Re: [PATCH] hmc6352: Add driver for the HMC6352 compass

[Jonathan Cameron <jic23-KWPb1pKIrIJaa/9Udqfwiw@public.gmane.org>]

On 06/17/10 12:50, Alan Cox wrote:
>>> +	struct i2c_msg msg1[] = {
>>> +		{ client->addr, 0, 1, &cmd1 },
>>> +	};
>>
>> It's quite overkill IMHO to have two messages here. In the end you send
>> only one. It would make sense if you made these messages static const,
> 
> They can't be const but I cleaned it up based on your other suggestions and
> then jumped up and down on it a bit more.
> 
> 
> hmc6352: Add driver for the HMC6352 compass
> 
> From: Kalhan Trisal <kalhan.trisal-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> 
> This driver will report the heading values in degrees to the sysfs interface.
> The values returned are headings . e.g. 245.6
> 
> Cleanups requested now all folded in and a sysfs description to keep Andrew
> happy.
> 
> Signed-off-by: Kalhan Trisal <kalhan.trisal-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Alan Cox <alan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Hi Alan,

I guess it is pretty unlikely anyone would ever have more than one compass and
if they do they can deal with the mutex sharing if they care.

I think there is a small issue where the code and documentation don't match
for the calibration attribute.  The version in the docs makes more sense to
me and I think it will slightly simplify the code.  

Fix that and I'm happy to add:
Acked-by: Jonathan Cameron <jic23-KWPb1pKIrIJaa/9Udqfwiw@public.gmane.org>

> ---
> 
>  .../ABI/testing/sysfs-bus-i2c-devices-hm6352       |   21 +++
>  drivers/misc/Kconfig                               |    7 +
>  drivers/misc/Makefile                              |    1 
>  drivers/misc/hmc6352.c                             |  165 ++++++++++++++++++++
>  4 files changed, 194 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-i2c-devices-hm6352
>  create mode 100644 drivers/misc/hmc6352.c
> 
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-i2c-devices-hm6352 b/Documentation/ABI/testing/sysfs-bus-i2c-devices-hm6352
> new file mode 100644
> index 0000000..feb2e4a
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-i2c-devices-hm6352
> @@ -0,0 +1,21 @@
> +Where:		/sys/bus/i2c/devices/.../heading0_input
> +Date:		April 2010
> +Kernel Version: 2.6.36?
> +Contact:	alan.cox-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org
> +Description:	Reports the current heading from the compass as a floating
> +		point value in degrees.
> +
> +Where:		/sys/bus/i2c/devices/.../power_state
> +Date:		April 2010
> +Kernel Version: 2.6.36?
> +Contact:	alan.cox-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org
> +Description:	Sets the power state of the device. 0 sets the device into
> +		sleep mode, 1 wakes it up.
> +
> +Where:		/sys/bus/i2c/devices/.../calibration
> +Date:		April 2010
> +Kernel Version: 2.6.36?
> +Contact:	alan.cox-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org
> +Description:	Sets the calibration on or off (1 = on, 0 = off). See the
> +		chip data sheet.
I think there is a disrepancy between what is described here and what the code
does.  Looks to me like values are 1 for on and 2 for off in the code (which
is a little odd).


