[PATCH v3 0/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring

[PATCH v3 0/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring

[rentao.bupt]

From: Tao Ren <rentao.bupt@gmail.com>

The patch series adds hardware monitoring driver for the Maxim MAX127
chip.

Patch #1 adds the max127 hardware monitoring driver, and patch #2 adds
documentation for the driver.

Resending the patch series (v3) with XDP maintainers removed from to/cc
list to reduce noise.

Tao Ren (2):
  hwmon: (max127) Add Maxim MAX127 hardware monitoring driver
  docs: hwmon: Document max127 driver

 Documentation/hwmon/index.rst  |   1 +
 Documentation/hwmon/max127.rst |  45 +++++
 drivers/hwmon/Kconfig          |   9 +
 drivers/hwmon/Makefile         |   1 +
 drivers/hwmon/max127.c         | 346 +++++++++++++++++++++++++++++++++
 5 files changed, 402 insertions(+)
 create mode 100644 Documentation/hwmon/max127.rst
 create mode 100644 drivers/hwmon/max127.c

-- 
2.17.1

[PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[rentao.bupt]

From: Tao Ren <rentao.bupt@gmail.com>

Add hardware monitoring driver for the Maxim MAX127 chip.

MAX127 min/max range handling code is inspired by the max197 driver.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
---
 Changes in v3:
   - no code change. xdp maintainers were removed from to/cc list.
 Changes in v2:
   - replace devm_hwmon_device_register_with_groups() with
     devm_hwmon_device_register_with_info() API.
   - divide min/max read and write methods to separate functions.
   - fix raw-to-vin conversion logic.
   - refine ctrl_byte handling so mutex is not needed to protect the
     byte.
   - improve i2c_transfer() error handling.
   - a few other improvements (comments, variable naming, and etc.).

 drivers/hwmon/Kconfig  |   9 ++
 drivers/hwmon/Makefile |   1 +
 drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 356 insertions(+)
 create mode 100644 drivers/hwmon/max127.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 9d600e0c5584..716df51edc87 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -950,6 +950,15 @@ config SENSORS_MAX1111
 	  This driver can also be built as a module. If so, the module
 	  will be called max1111.
 
