"
> +
> +#define SIMULATE 1
> +
> +/*
> + * The ADXL345 registers
> + */
> +#define ADXL345_REG_DEV_ID		0x00
> +#define ADXL345_REG_OFS(nr)		(0x1E + (nr))
> +#define ADXL345_REG_DATA(nr)		(0x32 + (nr))
> +#define ADXL345_REG_DATA_FORMAT		0x31
> +
> +/*
> + * See ADXL345 specification
> + */
> +#define OFFSET_SCALE_FACTOR_WHOLE 15
> +#define OFFSET_SCALE_FACTOR_FRACTIONAL 6
> +
> +#define MAX_OFFSET 1988
> +#define MIN_OFFSET -1998
> +
> +/*
> + * Based on 10-bit resolution +/-16 range set in the DATA FORMAT
> register
> + */
> +#define DATA_SCALE_FACTOR_WHOLE 15
> +#define DATA_SCALE_FACTOR_FRACTIONAL 6
> +#define NUMBER_OF_AXES 3
> +
> +#define X_AXIS 0
> +#define Y_AXIS 1
> +#define Z_AXIS 2
> +
> +/* Position in the sysfs attribute array */
> +#define X_AXIS_ATTR 0
> +#define Y_AXIS_ATTR 1
> +#define Z_AXIS_ATTR 2
> +#define DATA_ATTR 3
> +
> +/*
> + * Functions declaration
> + */
> +static void adxl345_init_client(struct i2c_client *client);
> +static struct adxl345_data *adxl345_update_device(struct device *dev);
> +static void convert_to_fraction(s16 data, u8 whole_scale, u8
> fraction_scale,
> +					int *decimal, int *fraction);
> +
> +/*
> + * Client data (each client gets its own)
> + */
> +struct adxl345_data {
> +	struct i2c_client	client;
> +	struct device		*hwmon_dev;
> +	struct mutex		update_lock;	/* lock on the structure
> */
> +	char			valid;		/* 0 until below are
> valid */
> +	unsigned long		last_updated;	/* in jiffies */
> +
> +	/*
> +	 * ADXL345 Data
> +	 * In two's complement, data coming in from or going out to
> user-space
> +	 * must be converted.
> +	 */
> +	u8			offset[NUMBER_OF_AXES];
> +	u16			data[NUMBER_OF_AXES];
> +};
> +
> +
> +/*
> + * Converts internal data to a decimal-fraction value.
> + * Notes: Must already be converted out of twos complement
> + *
> + * @param data  Data to be converted
> + * @param whole_scale Scale factor for whole number part. (Set to 1 for
> no scaling).
> + * @param fraction_scale Scale factor for fractional number part. (Set
> to 1 for no scaling).
> + * @param decimal Pointer to location to store decimal part.
> + * @param fraction Pointer to location to store fractional part.
> + */
> +static void convert_to_fraction(s16 data, u8 whole_scale, u8
> fraction_scale,
> +					int *decimal, int *fraction)
> +{
> +	int temp_decimal, temp_fraction, temp;
> +	int sign = 1;
> +
> +	/* Scale the decimal and fractional parts */
> +	temp_decimal = data * whole_scale * 10;
> +	temp_fraction = data * fraction_scale;
> +
> +	/* get rid of the sign for negative fractions */
> +	if (temp_fraction < 0) {
> +		sign = -1;
> +		temp_fraction *= sign;
> +	}
> +
> +	/* If necessary, carry */
> +	if (temp_fraction >= 10) {
> +		/* Add to the decimal part */
> +		temp_decimal += sign * temp_fraction;
> +
> +		/* Amount to be subtracted from the fractional part */
> +		temp = temp_fraction / 10;
> +
> +		temp_fraction -= temp * 10;
> +	}
> +
> +	temp_decimal /= 10;
> +
> +	/*
> +	 * If at least 10 still remains in the fractional part, one
> +	 * last carry
> +	 */
> +	if (temp_fraction >= 10) {
> +		temp_decimal += sign;
> +		temp_fraction -= 10;
> +	}
> +
> +	/* Pass the values up */
> +	*decimal = temp_decimal;
> +	*fraction = temp_fraction;
> +}
> +
> +/*
> + * Called in response to cat ofs(x,y,z) in sysfs
> + *
> + * @param dev Pointer to device
> + * @param attr Pointer to the device attributes
> + * @param buf Pointer to string shown in user space
