[lm-sensors] [PATCH] hwmon: Add LTC4245 driver

Jean Delvare khali at linux-fr.org
Tue Oct 21 14:19:40 CEST 2008


Hi Ira, hi Hans,

On Mon, 20 Oct 2008 09:03:08 -0700, Ira Snyder wrote:
> Add Linux support for the Linear Technology LTC4245 Multiple Supply Hot
> Swap controller I2C monitoring interface.
> 
> Signed-off-by: Ira W. Snyder <iws at ovro.caltech.edu>
> ---
> 
> I'm pretty sure this should be the final revision of the driver. Please
> go ahead and forward it upstream. :)
> 
> I apologize for the late response. I was having some troubles with my
> email. They should all be sorted out now.
> 
> Thanks for all the help and review!
> Ira
> 
> 
> Changes v3 -> v4:
>   * simplify ltc4245_get_voltage(), removing special casing for -12v
>   * power should always be a positive value
> 
> Changes v2 -> v3:
>   * fix units (power?_input in uW, curr?_input in mA)
>   * combine all alarm functions
>   * rename power[1-4]_alarm to in[5-8]_min_alarm, per suggestions
> 
> Changes v1 -> v2:
>   * fixed checkpatch warnings
>   * removed raw register access, per suggestions
>   * changed sysfs interface, per suggestions (current, power, alarms)

Hans, thanks a lot for the reviews. Ira, thanks for going through all
the iterations patiently. My turn now:

> 
> 
>  Documentation/hwmon/ltc4245 |   69 +++++
>  drivers/hwmon/Kconfig       |   11 +
>  drivers/hwmon/Makefile      |    1 +
>  drivers/hwmon/ltc4245.c     |  574 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 655 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/hwmon/ltc4245
>  create mode 100644 drivers/hwmon/ltc4245.c
> 
> diff --git a/Documentation/hwmon/ltc4245 b/Documentation/hwmon/ltc4245
> new file mode 100644
> index 0000000..d2f411a
> --- /dev/null
> +++ b/Documentation/hwmon/ltc4245
> @@ -0,0 +1,69 @@
> +Kernel driver ltc4245
> +=====================
> +
> +Supported chips:
> +  * Linear Technology LTC4245
> +    Prefix: 'ltc4245'
> +    Addresses scanned: 0x20-0x3f
> +    Datasheet:
> +        http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517
> +
> +Author: Ira W. Snyder <iws at ovro.caltech.edu>
> +
> +
> +Description
> +-----------
> +
> +The LTC4245 controller allows a board to be safely inserted and removed
> +from a live backplane in multiple supply systems such as CompactPCI and
> +PCI Express.
> +
> +
> +Sysfs entries
> +-------------
> +
> +The LTC4245 has built-in limits for over and under current warnings. This
> +makes it very likely that the reference circuit will be used.
> +
> +This driver uses the values in the datasheet to change the register values
> +into the values specified in the sysfs-interface document. The current readings
> +rely on the sense resistors listed in Table 2: "Sense Resistor Values".
> +
> +in1_input		12v input voltage (mV)
> +in2_input		5v  input voltage (mV)
> +in3_input		3v  input voltage (mV)
> +in4_input		Vee (-12v) input voltage (mV)
> +
> +in1_min_alarm		12v input undervoltage alarm
> +in2_min_alarm		5v  input undervoltage alarm
> +in3_min_alarm		3v  input undervoltage alarm
> +in4_min_alarm		Vee (-12v) input undervoltage alarm
> +
> +curr1_input		12v current (mA)
> +curr2_input		5v  current (mA)
> +curr3_input		3v  current (mA)
> +curr4_input		Vee (-12v) current (mA)
> +
> +curr1_max_alarm		12v overcurrent alarm
> +curr2_max_alarm		5v  overcurrent alarm
> +curr3_max_alarm		3v  overcurrent alarm
> +curr4_max_alarm		Vee (-12v) overcurrent alarm
> +
> +in5_input		12v output voltage (mV)
> +in6_input		5v  output voltage (mV)
> +in7_input		3v  output voltage (mV)
> +in8_input		Vee (-12v) output voltage (mV)
> +
> +in5_min_alarm		12v output undervoltage alarm
> +in6_min_alarm		5v  output undervoltage alarm
> +in7_min_alarm		3v  output undervoltage alarm
> +in8_min_alarm		Vee (-12v) output undervoltage alarm

I find it a bit weird to have alarms for limits which do not have sysfs
files themselves. If we know the limits, we could expose them as
read-only attributes (in a future patch)?