+config SENSORS_MAX127
+	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
+	depends on I2C
+	help
+	  Say y here to support Maxim's MAX127 DAS chips.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called max127.
+
 config SENSORS_MAX16065
 	tristate "Maxim MAX16065 System Manager and compatibles"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 1083bbfac779..01ca5d3fbad4 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
 obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
 obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
 obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
+obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
 obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
 obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
 obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
new file mode 100644
index 000000000000..3df4c225a6a2
--- /dev/null
+++ b/drivers/hwmon/max127.c
@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Hardware monitoring driver for MAX127.
+ *
+ * Copyright (c) 2020 Facebook Inc.
+ */
+
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sysfs.h>
+
+/*
+ * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
+ * Format" for details.
+ */
+#define MAX127_CTRL_START	BIT(7)
+#define MAX127_CTRL_SEL_SHIFT	4
+#define MAX127_CTRL_RNG		BIT(3)
+#define MAX127_CTRL_BIP		BIT(2)
+#define MAX127_CTRL_PD1		BIT(1)
+#define MAX127_CTRL_PD0		BIT(0)
+
+#define MAX127_NUM_CHANNELS	8
+#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
+
+/*
+ * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
+ * and Polarity Selection" for details.
+ */
+#define MAX127_FULL_RANGE	10000	/* 10V */
+#define MAX127_HALF_RANGE	5000	/* 5V */
+
+/*
+ * MAX127 returns 2 bytes at read:
+ *   - the first byte contains data[11:4].
+ *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
+ * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
+ * for details.
+ */
+#define MAX127_DATA_LEN		2
+#define MAX127_DATA_SHIFT	4
+
+#define MAX127_SIGN_BIT		BIT(11)
+
+struct max127_data {
+	struct mutex lock;
+	struct i2c_client *client;
+	u8 ctrl_byte[MAX127_NUM_CHANNELS];
+};
+
+static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
+{
+	int status;
+	struct i2c_msg msg = {
+		.addr = client->addr,
+		.flags = 0,
+		.len = sizeof(ctrl_byte),
+		.buf = &ctrl_byte,
+	};
+
+	status = i2c_transfer(client->adapter, &msg, 1);
+	if (status < 0)
+		return status;
+	else if (status != 1)
+		return -EIO;
+
+	return 0;
+}
+
+static int max127_read_channel(struct i2c_client *client, long *val)
+{
+	int status;
+	u8 i2c_data[MAX127_DATA_LEN];
+	struct i2c_msg msg = {
+		.addr = client->addr,
+		.flags = I2C_M_RD,
+		.len = sizeof(i2c_data),
+		.buf = i2c_data,
+	};
+
+	status = i2c_transfer(client->adapter, &msg, 1);
+	if (status < 0)
+		return status;
+	else if (status != 1)
+		return -EIO;
+
+	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
+		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
+	return 0;
+}
+
+static long max127_process_raw(u8 ctrl_byte, long raw)
+{
+	long scale, weight;
+
+	/*
+	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
+	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
+	 * with 1 LSB = [(2 x |FS|)/4096].
+	 * Refer to MAX127 datasheet, "Transfer Function" section for
+	 * details.
+	 */
+	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
+						MAX127_HALF_RANGE;
+	if (ctrl_byte & MAX127_CTRL_BIP) {
+		weight = (raw & MAX127_SIGN_BIT);
+		raw &= ~MAX127_SIGN_BIT;
+		raw -= weight;
+		raw *= 2;
+	}
+
+	return raw * scale / 4096;
+}
+
+static int max127_read_input(struct max127_data *data, int channel, long *val)
+{
+	long raw;
+	int status;
+	struct i2c_client *client = data->client;
+	u8 ctrl_byte = data->ctrl_byte[channel];
+
+	mutex_lock(&data->lock);
+
+	status = max127_select_channel(client, ctrl_byte);
+	if (status)
+		goto exit;
+
+	status = max127_read_channel(client, &raw);
+	if (status)
+		goto exit;
+
+	*val = max127_process_raw(ctrl_byte, raw);
+
+exit:
+	mutex_unlock(&data->lock);
+	return status;
+}
+
+static int max127_read_min(struct max127_data *data, int channel, long *val)
+{
+	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
+	static const int min_input_map[4] = {
+		0,			/* RNG=0, BIP=0 */
+		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
+		0,			/* RNG=1, BIP=0 */
+		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
+	};
+
+	*val = min_input_map[rng_bip];
+	return 0;
+}
+
+static int max127_read_max(struct max127_data *data, int channel, long *val)
+{
+	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
+	static const int max_input_map[4] = {
+		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
+		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
+		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
+		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
+	};
+
+	*val = max_input_map[rng_bip];
+	return 0;
+}
+
+static int max127_write_min(struct max127_data *data, int channel, long val)
+{
+	u8 ctrl;
+
+	ctrl = data->ctrl_byte[channel];
+	if (val <= -MAX127_FULL_RANGE) {
+		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
+	} else if (val < 0) {
+		ctrl |= MAX127_CTRL_BIP;
+		ctrl &= ~MAX127_CTRL_RNG;
+	} else {
+		ctrl &= ~MAX127_CTRL_BIP;
+	}
+	data->ctrl_byte[channel] = ctrl;
+
+	return 0;
+}
+
+static int max127_write_max(struct max127_data *data, int channel, long val)
+{
+	if (val >= MAX127_FULL_RANGE)
+		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
+	else
+		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
+
+	return 0;
+}
+
+static umode_t max127_is_visible(const void *_data,
+				 enum hwmon_sensor_types type,
+				 u32 attr, int channel)
+{
+	if (type == hwmon_in) {
+		switch (attr) {
+		case hwmon_in_input:
+			return 0444;
+
+		case hwmon_in_min:
+		case hwmon_in_max:
+			return 0644;
+
+		default:
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static int max127_read(struct device *dev, enum hwmon_sensor_types type,
+			u32 attr, int channel, long *val)
+{
+	int status;
+	struct max127_data *data = dev_get_drvdata(dev);
+
+	if (type != hwmon_in)
+		return -EOPNOTSUPP;
+
+	switch (attr) {
+	case hwmon_in_input:
+		status = max127_read_input(data, channel, val);
+		break;
+
+	case hwmon_in_min:
+		status = max127_read_min(data, channel, val);
+		break;
+
+	case hwmon_in_max:
+		status = max127_read_max(data, channel, val);
+		break;
+
+	default:
+		status = -EOPNOTSUPP;
+		break;
+	}
+
+	return status;
+}
+
+static int max127_write(struct device *dev, enum hwmon_sensor_types type,
+			u32 attr, int channel, long val)
+{
+	int status;
+	struct max127_data *data = dev_get_drvdata(dev);
+
+	if (type != hwmon_in)
+		return -EOPNOTSUPP;
+
+	switch (attr) {
+	case hwmon_in_min:
+		status = max127_write_min(data, channel, val);
+		break;
+
+	case hwmon_in_max:
+		status = max127_write_max(data, channel, val);
+		break;
+
+	default:
+		status = -EOPNOTSUPP;
+		break;
+	}
+
+	return status;
+}
+
+static const struct hwmon_ops max127_hwmon_ops = {
+	.is_visible = max127_is_visible,
+	.read = max127_read,
+	.write = max127_write,
+};
+
+static const struct hwmon_channel_info *max127_info[] = {
+	HWMON_CHANNEL_INFO(in,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
+	NULL,
+};
+
+static const struct hwmon_chip_info max127_chip_info = {
+	.ops = &max127_hwmon_ops,
+	.info = max127_info,
+};
+
+static int max127_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	int i;
+	struct device *hwmon_dev;
+	struct max127_data *data;
+	struct device *dev = &client->dev;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+	mutex_init(&data->lock);
+	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
+		data->ctrl_byte[i] = (MAX127_CTRL_START |
+				      MAX127_SET_CHANNEL(i));
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
+							 data,
+							 &max127_chip_info,
+							 NULL);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id max127_id[] = {
+	{ "max127", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max127_id);
+
+static struct i2c_driver max127_driver = {
+	.class		= I2C_CLASS_HWMON,
+	.driver = {
+		.name	= "max127",
+	},
+	.probe		= max127_probe,
+	.id_table	= max127_id,
+};
+
+module_i2c_driver(max127_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
+MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
+MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
-- 
2.17.1

[PATCH v3 2/2] docs: hwmon: Document max127 driver

[rentao.bupt]

From: Tao Ren <rentao.bupt@gmail.com>

Add documentation for the max127 hardware monitoring driver.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
---
 Changes in v3:
   - no code change. xdp maintainers were removed from to/cc list.
 Changes in v2:
   - add more description for min/max sysfs nodes.
   - convert values from volt to millivolt in the document.

 Documentation/hwmon/index.rst  |  1 +
 Documentation/hwmon/max127.rst | 45 ++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 Documentation/hwmon/max127.rst

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 408760d13813..0a07b6000c20 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -111,6 +111,7 @@ Hardware Monitoring Kernel Drivers
    ltc4245
    ltc4260
    ltc4261
+   max127
    max16064
    max16065
    max1619
diff --git a/Documentation/hwmon/max127.rst b/Documentation/hwmon/max127.rst
new file mode 100644
index 000000000000..dc192dd9c37c
--- /dev/null
+++ b/Documentation/hwmon/max127.rst
@@ -0,0 +1,45 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver max127
+====================
+
+Author:
+
+  * Tao Ren <rentao.bupt@gmail.com>
+
+Supported chips:
+
+  * Maxim MAX127
+
+    Prefix: 'max127'
+
+    Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX127-MAX128.pdf
+
+Description
+-----------
+
+The MAX127 is a multirange, 12-bit data acquisition system (DAS) providing
+8 analog input channels that are independently software programmable for
+a variety of ranges. The available ranges are {0,5V}, {0,10V}, {-5,5V}
+and {-10,10V}.
+
+The MAX127 features a 2-wire, I2C-compatible serial interface that allows
+communication among multiple devices using SDA and SCL lines.
+
+Sysfs interface
+---------------
+
+  ============== ==============================================================
+  in[0-7]_input  The input voltage (in mV) of the corresponding channel.
+		 RO
+
+  in[0-7]_min    The lower input limit (in mV) for the corresponding channel.
+		 ADC range and LSB will be updated when the limit is changed.
+		 For the MAX127, it will be adjusted to -10000, -5000, or 0.
+		 RW
+
+  in[0-7]_max    The higher input limit (in mV) for the corresponding channel.
+		 ADC range and LSB will be updated when the limit is changed.
+		 For the MAX127, it will be adjusted to 0, 5000, or 10000.
+		 RW
+  ============== ==============================================================
-- 
2.17.1

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Guenter Roeck]

On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> From: Tao Ren <rentao.bupt@gmail.com>
> 
> Add hardware monitoring driver for the Maxim MAX127 chip.
> 
> MAX127 min/max range handling code is inspired by the max197 driver.
> 
> Signed-off-by: Tao Ren <rentao.bupt@gmail.com>

Nice cleanup. Couple of minor comments.