> + * @return Number of chars copied to buffer
> +*/
> +static ssize_t show_offset(struct device *dev,
> +				struct device_attribute *attr,
> +				char *buf)
> +{
> +	int index = to_sensor_dev_attr(attr)->index;
> +	struct adxl345_data *data = adxl345_update_device(dev);
> +	int decimal, fraction;
> +	s8 temp_data;
> +
> +	dev_dbg(dev, "%s\n", __func__);
> +
> +	/* Convert from 2's complement */
> +	temp_data = ~(data->offset[index] - 1);
> +
> +	dev_dbg(dev, "temp_data=%d\n", temp_data);
> +
> +	convert_to_fraction(temp_data,
> +			OFFSET_SCALE_FACTOR_WHOLE,
> +			OFFSET_SCALE_FACTOR_FRACTIONAL,
> +			&decimal,
> +			&fraction);
> +
> +	return snprintf(buf, PAGE_SIZE,
> +			"%4d.%1d\n", decimal, fraction);
> +}
> +
> +/*
> + * Called in response to echoing data to ofs(x,y,z) in sysfs
> + * Note: Input range is -1998 to 1998 milli-g's
> + *
> + * @param dev Pointer to device
> + * @param attr Pointer to the device attributes
> + * @param buf Pointer to string passed in from user space
> + * @param count Number of chars passed in from user space..
> + * @return Number of chars passed in from user space.
> + */
> +static ssize_t set_offset(struct device *dev,
> +				struct device_attribute *attr,
> +				const char *buf,
> +				size_t count)
> +{
> +	int index = to_sensor_dev_attr(attr)->index;
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct adxl345_data *data = i2c_get_clientdata(client);
> +	long val;
> +	long temp_val;
> +
> +	dev_dbg(dev, "%s\n", __func__);
> +
> +	if (!strict_strtol(buf, 10, &val)) {
> +		dev_dbg(dev, "error in converting string '%s' to
> long\n",
> +				buf);
> +		return 0;
> +	}
> +
> +	/* If outside offset range, clip to max or min value */
> +	if (val < MIN_OFFSET)
> +		val = MIN_OFFSET;
> +	else if (val > MAX_OFFSET)
> +		val = MAX_OFFSET;
> +
> +	temp_val = (val * 100) %
> +			((OFFSET_SCALE_FACTOR_WHOLE * 100) +
> +			(OFFSET_SCALE_FACTOR_FRACTIONAL * 10));
> +	if (temp_val < 0)
> +		temp_val *= -1;
> +
> +	/* Get rid of scale for internal storage */
> +	val = (val * 100) /
> +			((OFFSET_SCALE_FACTOR_WHOLE * 100) +
> +			(OFFSET_SCALE_FACTOR_FRACTIONAL * 10));
> +
> +	if (temp_val > (OFFSET_SCALE_FACTOR_WHOLE * 100) / 2 && val > 0)
> +		++val;
> +	else if (temp_val > (OFFSET_SCALE_FACTOR_WHOLE * 100) / 2 && val
> < 0)
> +		--val;
> +
> +	val = ~val + 1;  /* convert to two's complement */
> +
> +	mutex_lock(&data->update_lock);
> +
> +	data->offset[index] = val;
> +
> +	dev_dbg(dev, "offset[%d]=%d\n", index, data->offset[index]);
> +
> +	/* Write the avlue to the chip via I2C */
> +	i2c_smbus_write_byte_data(client,
> +			ADXL345_REG_OFS(index),
> +			data->offset[index]);
> +
> +	mutex_unlock(&data->update_lock);
> +
> +	return count;
> +}
> +
> +/*
> + * Called in response to cat data in sysfs
> + *
> + * @param dev Pointer to device
> + * @param attr Pointer to the device attributes
> + * @param buf Pointer to string shown in user space
> + * @return Number of chars copied to buffer
> +*/
> +static ssize_t show_data(struct device *dev, struct device_attribute
> *attr,
> +				char *buf)
> +{
> +	int i;
> +	s16 temp_data;
> +	int decimal[NUMBER_OF_AXES], fraction[NUMBER_OF_AXES];
> +
> +	struct adxl345_data *data = adxl345_update_device(dev);
> +
> +	/* Convert x,y,z values */
> +	for (i = 0; i < NUMBER_OF_AXES; i++) {
> +		/* Convert from 2's complement */
> +		temp_data = ~(data->data[i] - 1);
> +
> +		convert_to_fraction(temp_data,