> +
> +in9_input		GPIO #1 voltage data
> +in10_input		GPIO #2 voltage data
> +in11_input		GPIO #3 voltage data
> +
> +power1_input		12v power usage (mW)
> +power2_input		5v  power usage (mW)
> +power3_input		3v  power usage (mW)
> +power4_input		Vee (-12v) power usage (mW)
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index d402e8d..91bec8a 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -836,6 +836,17 @@ config SENSORS_APPLESMC
>  	  Say Y here if you have an applicable laptop and want to experience
>  	  the awesome power of applesmc.
>  
> +config SENSORS_LTC4245
> +	tristate "Linear Technology LTC4245"
> +	depends on I2C && EXPERIMENTAL
> +	default n
> +	help
> +	  If you say yes here you get support for Linear Technology LTC4245
> +	  Multiple Supply Hot Swap Controller I2C interface.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called ltc4245.
> +
>  config HWMON_DEBUG_CHIP
>  	bool "Hardware Monitoring Chip debugging messages"
>  	default n
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 950134a..0ed56ac 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -59,6 +59,7 @@ obj-$(CONFIG_SENSORS_LM87)	+= lm87.o
>  obj-$(CONFIG_SENSORS_LM90)	+= lm90.o
>  obj-$(CONFIG_SENSORS_LM92)	+= lm92.o
>  obj-$(CONFIG_SENSORS_LM93)	+= lm93.o
> +obj-$(CONFIG_SENSORS_LTC4245)	+= ltc4245.o
>  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
>  obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
>  obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
> diff --git a/drivers/hwmon/ltc4245.c b/drivers/hwmon/ltc4245.c
> new file mode 100644
> index 0000000..5d0528b
> --- /dev/null
> +++ b/drivers/hwmon/ltc4245.c
> @@ -0,0 +1,574 @@
> +/*
> + * Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
> + *
> + * Copyright (C) 2008 Ira W. Snyder <iws at ovro.caltech.edu>
> + *
> + * 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 driver is based on the ds1621 and ina209 drivers.
> + *
> + * Datasheet:
> + * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/err.h>
> +#include <linux/slab.h>
> +#include <linux/i2c.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +
> +/* Addresses to probe */
> +static unsigned short normal_i2c[] = {

Should be const.

> +	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
> +	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
> +	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
> +	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
> +	I2C_CLIENT_END};

That's a lot of addresses. This has several drawbacks:
* This can make driver loading very slow on systems with many I2C
  buses, especially as you read from a lot of registers in your detect
  function.
* Some of these addresses (0x30-0x3f) are known to be
  probing-unfriendly. With such a large range of probes, the risk that
  you hit a chip which misbehaves on probe is high.
* As the LTC4245 doesn't have dedicated identification registers, you
  have to rely on heuristics, which may yield to false positives. I see
  that you have gone to quite some extent to make detection as good as
  possible, however the LTC4245 isn't the only chip out there which
  ignores the high bits of the register address, and checking for bits
  being 0 isn't terribly reliable (most I2C devices return 0x00 as the
  value of unused registers.)

So I'd rather limit the probing to addresses where the LTC4245 is
commonly found. Or even drop probing entirely. I don't expect these
chips to appear on mainstream hardware, probably it is only used in
specialized equipment, and there you know at which address it lives so
you don't need to probe for it? I would hope that you can simply
instantiate the i2c client explicitly where needed.