Thanks,
Guenter

> ---
>  Changes in v3:
>    - no code change. xdp maintainers were removed from to/cc list.
>  Changes in v2:
>    - replace devm_hwmon_device_register_with_groups() with
>      devm_hwmon_device_register_with_info() API.
>    - divide min/max read and write methods to separate functions.
>    - fix raw-to-vin conversion logic.
>    - refine ctrl_byte handling so mutex is not needed to protect the
>      byte.
>    - improve i2c_transfer() error handling.
>    - a few other improvements (comments, variable naming, and etc.).
> 
>  drivers/hwmon/Kconfig  |   9 ++
>  drivers/hwmon/Makefile |   1 +
>  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 356 insertions(+)
>  create mode 100644 drivers/hwmon/max127.c
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 9d600e0c5584..716df51edc87 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -950,6 +950,15 @@ config SENSORS_MAX1111
>  	  This driver can also be built as a module. If so, the module
>  	  will be called max1111.
>  
> +config SENSORS_MAX127
> +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> +	depends on I2C
> +	help
> +	  Say y here to support Maxim's MAX127 DAS chips.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called max127.
> +
>  config SENSORS_MAX16065
>  	tristate "Maxim MAX16065 System Manager and compatibles"
>  	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 1083bbfac779..01ca5d3fbad4 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
>  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
>  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
>  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
>  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
>  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
>  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> new file mode 100644
> index 000000000000..3df4c225a6a2
> --- /dev/null
> +++ b/drivers/hwmon/max127.c
> @@ -0,0 +1,346 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Hardware monitoring driver for MAX127.
> + *
> + * Copyright (c) 2020 Facebook Inc.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>

Not needed.

> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/sysfs.h>

Not needed.

> +
> +/*
> + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> + * Format" for details.
> + */
> +#define MAX127_CTRL_START	BIT(7)
> +#define MAX127_CTRL_SEL_SHIFT	4
> +#define MAX127_CTRL_RNG		BIT(3)
> +#define MAX127_CTRL_BIP		BIT(2)
> +#define MAX127_CTRL_PD1		BIT(1)
> +#define MAX127_CTRL_PD0		BIT(0)
> +
> +#define MAX127_NUM_CHANNELS	8
> +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> +
> +/*
> + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> + * and Polarity Selection" for details.
> + */
> +#define MAX127_FULL_RANGE	10000	/* 10V */
> +#define MAX127_HALF_RANGE	5000	/* 5V */
> +
> +/*
> + * MAX127 returns 2 bytes at read:
> + *   - the first byte contains data[11:4].
> + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> + * for details.
> + */
> +#define MAX127_DATA_LEN		2
> +#define MAX127_DATA_SHIFT	4
> +
> +#define MAX127_SIGN_BIT		BIT(11)
> +
> +struct max127_data {
> +	struct mutex lock;
> +	struct i2c_client *client;
> +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> +};
> +
> +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> +{
> +	int status;
> +	struct i2c_msg msg = {
> +		.addr = client->addr,
> +		.flags = 0,
> +		.len = sizeof(ctrl_byte),
> +		.buf = &ctrl_byte,
> +	};
> +
> +	status = i2c_transfer(client->adapter, &msg, 1);
> +	if (status < 0)
> +		return status;
> +	else if (status != 1)

else after return is not needed.

> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int max127_read_channel(struct i2c_client *client, long *val)
> +{
> +	int status;
> +	u8 i2c_data[MAX127_DATA_LEN];
> +	struct i2c_msg msg = {
> +		.addr = client->addr,
> +		.flags = I2C_M_RD,
> +		.len = sizeof(i2c_data),
> +		.buf = i2c_data,
> +	};
> +
> +	status = i2c_transfer(client->adapter, &msg, 1);
> +	if (status < 0)
> +		return status;
> +	else if (status != 1)

else after return is not needed.

> +		return -EIO;
> +
> +	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> +		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> +	return 0;
> +}
> +
> +static long max127_process_raw(u8 ctrl_byte, long raw)
> +{
> +	long scale, weight;
> +
> +	/*
> +	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
> +	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
> +	 * with 1 LSB = [(2 x |FS|)/4096].
> +	 * Refer to MAX127 datasheet, "Transfer Function" section for
> +	 * details.
> +	 */
> +	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> +						MAX127_HALF_RANGE;
> +	if (ctrl_byte & MAX127_CTRL_BIP) {
> +		weight = (raw & MAX127_SIGN_BIT);
> +		raw &= ~MAX127_SIGN_BIT;
> +		raw -= weight;
> +		raw *= 2;
> +	}
> +
> +	return raw * scale / 4096;
> +}
> +
> +static int max127_read_input(struct max127_data *data, int channel, long *val)
> +{
> +	long raw;
> +	int status;
> +	struct i2c_client *client = data->client;
> +	u8 ctrl_byte = data->ctrl_byte[channel];
> +
> +	mutex_lock(&data->lock);
> +
> +	status = max127_select_channel(client, ctrl_byte);
> +	if (status)
> +		goto exit;
> +
> +	status = max127_read_channel(client, &raw);
> +	if (status)
> +		goto exit;
> +
> +	*val = max127_process_raw(ctrl_byte, raw);
> +
> +exit:
> +	mutex_unlock(&data->lock);
> +	return status;
> +}
> +
> +static int max127_read_min(struct max127_data *data, int channel, long *val)
> +{
> +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> +	static const int min_input_map[4] = {
> +		0,			/* RNG=0, BIP=0 */
> +		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> +		0,			/* RNG=1, BIP=0 */
> +		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> +	};
> +
> +	*val = min_input_map[rng_bip];
> +	return 0;
> +}
> +
> +static int max127_read_max(struct max127_data *data, int channel, long *val)
> +{
> +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> +	static const int max_input_map[4] = {
> +		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
> +		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> +		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
> +		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> +	};
> +
> +	*val = max_input_map[rng_bip];
> +	return 0;
> +}
> +
> +static int max127_write_min(struct max127_data *data, int channel, long val)
> +{
> +	u8 ctrl;
> +
> +	ctrl = data->ctrl_byte[channel];
> +	if (val <= -MAX127_FULL_RANGE) {
> +		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> +	} else if (val < 0) {
> +		ctrl |= MAX127_CTRL_BIP;
> +		ctrl &= ~MAX127_CTRL_RNG;
> +	} else {
> +		ctrl &= ~MAX127_CTRL_BIP;
> +	}
> +	data->ctrl_byte[channel] = ctrl;