> +
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 26386a9..9e825cb 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -304,6 +304,13 @@ config SENSORS_TSL2550
>  	  This driver can also be built as a module.  If so, the module
>  	  will be called tsl2550.
>  
> +config HMC6352
> +	tristate "Honeywell HMC6352 compass"
> +	depends on I2C
> +	help
> +	  This driver provides support for the Honeywell HMC6352 compass,
> +	  providing configuration and heading data via sysfs.
> +
>  config EP93XX_PWM
>  	tristate "EP93xx PWM support"
>  	depends on ARCH_EP93XX
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 6ed06a1..48597df 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_DS1682)		+= ds1682.o
>  obj-$(CONFIG_TI_DAC7512)	+= ti_dac7512.o
>  obj-$(CONFIG_C2PORT)		+= c2port/
>  obj-$(CONFIG_IWMC3200TOP)      += iwmc3200top/
> +obj-$(CONFIG_HMC6352)		+= hmc6352.o
>  obj-y				+= eeprom/
>  obj-y				+= cb710/
>  obj-$(CONFIG_VMWARE_BALLOON)	+= vmware_balloon.o
> diff --git a/drivers/misc/hmc6352.c b/drivers/misc/hmc6352.c
> new file mode 100644
> index 0000000..3243c8c
> --- /dev/null
> +++ b/drivers/misc/hmc6352.c
> @@ -0,0 +1,165 @@
> +/*
> + * hmc6352.c - Honeywell Compass Driver
> + *
> + * Copyright (C) 2009 Intel Corp
> + *
> + *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + * 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; version 2 of the License.
> + *
> + * 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.,
> + * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/i2c.h>
> +#include <linux/err.h>
> +#include <linux/delay.h>
> +#include <linux/sysfs.h>
> +
> +static DEFINE_MUTEX(compass_mutex);
> +
> +static int compass_command(struct i2c_client *c, u8 cmd)
> +{
> +	int ret = i2c_master_send(c, &cmd, 1);
> +	if (ret < 0)
> +		dev_warn(&c->dev, "command '%c' failed.\n", cmd);
> +	return ret;
> +}
> +
> +static int compass_store(struct device *dev, const char *buf, size_t count,
> +			const char *map)
> +{
> +	struct i2c_client *c = to_i2c_client(dev);
> +	int ret;
> +	unsigned long val;
> +
> +	if (strict_strtoul(buf, 10, &val))
> +		return -EINVAL;
> +	if (val < 0 || val >= strlen(map) || map[val] == ' ')
> +		return -EINVAL;
> +	mutex_lock(&compass_mutex);
> +	ret = compass_command(c, map[val]);
> +	mutex_unlock(&compass_mutex);
> +	return ret;
> +}
> +
> +static ssize_t compass_calibration_store(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t count)
> +{
> +	return compass_store(dev, buf, count, " CE");
> +}	
> +
> +static ssize_t compass_power_mode_store(struct device *dev,
> +		struct device_attribute *attr, const  char *buf, size_t count)
> +{
> +	return compass_store(dev, buf, count, "SW");
> +}
> +
> +static ssize_t compass_heading_data_show(struct device *dev,
> +			struct device_attribute *attr, char *buf)
> +{
> +
> +	struct i2c_client *client = to_i2c_client(dev);
> +	unsigned char i2c_data[2];
> +	unsigned int ret;
> +
> +	mutex_lock(&compass_mutex);
> +	ret = compass_command(client, 'A');
> +	if (ret != 1) {
> +		mutex_unlock(&compass_mutex);
> +		return ret;
> +	}
> +	msleep(10); /* sending 'A' cmd we need to wait for 7-10 millisecs */
> +	ret = i2c_master_recv(client, i2c_data, 2);
> +	mutex_unlock(&compass_mutex);
> +	if (ret != 1) {
> +		dev_warn(dev, "i2c read data cmd failed\n");
> +		return ret;
> +	}
> +	ret = (i2c_data[0] << 8) | i2c_data[1];
> +	return sprintf(buf, "%d.%d\n", ret/10, ret%10);
> +}
> +
If we are being ludicrously fussy, no point in 2 blank lines here...
> +
> +static DEVICE_ATTR(heading0_input, S_IRUGO, compass_heading_data_show, NULL);
> +static DEVICE_ATTR(calibration, S_IWUSR, NULL, compass_calibration_store);
> +static DEVICE_ATTR(power_state, S_IWUSR, NULL, compass_power_mode_store);
> +
> +static struct attribute *mid_att_compass[] = {
> +	&dev_attr_heading0_input.attr,
> +	&dev_attr_calibration.attr,
> +	&dev_attr_power_state.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group m_compass_gr = {
> +	.name = "hmc6352",
> +	.attrs = mid_att_compass
> +};
> +
> +static int hmc6352_probe(struct i2c_client *client,
> +					const struct i2c_device_id *id)
> +{
> +	int res;
> +
> +	res = sysfs_create_group(&client->dev.kobj, &m_compass_gr);
> +	if (res) {
> +		dev_err(&client->dev, "device_create_file failed\n");
> +		return res;
> +	}
> +	dev_info(&client->dev, "%s HMC6352 compass chip found\n",
> +							client->name);
> +	return 0;
> +}
> +
> +static int hmc6352_remove(struct i2c_client *client)
> +{
> +	sysfs_remove_group(&client->dev.kobj, &m_compass_gr);
> +	return 0;
> +}
> +
> +static struct i2c_device_id hmc6352_id[] = {
> +	{ "hmc6352", 0 },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, hmc6352_id);
> +
> +static struct i2c_driver hmc6352_driver = {
> +	.driver = {
> +		.name = "hmc6352",
> +	},
> +	.probe = hmc6352_probe,
> +	.remove = hmc6352_remove,
> +	.id_table = hmc6352_id,
> +};
> +
> +static int __init sensor_hmc6352_init(void)
> +{
> +	return i2c_add_driver(&hmc6352_driver);
> +}
> +
> +static void  __exit sensor_hmc6352_exit(void)
> +{
> +	i2c_del_driver(&hmc6352_driver);
> +}
> +
> +module_init(sensor_hmc6352_init);
> +module_exit(sensor_hmc6352_exit);
> +
> +MODULE_AUTHOR("Kalhan Trisal <kalhan.trisal-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org");
> +MODULE_DESCRIPTION("hmc6352 Compass Driver");
> +MODULE_LICENSE("GPL v2");
> 
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