> +
> +/* Insmod parameters */
> +I2C_CLIENT_INSMOD_1(ltc4245);
> +
> +/* Here are names of the chip's registers (a.k.a. commands) */
> +enum ltc4245_cmd {
> +	LTC4245_STATUS			= 0x00, /* readonly */
> +	LTC4245_ALERT			= 0x01,
> +	LTC4245_CONTROL			= 0x02,
> +	LTC4245_ON			= 0x03,
> +	LTC4245_FAULT1			= 0x04,
> +	LTC4245_FAULT2			= 0x05,
> +	LTC4245_GPIO			= 0x06,
> +	LTC4245_ADCADR			= 0x07,
> +
> +	LTC4245_12VIN			= 0x10,
> +	LTC4245_12VSENSE		= 0x11,
> +	LTC4245_12VOUT			= 0x12,
> +	LTC4245_5VIN			= 0x13,
> +	LTC4245_5VSENSE			= 0x14,
> +	LTC4245_5VOUT			= 0x15,
> +	LTC4245_3VIN			= 0x16,
> +	LTC4245_3VSENSE			= 0x17,
> +	LTC4245_3VOUT			= 0x18,
> +	LTC4245_VEEIN			= 0x19,
> +	LTC4245_VEESENSE		= 0x1a,
> +	LTC4245_VEEOUT			= 0x1b,
> +	LTC4245_GPIOADC1		= 0x1c,
> +	LTC4245_GPIOADC2		= 0x1d,
> +	LTC4245_GPIOADC3		= 0x1e,
> +};
> +
> +struct ltc4245_data {
> +	struct device *hwmon_dev;
> +
> +	struct mutex update_lock;
> +	bool valid;
> +	unsigned long last_updated; /* in jiffies */
> +
> +	/* Control registers */
> +	u8 cregs[0x08];
> +
> +	/* Voltage registers */
> +	u8 vregs[0x0f];
> +};
> +
> +/* All registers are byte-sized (8 bit) */
> +static s32 ltc4245_read_reg(struct i2c_client *client, u8 reg)
> +{
> +	return i2c_smbus_read_byte_data(client, reg);
> +}

This function doesn't strike me as very useful. At the very least it
should be declared inline, but it could as well be dropped.

> +
> +#if 0
> +static s32 ltc4245_write_reg(struct i2c_client *client, u8 reg, u8 val)
> +{
> +	return i2c_smbus_write_byte_data(client, reg, val);
> +}
> +#endif

Don't include this at all if you don't need it.

> +
> +static struct ltc4245_data *ltc4245_update_device(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct ltc4245_data *data = i2c_get_clientdata(client);
> +	int i;
> +
> +	mutex_lock(&data->update_lock);
> +
> +	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
> +
> +		dev_dbg(&client->dev, "Starting ltc4245 update\n");
> +
> +		/* Read control registers -- 0x00 to 0x07 */
> +		for (i = 0; i < ARRAY_SIZE(data->cregs); i++)
> +			data->cregs[i] = ltc4245_read_reg(client, i);
> +
> +		/* Read voltage registers -- 0x10 to 0x1f */
> +		for (i = 0; i < ARRAY_SIZE(data->vregs); i++)
> +			data->vregs[i] = ltc4245_read_reg(client, i+0x10);
> +
> +		data->last_updated = jiffies;
> +		data->valid = 1;
> +	}
> +
> +	mutex_unlock(&data->update_lock);
> +
> +	return data;
> +}
> +
> +/* Return the voltage from the given register in millivolts */
> +static int ltc4245_get_voltage(struct device *dev, u8 reg)
> +{
> +	struct ltc4245_data *data = ltc4245_update_device(dev);
> +	const s32 val = data->vregs[reg - 0x10];
> +	const u8 regval = val;
> +	u32 voltage = 0;
> +
> +	if (unlikely(val < 0))
> +		return 0;

It's not unlikely, it's impossible. data->vregs is an array of u8.

> +
> +	switch (reg) {
> +	case LTC4245_12VIN:
> +	case LTC4245_12VOUT:
> +		voltage = regval * 55;
> +		break;
> +	case LTC4245_5VIN:
> +	case LTC4245_5VOUT:
> +		voltage = regval * 22;
> +		break;
> +	case LTC4245_3VIN:
> +	case LTC4245_3VOUT:
> +		voltage = regval * 15;
> +		break;
> +	case LTC4245_VEEIN:
> +	case LTC4245_VEEOUT:
> +		voltage = regval * -55;
> +		break;
> +	case LTC4245_GPIOADC1:
> +	case LTC4245_GPIOADC2:
> +	case LTC4245_GPIOADC3:
> +		voltage = regval * 10;
> +		break;
> +	default:
> +		/* If we get here, the developer messed up */
> +		WARN_ON_ONCE(1);
> +		break;
> +	}

I am under the impression that a 11-element array of scaling factors
would work much better - but it's up to you.

> +
> +	return voltage;
> +}
> +
> +/* Return the current in the given sense register in milliAmperes */
> +static u32 ltc4245_get_current(struct device *dev, u8 reg)
> +{
> +	struct ltc4245_data *data = ltc4245_update_device(dev);
> +	const s32 val = data->vregs[reg - 0x10];
> +	const u8 regval = val;
> +	u32 voltage;
> +	u32 current;
> +
> +	if (unlikely(val) < 0)
> +		return 0;

Same as above, this simply can't happen.