> +				DATA_SCALE_FACTOR_WHOLE,
> +				DATA_SCALE_FACTOR_FRACTIONAL,
> +				&decimal[i],
> +				&fraction[i]);
> +	}
> +
> +	return snprintf(buf, PAGE_SIZE,
> +			"x:%5d.%1d y:%5d.%1d z:%5d.%1d\n",
> +			decimal[X_AXIS], fraction[X_AXIS],
> +			decimal[Y_AXIS], fraction[Y_AXIS],
> +			decimal[Z_AXIS], fraction[Z_AXIS]);
> +}
> +
> +/*  Attributes of the sysfs entries */
> +static SENSOR_DEVICE_ATTR(ofsx, S_IWUSR | S_IRUGO,
> +				show_offset, set_offset, X_AXIS_ATTR);
> +static SENSOR_DEVICE_ATTR(ofsy, S_IWUSR | S_IRUGO,
> +				show_offset, set_offset, Y_AXIS_ATTR);
> +static SENSOR_DEVICE_ATTR(ofsz, S_IWUSR | S_IRUGO,
> +				show_offset, set_offset, Z_AXIS_ATTR);
> +static SENSOR_DEVICE_ATTR(data, S_IRUGO,
> +				show_data, NULL, DATA_ATTR);
> +
> +static struct attribute *adxl345_attributes[] = {
> +	&sensor_dev_attr_ofsx.dev_attr.attr,
> +	&sensor_dev_attr_ofsy.dev_attr.attr,
> +	&sensor_dev_attr_ofsz.dev_attr.attr,
> +	&sensor_dev_attr_data.dev_attr.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group adxl345_group = {
> +	.attrs = adxl345_attributes,
> +};
> +
> +/*
> + * Initialize the chip
> + *
> + * @param client Pointer to the client structure
> + */
> +static void adxl345_init_client(struct i2c_client *client)
> +{
> +	dev_dbg(&client->dev, "%s\n", __func__);
> +
> +	/*
> +	 * Set up the device, No self test, Dont care about SPI or
> +	 * interrupt, 10 bit resoltion, +/- 16g range
> +	 */
> +	i2c_smbus_write_byte_data(client, ADXL345_REG_DATA_FORMAT,
> 0x03);
> +}
> +
> +/*
> + * Does more than just detection. If detection succeeds, it also
> + * registers the new chip.
> + *
> + * @param adapter Pointer to the adapter
> + * @param address I2C address
> + * @return Zero, upon success
> + */
> +static int adxl345_probe(struct i2c_client *client,
> +				const struct i2c_device_id *id)
> +{
> +	struct adxl345_data *data;
> +	int err = 0;
> +	u8 dev_id;
> +
> +	dev_dbg(&client->dev, "%s\n", __func__);
> +
> +	if (!i2c_check_functionality(client->adapter,
> I2C_FUNC_SMBUS_BYTE_DATA))
> +		return -ENODEV;
> +
> +	data = kzalloc(sizeof(struct adxl345_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(client, data);
> +
> +	#ifdef SIMULATE
> +	dev_id = 0xE5; /* Spoof the Analog Devices device ID */
> +	dev_dbg(&client->dev, "Simulating ADXL345 device\n");
> +	#else
> +	dev_id = i2c_smbus_read_byte_data(client, ADXL345_REG_DEV_ID);
> +	#endif
> +
> +	/* If the chip is not from Analog Devices, report an error */
> +	if (dev_id != 0xE5) {
> +		dev_err(&client->dev, "Unsupported chip
> (dev_id=0x%02X)\n",
> +				dev_id);
> +		err = -EINVAL;
> +		goto err_free_mem;
> +	}
> +
> +	dev_info(&client->dev, "chip found, driver version "
> +			DRV_VERSION "\n");
> +
> +	/* We can fill in the remaining client fields */
> +	mutex_init(&data->update_lock);
> +
> +	/* Initialize the ADXL345 chip */
> +	adxl345_init_client(client);
> +
> +	/* Register sysfs hooks */
> +	err = sysfs_create_group(&client->dev.kobj, &adxl345_group);
> +	if (err)
> +		goto err_free_mem;
> +
> +	data->hwmon_dev = hwmon_device_register(&client->dev);
> +	if (IS_ERR(data->hwmon_dev)) {
> +		err = PTR_ERR(data->hwmon_dev);
> +		goto err_remove;
> +	}
> +
> +	return 0;
> +
> +err_remove:
> +	sysfs_remove_group(&client->dev.kobj, &adxl345_group);
> +err_free_mem:
> +	kfree(data);
> +
> +	return err;
> +}
> +
> +/*
> + * Unregister device, remove the sysfs entries, and detach the client
> + * from I2C bus.