Needs mutex protection to avoid parallel writes (which might mess up
ctrl_byte[channel]).

> +
> +	return 0;
> +}
> +
> +static int max127_write_max(struct max127_data *data, int channel, long val)
> +{
> +	if (val >= MAX127_FULL_RANGE)
> +		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> +	else
> +		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> +
Same here, to avoid interaction with write_min (which might otherwise
read ctrl and modify it at the same time as this function).

> +	return 0;
> +}
> +
> +static umode_t max127_is_visible(const void *_data,
> +				 enum hwmon_sensor_types type,
> +				 u32 attr, int channel)
> +{
> +	if (type == hwmon_in) {
> +		switch (attr) {
> +		case hwmon_in_input:
> +			return 0444;
> +
> +		case hwmon_in_min:
> +		case hwmon_in_max:
> +			return 0644;
> +
> +		default:
> +			break;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long *val)
> +{
> +	int status;
> +	struct max127_data *data = dev_get_drvdata(dev);
> +
> +	if (type != hwmon_in)
> +		return -EOPNOTSUPP;
> +
> +	switch (attr) {
> +	case hwmon_in_input:
> +		status = max127_read_input(data, channel, val);
> +		break;
> +
> +	case hwmon_in_min:
> +		status = max127_read_min(data, channel, val);
> +		break;
> +
> +	case hwmon_in_max:
> +		status = max127_read_max(data, channel, val);
> +		break;
> +
> +	default:
> +		status = -EOPNOTSUPP;
> +		break;
> +	}
> +
> +	return status;
> +}
> +
> +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long val)
> +{
> +	int status;
> +	struct max127_data *data = dev_get_drvdata(dev);
> +
> +	if (type != hwmon_in)
> +		return -EOPNOTSUPP;
> +
> +	switch (attr) {
> +	case hwmon_in_min:
> +		status = max127_write_min(data, channel, val);
> +		break;
> +
> +	case hwmon_in_max:
> +		status = max127_write_max(data, channel, val);
> +		break;
> +
> +	default:
> +		status = -EOPNOTSUPP;
> +		break;
> +	}
> +
> +	return status;
> +}
> +
> +static const struct hwmon_ops max127_hwmon_ops = {
> +	.is_visible = max127_is_visible,
> +	.read = max127_read,
> +	.write = max127_write,
> +};
> +
> +static const struct hwmon_channel_info *max127_info[] = {
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> +	NULL,
> +};
> +
> +static const struct hwmon_chip_info max127_chip_info = {
> +	.ops = &max127_hwmon_ops,
> +	.info = max127_info,
> +};
> +
> +static int max127_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	int i;
> +	struct device *hwmon_dev;
> +	struct max127_data *data;
> +	struct device *dev = &client->dev;
> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->client = client;
> +	mutex_init(&data->lock);
> +	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> +		data->ctrl_byte[i] = (MAX127_CTRL_START |
> +				      MAX127_SET_CHANNEL(i));
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> +							 data,
> +							 &max127_chip_info,
> +							 NULL);
> +
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct i2c_device_id max127_id[] = {
> +	{ "max127", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, max127_id);
> +
> +static struct i2c_driver max127_driver = {
> +	.class		= I2C_CLASS_HWMON,
> +	.driver = {
> +		.name	= "max127",
> +	},
> +	.probe		= max127_probe,
> +	.id_table	= max127_id,
> +};
> +
> +module_i2c_driver(max127_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
> +MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
> +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Guenter Roeck]

On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> From: Tao Ren <rentao.bupt@gmail.com>
> 
> Add hardware monitoring driver for the Maxim MAX127 chip.
> 
> MAX127 min/max range handling code is inspired by the max197 driver.
> 
> Signed-off-by: Tao Ren <rentao.bupt@gmail.com>

Nice cleanup. Couple of minor comments.

Thanks,
Guenter

> ---
>  Changes in v3:
>    - no code change. xdp maintainers were removed from to/cc list.
>  Changes in v2:
>    - replace devm_hwmon_device_register_with_groups() with
>      devm_hwmon_device_register_with_info() API.
>    - divide min/max read and write methods to separate functions.
>    - fix raw-to-vin conversion logic.
>    - refine ctrl_byte handling so mutex is not needed to protect the
>      byte.
>    - improve i2c_transfer() error handling.
>    - a few other improvements (comments, variable naming, and etc.).
> 
>  drivers/hwmon/Kconfig  |   9 ++
>  drivers/hwmon/Makefile |   1 +
>  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 356 insertions(+)
>  create mode 100644 drivers/hwmon/max127.c
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 9d600e0c5584..716df51edc87 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -950,6 +950,15 @@ config SENSORS_MAX1111
>  	  This driver can also be built as a module. If so, the module
>  	  will be called max1111.
>  
> +config SENSORS_MAX127
> +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> +	depends on I2C
> +	help
> +	  Say y here to support Maxim's MAX127 DAS chips.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called max127.
> +
>  config SENSORS_MAX16065
>  	tristate "Maxim MAX16065 System Manager and compatibles"
>  	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 1083bbfac779..01ca5d3fbad4 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
>  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
>  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
>  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
>  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
>  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
>  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> new file mode 100644
> index 000000000000..3df4c225a6a2
> --- /dev/null
> +++ b/drivers/hwmon/max127.c
> @@ -0,0 +1,346 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Hardware monitoring driver for MAX127.
> + *
> + * Copyright (c) 2020 Facebook Inc.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>

Not needed.

> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/sysfs.h>

Not needed.

> +
> +/*
> + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> + * Format" for details.
> + */
> +#define MAX127_CTRL_START	BIT(7)
> +#define MAX127_CTRL_SEL_SHIFT	4
> +#define MAX127_CTRL_RNG		BIT(3)
> +#define MAX127_CTRL_BIP		BIT(2)
> +#define MAX127_CTRL_PD1		BIT(1)
> +#define MAX127_CTRL_PD0		BIT(0)
> +
> +#define MAX127_NUM_CHANNELS	8
> +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> +
> +/*
> + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> + * and Polarity Selection" for details.
> + */
> +#define MAX127_FULL_RANGE	10000	/* 10V */
> +#define MAX127_HALF_RANGE	5000	/* 5V */
> +
> +/*
> + * MAX127 returns 2 bytes at read:
> + *   - the first byte contains data[11:4].
> + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> + * for details.
> + */
> +#define MAX127_DATA_LEN		2
> +#define MAX127_DATA_SHIFT	4
> +
> +#define MAX127_SIGN_BIT		BIT(11)
> +
> +struct max127_data {
> +	struct mutex lock;
> +	struct i2c_client *client;
> +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> +};
> +
> +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> +{
> +	int status;
> +	struct i2c_msg msg = {
> +		.addr = client->addr,
> +		.flags = 0,
> +		.len = sizeof(ctrl_byte),
> +		.buf = &ctrl_byte,
> +	};
> +
> +	status = i2c_transfer(client->adapter, &msg, 1);
> +	if (status < 0)
> +		return status;
> +	else if (status != 1)

else after return is not needed.

> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int max127_read_channel(struct i2c_client *client, long *val)
> +{
> +	int status;
> +	u8 i2c_data[MAX127_DATA_LEN];
> +	struct i2c_msg msg = {
> +		.addr = client->addr,
> +		.flags = I2C_M_RD,
> +		.len = sizeof(i2c_data),
> +		.buf = i2c_data,
> +	};
> +
> +	status = i2c_transfer(client->adapter, &msg, 1);
> +	if (status < 0)
> +		return status;
> +	else if (status != 1)

else after return is not needed.

> +		return -EIO;
> +
> +	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> +		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> +	return 0;
> +}
> +
> +static long max127_process_raw(u8 ctrl_byte, long raw)
> +{
> +	long scale, weight;
> +
> +	/*
> +	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
> +	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
> +	 * with 1 LSB = [(2 x |FS|)/4096].
> +	 * Refer to MAX127 datasheet, "Transfer Function" section for
> +	 * details.
> +	 */
> +	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> +						MAX127_HALF_RANGE;
> +	if (ctrl_byte & MAX127_CTRL_BIP) {
> +		weight = (raw & MAX127_SIGN_BIT);
> +		raw &= ~MAX127_SIGN_BIT;
> +		raw -= weight;
> +		raw *= 2;
> +	}
> +
> +	return raw * scale / 4096;
> +}
> +
> +static int max127_read_input(struct max127_data *data, int channel, long *val)
> +{
> +	long raw;
> +	int status;
> +	struct i2c_client *client = data->client;
> +	u8 ctrl_byte = data->ctrl_byte[channel];
> +
> +	mutex_lock(&data->lock);
> +
> +	status = max127_select_channel(client, ctrl_byte);
> +	if (status)
> +		goto exit;
> +
> +	status = max127_read_channel(client, &raw);
> +	if (status)
> +		goto exit;
> +
> +	*val = max127_process_raw(ctrl_byte, raw);
> +
> +exit:
> +	mutex_unlock(&data->lock);
> +	return status;
> +}
> +
> +static int max127_read_min(struct max127_data *data, int channel, long *val)
> +{
> +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> +	static const int min_input_map[4] = {
> +		0,			/* RNG=0, BIP=0 */
> +		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> +		0,			/* RNG=1, BIP=0 */
> +		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> +	};
> +
> +	*val = min_input_map[rng_bip];
> +	return 0;
> +}
> +
> +static int max127_read_max(struct max127_data *data, int channel, long *val)
> +{
> +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> +	static const int max_input_map[4] = {
> +		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
> +		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> +		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
> +		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> +	};
> +
> +	*val = max_input_map[rng_bip];
> +	return 0;
> +}
> +
> +static int max127_write_min(struct max127_data *data, int channel, long val)
> +{
> +	u8 ctrl;
> +
> +	ctrl = data->ctrl_byte[channel];
> +	if (val <= -MAX127_FULL_RANGE) {
> +		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> +	} else if (val < 0) {
> +		ctrl |= MAX127_CTRL_BIP;
> +		ctrl &= ~MAX127_CTRL_RNG;
> +	} else {
> +		ctrl &= ~MAX127_CTRL_BIP;
> +	}
> +	data->ctrl_byte[channel] = ctrl;

Needs mutex protection to avoid parallel writes (which might mess up
ctrl_byte[channel]).

> +
> +	return 0;
> +}
> +
> +static int max127_write_max(struct max127_data *data, int channel, long val)
> +{
> +	if (val >= MAX127_FULL_RANGE)
> +		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> +	else
> +		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> +
Same here, to avoid interaction with write_min (which might otherwise
read ctrl and modify it at the same time as this function).