> +
> +	/* The strange looking conversions that follow are fixed-point
> +	 * math, since we cannot do floating point in the kernel.
> +	 *
> +	 * Step 1: convert sense register to microVolts
> +	 * Step 2: convert voltage to milliAmperes
> +	 *
> +	 * If you play around with the V=IR equation, you come up with
> +	 * the following: X uV / Y mOhm == Z mA
> +	 *
> +	 * With the resistors that are fractions of a milliOhm, we multiply
> +	 * the voltage and resistance by 10, to shift the decimal point.
> +	 * Now we can use the normal division operator again.
> +	 */
> +
> +	switch (reg) {
> +	case LTC4245_12VSENSE:
> +		voltage = regval * 250; /* voltage in uV */
> +		current = voltage / 50; /* sense resistor 50 mOhm */
> +		break;
> +	case LTC4245_5VSENSE:
> +		voltage = regval * 125; /* voltage in uV */
> +		current = (voltage * 10) / 35; /* sense resistor 3.5 mOhm */
> +		break;
> +	case LTC4245_3VSENSE:
> +		voltage = regval * 125; /* voltage in uV */
> +		current = (voltage * 10) / 25; /* sense resistor 2.5 mOhm */
> +		break;
> +	case LTC4245_VEESENSE:
> +		voltage = regval * 250; /* voltage in uV */
> +		current = voltage / 100; /* sense resistor 100 mOhm */
> +		break;
> +	default:
> +		/* If we get here, the developer messed up */
> +		WARN_ON_ONCE(1);
> +		current = 0;
> +		break;
> +	}
> +
> +	return current;
> +}
> +
> +static ssize_t ltc4245_show_voltage(struct device *dev,
> +				    struct device_attribute *da,
> +				    char *buf)
> +{
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> +	const u32 voltage = ltc4245_get_voltage(dev, attr->index);
> +
> +	return snprintf(buf, PAGE_SIZE, "%d\n", voltage);

Seems inconsistent to store the voltage in a u32 and print it with %d.
As ltc4245_get_voltage() returns an int, why don't you declare voltage
an int as well?

> +}
> +
> +static ssize_t ltc4245_show_current(struct device *dev,
> +				    struct device_attribute *da,
> +				    char *buf)
> +{
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> +	const u32 current = ltc4245_get_current(dev, attr->index);
> +
> +	return snprintf(buf, PAGE_SIZE, "%u\n", current);
> +}
> +
> +static ssize_t ltc4245_show_power(struct device *dev,
> +				  struct device_attribute *da,
> +				  char *buf)
> +{
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> +	const u32 current = ltc4245_get_current(dev, attr->index);
> +	const u32 output_voltage = ltc4245_get_voltage(dev, attr->index+1);
> +
> +	/* current in mA * voltage in mV == power in uW */
> +	const unsigned int power = abs(output_voltage * current);

abs() is defined in <linux/kernel.h>, which you didn't include.

> +
> +	return snprintf(buf, PAGE_SIZE, "%u\n", power);
> +}
> +
> +static ssize_t ltc4245_show_alarm(struct device *dev,
> +					  struct device_attribute *da,
> +					  char *buf)
> +{
> +	struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
> +	struct ltc4245_data *data = ltc4245_update_device(dev);
> +	const s32 reg = data->cregs[attr->index];
> +	const u32 mask = attr->nr;
> +
> +	if (unlikely(reg < 0)) {
> +		memset(buf, 0, PAGE_SIZE); /* user should not see old data */
> +		return 0;
> +	}

Same as above, this simply can't happen.

And as a side note, you don't bother zeroing the rest of the page on
success, so I can't see why you insist on doing it on failure.