> + *
> + * @param client Pointer to the client structure
> + * @return Zero, upon success.
> + */
> +static int adxl345_remove(struct i2c_client *client)
> +{
> +	struct adxl345_data *data = i2c_get_clientdata(client);
> +
> +	hwmon_device_unregister(data->hwmon_dev);
> +	sysfs_remove_group(&client->dev.kobj, &adxl345_group);
> +
> +	i2c_unregister_device(client);
> +
> +	kfree(data);
> +
> +	return 0;
> +}
> +
> +/*
> + * Gets the data from the chip.
> + *
> + * @param client Pointer to the device
> + * @return Pointer to structure containing the data
> + */
> +static struct adxl345_data *adxl345_update_device(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct adxl345_data *data = i2c_get_clientdata(client);
> +	int i;
> +
> +	dev_dbg(dev, "%s\n", __func__);
> +
> +	mutex_lock(&data->update_lock);
> +
> +	/*
> +	 * This delay is 500ms, based on a default value of 100 for HZ
> +	 * in ARM kernels
> +	 */
> +	if (time_after(jiffies, data->last_updated + HZ * 50) ||
> +		!data->valid) {
> +		for (i = 0; i < NUMBER_OF_AXES; i++) {
> +			data->offset[i] =
> i2c_smbus_read_byte_data(client,
> +						ADXL345_REG_OFS(i));
> +			dev_dbg(dev, "offset[%d]=%d\n", i,
> data->offset[i]);
> +		}
> +
> +		/*
> +		 * Concatenate the data from each register pair
> +		 * Indexing logic is needed as per ADXL345 spec, LSB is
> first
> +		 * INDEX(reg)  LSB  MSB
> +		 *     0        0    1
> +		 *     1        2    3
> +		 *     2        4    5
> +		 */
> +		for (i = 0; i < NUMBER_OF_AXES; i++) {
> +			/* Get the MSB, shift by 8, and then get the LSB
> */
> +			data->data[i] = i2c_smbus_read_byte_data(client,
> +						ADXL345_REG_DATA(i*2+1))
> << 8;
> +			data->data[i] |=
> i2c_smbus_read_byte_data(client,
> +						ADXL345_REG_DATA(i*2));
> +
> +			dev_dbg(dev, "data[%d]=%d\n", i, data->data[i]);
> +		}
> +
> +		data->last_updated = jiffies;
> +		data->valid = 1;
> +	}
> +
> +	mutex_unlock(&data->update_lock);
> +
> +	return data;
> +}
> +
> +/*
> + * Driver data (common to all clients)
> + */
> +
> +static const struct i2c_device_id adxl345_id[] = {
> +	{ "adxl345", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, adxl345_id);
> +
> +static struct i2c_driver adxl345_driver = {
> +	.driver = {
> +		.name	= DRV_NAME,
> +	},
> +	.probe		= adxl345_probe,
> +	.remove		= adxl345_remove,
> +	.id_table	= adxl345_id,
> +};
> +
> +/*
> + * Initialize the module
> + *
> + * @return Zero, upon success
> + */
> +static int __init adxl345_init(void)
> +{
> +	return i2c_add_driver(&adxl345_driver);
> +}
> +
> +/*
> + * Remove the module
> + */
> +static void __exit adxl345_exit(void)
> +{
> +	i2c_del_driver(&adxl345_driver);
> +}
> +
> +MODULE_AUTHOR("Robert Mehranfar <robertme@...thlink.net>");
> +MODULE_DESCRIPTION("Analog Devices ADXL345 driver");
> +MODULE_LICENSE("GPL");
> +MODULE_VERSION(DRV_VERSION);
> +
> +module_init(adxl345_init);
> +module_exit(adxl345_exit);
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> lm-sensors mailing list
> lm-sensors@...sensors.org
> http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

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