> +	return 0;
> +}
> +
> +static umode_t max127_is_visible(const void *_data,
> +				 enum hwmon_sensor_types type,
> +				 u32 attr, int channel)
> +{
> +	if (type == hwmon_in) {
> +		switch (attr) {
> +		case hwmon_in_input:
> +			return 0444;
> +
> +		case hwmon_in_min:
> +		case hwmon_in_max:
> +			return 0644;
> +
> +		default:
> +			break;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long *val)
> +{
> +	int status;
> +	struct max127_data *data = dev_get_drvdata(dev);
> +
> +	if (type != hwmon_in)
> +		return -EOPNOTSUPP;
> +
> +	switch (attr) {
> +	case hwmon_in_input:
> +		status = max127_read_input(data, channel, val);
> +		break;
> +
> +	case hwmon_in_min:
> +		status = max127_read_min(data, channel, val);
> +		break;
> +
> +	case hwmon_in_max:
> +		status = max127_read_max(data, channel, val);
> +		break;
> +
> +	default:
> +		status = -EOPNOTSUPP;
> +		break;
> +	}
> +
> +	return status;
> +}
> +
> +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long val)
> +{
> +	int status;
> +	struct max127_data *data = dev_get_drvdata(dev);
> +
> +	if (type != hwmon_in)
> +		return -EOPNOTSUPP;
> +
> +	switch (attr) {
> +	case hwmon_in_min:
> +		status = max127_write_min(data, channel, val);
> +		break;
> +
> +	case hwmon_in_max:
> +		status = max127_write_max(data, channel, val);
> +		break;
> +
> +	default:
> +		status = -EOPNOTSUPP;
> +		break;
> +	}
> +
> +	return status;
> +}
> +
> +static const struct hwmon_ops max127_hwmon_ops = {
> +	.is_visible = max127_is_visible,
> +	.read = max127_read,
> +	.write = max127_write,
> +};
> +
> +static const struct hwmon_channel_info *max127_info[] = {
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> +	NULL,
> +};
> +
> +static const struct hwmon_chip_info max127_chip_info = {
> +	.ops = &max127_hwmon_ops,
> +	.info = max127_info,
> +};
> +
> +static int max127_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	int i;
> +	struct device *hwmon_dev;
> +	struct max127_data *data;
> +	struct device *dev = &client->dev;
> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->client = client;
> +	mutex_init(&data->lock);
> +	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> +		data->ctrl_byte[i] = (MAX127_CTRL_START |
> +				      MAX127_SET_CHANNEL(i));
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> +							 data,
> +							 &max127_chip_info,
> +							 NULL);
> +
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct i2c_device_id max127_id[] = {
> +	{ "max127", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, max127_id);
> +
> +static struct i2c_driver max127_driver = {
> +	.class		= I2C_CLASS_HWMON,
> +	.driver = {
> +		.name	= "max127",
> +	},
> +	.probe		= max127_probe,
> +	.id_table	= max127_id,
> +};
> +
> +module_i2c_driver(max127_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
> +MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
> +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");

Re: [PATCH v3 2/2] docs: hwmon: Document max127 driver

[Guenter Roeck]

On Thu, Nov 19, 2020 at 09:53:24AM -0800, rentao.bupt@gmail.com wrote:
> From: Tao Ren <rentao.bupt@gmail.com>
> 
> Add documentation for the max127 hardware monitoring driver.
> 
> Signed-off-by: Tao Ren <rentao.bupt@gmail.com>

For my reference:

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

Guenter

> ---
>  Changes in v3:
>    - no code change. xdp maintainers were removed from to/cc list.
>  Changes in v2:
>    - add more description for min/max sysfs nodes.
>    - convert values from volt to millivolt in the document.
> 
>  Documentation/hwmon/index.rst  |  1 +
>  Documentation/hwmon/max127.rst | 45 ++++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
>  create mode 100644 Documentation/hwmon/max127.rst
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 408760d13813..0a07b6000c20 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -111,6 +111,7 @@ Hardware Monitoring Kernel Drivers
>     ltc4245
>     ltc4260
>     ltc4261
> +   max127
>     max16064
>     max16065
>     max1619
> diff --git a/Documentation/hwmon/max127.rst b/Documentation/hwmon/max127.rst
> new file mode 100644
> index 000000000000..dc192dd9c37c
> --- /dev/null
> +++ b/Documentation/hwmon/max127.rst
> @@ -0,0 +1,45 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +
> +Kernel driver max127
> +====================
> +
> +Author:
> +
> +  * Tao Ren <rentao.bupt@gmail.com>
> +
> +Supported chips:
> +
> +  * Maxim MAX127
> +
> +    Prefix: 'max127'
> +
> +    Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX127-MAX128.pdf
> +
> +Description
> +-----------
> +
> +The MAX127 is a multirange, 12-bit data acquisition system (DAS) providing
> +8 analog input channels that are independently software programmable for
> +a variety of ranges. The available ranges are {0,5V}, {0,10V}, {-5,5V}
> +and {-10,10V}.
> +
> +The MAX127 features a 2-wire, I2C-compatible serial interface that allows
> +communication among multiple devices using SDA and SCL lines.
> +
> +Sysfs interface
> +---------------
> +
> +  ============== ==============================================================
> +  in[0-7]_input  The input voltage (in mV) of the corresponding channel.
> +		 RO
> +
> +  in[0-7]_min    The lower input limit (in mV) for the corresponding channel.
> +		 ADC range and LSB will be updated when the limit is changed.
> +		 For the MAX127, it will be adjusted to -10000, -5000, or 0.
> +		 RW
> +
> +  in[0-7]_max    The higher input limit (in mV) for the corresponding channel.
> +		 ADC range and LSB will be updated when the limit is changed.
> +		 For the MAX127, it will be adjusted to 0, 5000, or 10000.
> +		 RW
> +  ============== ==============================================================

Re: [PATCH v3 2/2] docs: hwmon: Document max127 driver

[Guenter Roeck]

On Thu, Nov 19, 2020 at 09:53:24AM -0800, rentao.bupt@gmail.com wrote:
> From: Tao Ren <rentao.bupt@gmail.com>
> 
> Add documentation for the max127 hardware monitoring driver.
> 
> Signed-off-by: Tao Ren <rentao.bupt@gmail.com>

For my reference:

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

Guenter

> ---
>  Changes in v3:
>    - no code change. xdp maintainers were removed from to/cc list.
>  Changes in v2:
>    - add more description for min/max sysfs nodes.
>    - convert values from volt to millivolt in the document.
> 
>  Documentation/hwmon/index.rst  |  1 +
>  Documentation/hwmon/max127.rst | 45 ++++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
>  create mode 100644 Documentation/hwmon/max127.rst
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 408760d13813..0a07b6000c20 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -111,6 +111,7 @@ Hardware Monitoring Kernel Drivers
>     ltc4245
>     ltc4260
>     ltc4261
> +   max127
>     max16064
>     max16065
>     max1619
> diff --git a/Documentation/hwmon/max127.rst b/Documentation/hwmon/max127.rst
> new file mode 100644
> index 000000000000..dc192dd9c37c
> --- /dev/null
> +++ b/Documentation/hwmon/max127.rst
> @@ -0,0 +1,45 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +
> +Kernel driver max127
> +====================
> +
> +Author:
> +
> +  * Tao Ren <rentao.bupt@gmail.com>
> +
> +Supported chips:
> +
> +  * Maxim MAX127
> +
> +    Prefix: 'max127'
> +
> +    Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX127-MAX128.pdf
> +
> +Description
> +-----------
> +
> +The MAX127 is a multirange, 12-bit data acquisition system (DAS) providing
> +8 analog input channels that are independently software programmable for
> +a variety of ranges. The available ranges are {0,5V}, {0,10V}, {-5,5V}
> +and {-10,10V}.
> +
> +The MAX127 features a 2-wire, I2C-compatible serial interface that allows
> +communication among multiple devices using SDA and SCL lines.
> +
> +Sysfs interface
> +---------------
> +
> +  ============== ==============================================================
> +  in[0-7]_input  The input voltage (in mV) of the corresponding channel.
> +		 RO
> +
> +  in[0-7]_min    The lower input limit (in mV) for the corresponding channel.
> +		 ADC range and LSB will be updated when the limit is changed.
> +		 For the MAX127, it will be adjusted to -10000, -5000, or 0.
> +		 RW
> +
> +  in[0-7]_max    The higher input limit (in mV) for the corresponding channel.
> +		 ADC range and LSB will be updated when the limit is changed.
> +		 For the MAX127, it will be adjusted to 0, 5000, or 10000.
> +		 RW
> +  ============== ==============================================================

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Tao Ren]

On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> > From: Tao Ren <rentao.bupt@gmail.com>
> > 
> > Add hardware monitoring driver for the Maxim MAX127 chip.
> > 
> > MAX127 min/max range handling code is inspired by the max197 driver.
> > 
> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> 
> Nice cleanup. Couple of minor comments.
> 
> Thanks,
> Guenter
> 
> > ---
> >  Changes in v3:
> >    - no code change. xdp maintainers were removed from to/cc list.
> >  Changes in v2:
> >    - replace devm_hwmon_device_register_with_groups() with
> >      devm_hwmon_device_register_with_info() API.
> >    - divide min/max read and write methods to separate functions.
> >    - fix raw-to-vin conversion logic.
> >    - refine ctrl_byte handling so mutex is not needed to protect the
> >      byte.
> >    - improve i2c_transfer() error handling.
> >    - a few other improvements (comments, variable naming, and etc.).
> > 
> >  drivers/hwmon/Kconfig  |   9 ++
> >  drivers/hwmon/Makefile |   1 +
> >  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 356 insertions(+)
> >  create mode 100644 drivers/hwmon/max127.c
> > 
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 9d600e0c5584..716df51edc87 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> >  	  This driver can also be built as a module. If so, the module
> >  	  will be called max1111.
> >  
> > +config SENSORS_MAX127
> > +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > +	depends on I2C
> > +	help
> > +	  Say y here to support Maxim's MAX127 DAS chips.
> > +
> > +	  This driver can also be built as a module. If so, the module
> > +	  will be called max127.
> > +
> >  config SENSORS_MAX16065
> >  	tristate "Maxim MAX16065 System Manager and compatibles"
> >  	depends on I2C
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 1083bbfac779..01ca5d3fbad4 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
> >  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
> >  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> >  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> > +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
> >  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
> >  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
> >  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > new file mode 100644
> > index 000000000000..3df4c225a6a2
> > --- /dev/null
> > +++ b/drivers/hwmon/max127.c
> > @@ -0,0 +1,346 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Hardware monitoring driver for MAX127.
> > + *
> > + * Copyright (c) 2020 Facebook Inc.
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
> 
> Not needed.
> 
> > +#include <linux/i2c.h>
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +#include <linux/sysfs.h>
> 
> Not needed.

Thanks for pointing it out. Both includes are deleted in v4.

> 
> > +
> > +/*
> > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > + * Format" for details.
> > + */
> > +#define MAX127_CTRL_START	BIT(7)
> > +#define MAX127_CTRL_SEL_SHIFT	4
> > +#define MAX127_CTRL_RNG		BIT(3)
> > +#define MAX127_CTRL_BIP		BIT(2)
> > +#define MAX127_CTRL_PD1		BIT(1)
> > +#define MAX127_CTRL_PD0		BIT(0)
> > +
> > +#define MAX127_NUM_CHANNELS	8
> > +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > +
> > +/*
> > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > + * and Polarity Selection" for details.
> > + */
> > +#define MAX127_FULL_RANGE	10000	/* 10V */
> > +#define MAX127_HALF_RANGE	5000	/* 5V */
> > +
> > +/*
> > + * MAX127 returns 2 bytes at read:
> > + *   - the first byte contains data[11:4].
> > + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > + * for details.
> > + */
> > +#define MAX127_DATA_LEN		2
> > +#define MAX127_DATA_SHIFT	4
> > +
> > +#define MAX127_SIGN_BIT		BIT(11)
> > +
> > +struct max127_data {
> > +	struct mutex lock;
> > +	struct i2c_client *client;
> > +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > +};
> > +
> > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > +{
> > +	int status;
> > +	struct i2c_msg msg = {
> > +		.addr = client->addr,
> > +		.flags = 0,
> > +		.len = sizeof(ctrl_byte),
> > +		.buf = &ctrl_byte,
> > +	};
> > +
> > +	status = i2c_transfer(client->adapter, &msg, 1);
> > +	if (status < 0)
> > +		return status;
> > +	else if (status != 1)
> 
> else after return is not needed.
> 
> > +		return -EIO;
> > +
> > +	return 0;
> > +}
> > +
> > +static int max127_read_channel(struct i2c_client *client, long *val)
> > +{
> > +	int status;
> > +	u8 i2c_data[MAX127_DATA_LEN];
> > +	struct i2c_msg msg = {
> > +		.addr = client->addr,
> > +		.flags = I2C_M_RD,
> > +		.len = sizeof(i2c_data),
> > +		.buf = i2c_data,
> > +	};
> > +
> > +	status = i2c_transfer(client->adapter, &msg, 1);
> > +	if (status < 0)
> > +		return status;
> > +	else if (status != 1)
> 
> else after return is not needed.