> +
> +	return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
> +}
> +
> +/* These macros are used below in constructing device attribute objects
> + * for use with sysfs_create_group() to make a sysfs device file
> + * for each register.
> + */
> +
> +#define LTC4245_VOLTAGE(name, ltc4245_cmd_idx) \
> +	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> +	ltc4245_show_voltage, NULL, ltc4245_cmd_idx)
> +
> +#define LTC4245_CURRENT(name, ltc4245_cmd_idx) \
> +	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> +	ltc4245_show_current, NULL, ltc4245_cmd_idx)
> +
> +#define LTC4245_POWER(name, ltc4245_cmd_idx) \
> +	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> +	ltc4245_show_power, NULL, ltc4245_cmd_idx)
> +
> +#define LTC4245_ALARM(name, mask, reg) \
> +	static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \
> +	ltc4245_show_alarm, NULL, (mask), reg)
> +
> +/* Construct a sensor_device_attribute structure for each register */
> +
> +/* Input voltages */
> +LTC4245_VOLTAGE(in1_input,			LTC4245_12VIN);
> +LTC4245_VOLTAGE(in2_input,			LTC4245_5VIN);
> +LTC4245_VOLTAGE(in3_input,			LTC4245_3VIN);
> +LTC4245_VOLTAGE(in4_input,			LTC4245_VEEIN);
> +
> +/* Input undervoltage alarms */
> +LTC4245_ALARM(in1_min_alarm,	(1 << 0),	LTC4245_FAULT1);
> +LTC4245_ALARM(in2_min_alarm,	(1 << 1),	LTC4245_FAULT1);
> +LTC4245_ALARM(in3_min_alarm,	(1 << 2),	LTC4245_FAULT1);
> +LTC4245_ALARM(in4_min_alarm,	(1 << 3),	LTC4245_FAULT1);
> +
> +/* Currents (via sense resistor) */
> +LTC4245_CURRENT(curr1_input,			LTC4245_12VSENSE);
> +LTC4245_CURRENT(curr2_input,			LTC4245_5VSENSE);
> +LTC4245_CURRENT(curr3_input,			LTC4245_3VSENSE);
> +LTC4245_CURRENT(curr4_input,			LTC4245_VEESENSE);
> +
> +/* Overcurrent alarms */
> +LTC4245_ALARM(curr1_max_alarm,	(1 << 4),	LTC4245_FAULT1);
> +LTC4245_ALARM(curr2_max_alarm,	(1 << 5),	LTC4245_FAULT1);
> +LTC4245_ALARM(curr3_max_alarm,	(1 << 6),	LTC4245_FAULT1);
> +LTC4245_ALARM(curr4_max_alarm,	(1 << 7),	LTC4245_FAULT1);
> +
> +/* Output voltages */
> +LTC4245_VOLTAGE(in5_input,			LTC4245_12VOUT);
> +LTC4245_VOLTAGE(in6_input,			LTC4245_5VOUT);
> +LTC4245_VOLTAGE(in7_input,			LTC4245_3VOUT);
> +LTC4245_VOLTAGE(in8_input,			LTC4245_VEEOUT);
> +
> +/* Power Bad alarms */
> +LTC4245_ALARM(in5_min_alarm,	(1 << 0),	LTC4245_FAULT2);
> +LTC4245_ALARM(in6_min_alarm,	(1 << 1),	LTC4245_FAULT2);
> +LTC4245_ALARM(in7_min_alarm,	(1 << 2),	LTC4245_FAULT2);
> +LTC4245_ALARM(in8_min_alarm,	(1 << 3),	LTC4245_FAULT2);
> +
> +/* GPIO voltages */
> +LTC4245_VOLTAGE(in9_input,			LTC4245_GPIOADC1);
> +LTC4245_VOLTAGE(in10_input,			LTC4245_GPIOADC2);
> +LTC4245_VOLTAGE(in11_input,			LTC4245_GPIOADC3);
> +
> +/* Power Consumption (virtual) */
> +LTC4245_POWER(power1_input,			LTC4245_12VSENSE);
> +LTC4245_POWER(power2_input,			LTC4245_5VSENSE);
> +LTC4245_POWER(power3_input,			LTC4245_3VSENSE);
> +LTC4245_POWER(power4_input,			LTC4245_VEESENSE);
> +
> +/* Finally, construct an array of pointers to members of the above objects,
> + * as required for sysfs_create_group()
> + */
> +static struct attribute *ltc4245_attributes[] = {
> +	&sensor_dev_attr_in1_input.dev_attr.attr,
> +	&sensor_dev_attr_in2_input.dev_attr.attr,
> +	&sensor_dev_attr_in3_input.dev_attr.attr,
> +	&sensor_dev_attr_in4_input.dev_attr.attr,
> +
> +	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
> +	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
> +	&sensor_dev_attr_in3_min_alarm.dev_attr.attr,
> +	&sensor_dev_attr_in4_min_alarm.dev_attr.attr,
> +
> +	&sensor_dev_attr_curr1_input.dev_attr.attr,
> +	&sensor_dev_attr_curr2_input.dev_attr.attr,
> +	&sensor_dev_attr_curr3_input.dev_attr.attr,
> +	&sensor_dev_attr_curr4_input.dev_attr.attr,
> +
> +	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
> +	&sensor_dev_attr_curr2_max_alarm.dev_attr.attr,
> +	&sensor_dev_attr_curr3_max_alarm.dev_attr.attr,
> +	&sensor_dev_attr_curr4_max_alarm.dev_attr.attr,
> +
> +	&sensor_dev_attr_in5_input.dev_attr.attr,
> +	&sensor_dev_attr_in6_input.dev_attr.attr,
> +	&sensor_dev_attr_in7_input.dev_attr.attr,
> +	&sensor_dev_attr_in8_input.dev_attr.attr,
> +
> +	&sensor_dev_attr_in5_min_alarm.dev_attr.attr,
> +	&sensor_dev_attr_in6_min_alarm.dev_attr.attr,
> +	&sensor_dev_attr_in7_min_alarm.dev_attr.attr,
> +	&sensor_dev_attr_in8_min_alarm.dev_attr.attr,
> +
> +	&sensor_dev_attr_in9_input.dev_attr.attr,
> +	&sensor_dev_attr_in10_input.dev_attr.attr,
> +	&sensor_dev_attr_in11_input.dev_attr.attr,
> +
> +	&sensor_dev_attr_power1_input.dev_attr.attr,
> +	&sensor_dev_attr_power2_input.dev_attr.attr,
> +	&sensor_dev_attr_power3_input.dev_attr.attr,
> +	&sensor_dev_attr_power4_input.dev_attr.attr,
> +
> +	NULL,
> +};
> +
> +static struct attribute_group ltc4245_group = {

Should be const.

> +	.attrs = ltc4245_attributes,
> +};
> +
> +static int ltc4245_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct ltc4245_data *data;
> +	int ret;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +
> +	if (!data) {

Coding style: no blank line between function call and error test.

> +		ret = -ENOMEM;
> +		goto out_kzalloc;
> +	}
> +
> +	i2c_set_clientdata(client, data);
> +	mutex_init(&data->update_lock);
> +
> +	/* Initialize the LTC4245 chip */
> +	/* TODO */
> +
> +	/* Register sysfs hooks */
> +	ret = sysfs_create_group(&client->dev.kobj, &ltc4245_group);
> +
> +	if (ret)

Same here...

> +		goto out_sysfs_create_group;
> +
> +	data->hwmon_dev = hwmon_device_register(&client->dev);
> +

... and here.

> +	if (IS_ERR(data->hwmon_dev)) {
> +		ret = PTR_ERR(data->hwmon_dev);
> +		goto out_hwmon_device_register;
> +	}
> +
> +	return 0;
> +
> +out_hwmon_device_register:
> +	sysfs_remove_group(&client->dev.kobj, &ltc4245_group);
> +out_sysfs_create_group:
> +	kfree(data);
> +out_kzalloc:
> +	return ret;
> +}
> +
> +static int ltc4245_remove(struct i2c_client *client)
> +{
> +	struct ltc4245_data *data = i2c_get_clientdata(client);
> +
> +	hwmon_device_unregister(data->hwmon_dev);
> +	sysfs_remove_group(&client->dev.kobj, &ltc4245_group);
> +
> +	kfree(data);
> +
> +	return 0;
> +}
> +
> +/* Check that some bits in a control register appear at all possible
> + * locations without changing value
> + *
> + * @client: the i2c client to use
> + * @reg: the register to read
> + * @bits: the bits to check (0xff checks all bits,
> + *                           0x03 checks only the last two bits)
> + *
> + * return -ENODEV if the register value doesn't stay constant at all
> + * possible addresses
> + *
> + * return 0 for success
> + */
> +static int ltc4245_check_control_reg(struct i2c_client *client, u8 reg, u8 bits)
> +{
> +	int i;
> +	s32 v, voff1, voff2;
> +
> +	v = ltc4245_read_reg(client, reg) & bits;

ltc4245_read_reg may return an error. Masking error values usually
isn't what you want ;) Check for < 0 first and mask only after that.
Same problem below.

> +
> +	if (v < 0)
> +		return -ENODEV;
> +
> +	for (i = 0x00; i < 0xff; i += 0x20) {
> +		voff1 = ltc4245_read_reg(client, reg + i) & bits;
> +		voff2 = ltc4245_read_reg(client, reg + i + 0x08) & bits;
> +
> +		if (voff1 < 0 || voff2 < 0 || v != voff1 || v != voff2)
> +			return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ltc4245_detect(struct i2c_client *client,
> +			  int kind,
> +			  struct i2c_board_info *info)
> +{
> +	struct i2c_adapter *adapter = client->adapter;
> +
> +	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
> +		return -ENODEV;
> +
> +	if (kind < 0) {		/* probed detection - check the chip type */
> +		s32 v;		/* 8 bits from the chip, or -ERRNO */
> +
> +		/* Chip registers 0x00-0x07 are control registers
> +		 * Chip registers 0x10-0x1f are data registers
> +		 *
> +		 * Address bits b7-b5 are ignored. This makes the chip "repeat"
> +		 * in steps of 0x20. Any control registers should appear with
> +		 * the same values across all duplicated addresses.
> +		 *
> +		 * Register 0x02 bit b2 is reserved, expect 0
> +		 * Register 0x07 bits b7 to b4 are reserved, expect 0
> +		 *
> +		 * Registers 0x01, 0x02 are control registers and should not
> +		 * change on their own.
> +		 *
> +		 * Register 0x06 bits b6 and b7 are control bits, and should
> +		 * not change on their own.
> +		 *
> +		 * Register 0x07 bits b3 to b0 are control bits, and should
> +		 * not change on their own.
> +		 */
> +
> +		/* read register 0x02 reserved bit, expect 0 */
> +		v = ltc4245_read_reg(client, LTC4245_CONTROL);

Note: you should never call device-specific read functions in detect
functions, as by definition you don't yet know which device you have.

> +		if (v < 0 || (v & 0x04) != 0)
> +			return -ENODEV;
> +
> +		/* read register 0x07 reserved bits, expect 0 */
> +		v = ltc4245_read_reg(client, LTC4245_ADCADR);
> +		if (v < 0 || (v & 0xf0) != 0)
> +			return -ENODEV;
> +
> +		/* check that the alert register appears at all locations */
> +		if (ltc4245_check_control_reg(client, LTC4245_ALERT, 0xff))
> +			return -ENODEV;
> +
> +		/* check that the control register appears at all locations */
> +		if (ltc4245_check_control_reg(client, LTC4245_CONTROL, 0xff))
> +			return -ENODEV;
> +
> +		/* check that register 0x06 bits b6 and b7 stay constant */
> +		if (ltc4245_check_control_reg(client, LTC4245_GPIO, 0xc0))
> +			return -ENODEV;
> +
> +		/* check that register 0x07 bits b3-b0 stay constant */
> +		if (ltc4245_check_control_reg(client, LTC4245_ADCADR, 0x0f))
> +			return -ENODEV;
> +	}
> +
> +	strlcpy(info->type, "ltc4245", I2C_NAME_SIZE);
> +	pr_info("ltc4245: %s on i2c-%u address 0x%02x\n",
> +			kind < 0 ? "probed" : "forced",
> +			adapter->nr, client->addr);

Please use dev_info(&adapter->dev, ...) instead.

> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id ltc4245_id[] = {
> +	{ "ltc4245", ltc4245 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc4245_id);
> +
> +/* This is the driver that will be inserted */
> +static struct i2c_driver ltc4245_driver = {
> +	.class		= I2C_CLASS_HWMON,
> +	.driver = {
> +		.name	= "ltc4245",
> +	},
> +	.probe		= ltc4245_probe,
> +	.remove		= ltc4245_remove,
> +	.id_table	= ltc4245_id,
> +	.detect		= ltc4245_detect,
> +	.address_data	= &addr_data,
> +};
> +
> +static int __init ltc4245_init(void)
> +{
> +	return i2c_add_driver(&ltc4245_driver);
> +}
> +
> +static void __exit ltc4245_exit(void)
> +{
> +	i2c_del_driver(&ltc4245_driver);
> +}
> +
> +MODULE_AUTHOR("Ira W. Snyder <iws at ovro.caltech.edu>");
> +MODULE_DESCRIPTION("LTC4245 driver");
> +MODULE_LICENSE("GPL");
> +
> +module_init(ltc4245_init);
> +module_exit(ltc4245_exit);


-- 
Jean Delvare




More information about the lm-sensors mailing list