I'm not sure if I understand your suggestion correctly, and I added this
branch to handle the case when i2c_transfer() returns 0, which means the
message is not transferred. Perhaps it would never happen? but anyhow, I
just simplified the check in v4; please kindly review and let me know if
you have further suggestions.

> 
> > +		return -EIO;
> > +
> > +	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> > +		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> > +	return 0;
> > +}
> > +
> > +static long max127_process_raw(u8 ctrl_byte, long raw)
> > +{
> > +	long scale, weight;
> > +
> > +	/*
> > +	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
> > +	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
> > +	 * with 1 LSB = [(2 x |FS|)/4096].
> > +	 * Refer to MAX127 datasheet, "Transfer Function" section for
> > +	 * details.
> > +	 */
> > +	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> > +						MAX127_HALF_RANGE;
> > +	if (ctrl_byte & MAX127_CTRL_BIP) {
> > +		weight = (raw & MAX127_SIGN_BIT);
> > +		raw &= ~MAX127_SIGN_BIT;
> > +		raw -= weight;
> > +		raw *= 2;
> > +	}
> > +
> > +	return raw * scale / 4096;
> > +}
> > +
> > +static int max127_read_input(struct max127_data *data, int channel, long *val)
> > +{
> > +	long raw;
> > +	int status;
> > +	struct i2c_client *client = data->client;
> > +	u8 ctrl_byte = data->ctrl_byte[channel];
> > +
> > +	mutex_lock(&data->lock);
> > +
> > +	status = max127_select_channel(client, ctrl_byte);
> > +	if (status)
> > +		goto exit;
> > +
> > +	status = max127_read_channel(client, &raw);
> > +	if (status)
> > +		goto exit;
> > +
> > +	*val = max127_process_raw(ctrl_byte, raw);
> > +
> > +exit:
> > +	mutex_unlock(&data->lock);
> > +	return status;
> > +}
> > +
> > +static int max127_read_min(struct max127_data *data, int channel, long *val)
> > +{
> > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > +	static const int min_input_map[4] = {
> > +		0,			/* RNG=0, BIP=0 */
> > +		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > +		0,			/* RNG=1, BIP=0 */
> > +		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > +	};
> > +
> > +	*val = min_input_map[rng_bip];
> > +	return 0;
> > +}
> > +
> > +static int max127_read_max(struct max127_data *data, int channel, long *val)
> > +{
> > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > +	static const int max_input_map[4] = {
> > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
> > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
> > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > +	};
> > +
> > +	*val = max_input_map[rng_bip];
> > +	return 0;
> > +}
> > +
> > +static int max127_write_min(struct max127_data *data, int channel, long val)
> > +{
> > +	u8 ctrl;
> > +
> > +	ctrl = data->ctrl_byte[channel];
> > +	if (val <= -MAX127_FULL_RANGE) {
> > +		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> > +	} else if (val < 0) {
> > +		ctrl |= MAX127_CTRL_BIP;
> > +		ctrl &= ~MAX127_CTRL_RNG;
> > +	} else {
> > +		ctrl &= ~MAX127_CTRL_BIP;
> > +	}
> > +	data->ctrl_byte[channel] = ctrl;
> 
> Needs mutex protection to avoid parallel writes (which might mess up
> ctrl_byte[channel]).
> 
> > +
> > +	return 0;
> > +}
> > +
> > +static int max127_write_max(struct max127_data *data, int channel, long val)
> > +{
> > +	if (val >= MAX127_FULL_RANGE)
> > +		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> > +	else
> > +		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> > +
> Same here, to avoid interaction with write_min (which might otherwise
> read ctrl and modify it at the same time as this function).

Thanks for pointing it out, and both functions are protected by mutex in
v4.


Cheers,

Tao

> 
> > +	return 0;
> > +}
> > +
> > +static umode_t max127_is_visible(const void *_data,
> > +				 enum hwmon_sensor_types type,
> > +				 u32 attr, int channel)
> > +{
> > +	if (type == hwmon_in) {
> > +		switch (attr) {
> > +		case hwmon_in_input:
> > +			return 0444;
> > +
> > +		case hwmon_in_min:
> > +		case hwmon_in_max:
> > +			return 0644;
> > +
> > +		default:
> > +			break;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> > +			u32 attr, int channel, long *val)
> > +{
> > +	int status;
> > +	struct max127_data *data = dev_get_drvdata(dev);
> > +
> > +	if (type != hwmon_in)
> > +		return -EOPNOTSUPP;
> > +
> > +	switch (attr) {
> > +	case hwmon_in_input:
> > +		status = max127_read_input(data, channel, val);
> > +		break;
> > +
> > +	case hwmon_in_min:
> > +		status = max127_read_min(data, channel, val);
> > +		break;
> > +
> > +	case hwmon_in_max:
> > +		status = max127_read_max(data, channel, val);
> > +		break;
> > +
> > +	default:
> > +		status = -EOPNOTSUPP;
> > +		break;
> > +	}
> > +
> > +	return status;
> > +}
> > +
> > +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> > +			u32 attr, int channel, long val)
> > +{
> > +	int status;
> > +	struct max127_data *data = dev_get_drvdata(dev);
> > +
> > +	if (type != hwmon_in)
> > +		return -EOPNOTSUPP;
> > +
> > +	switch (attr) {
> > +	case hwmon_in_min:
> > +		status = max127_write_min(data, channel, val);
> > +		break;
> > +
> > +	case hwmon_in_max:
> > +		status = max127_write_max(data, channel, val);
> > +		break;
> > +
> > +	default:
> > +		status = -EOPNOTSUPP;
> > +		break;
> > +	}
> > +
> > +	return status;
> > +}
> > +
> > +static const struct hwmon_ops max127_hwmon_ops = {
> > +	.is_visible = max127_is_visible,
> > +	.read = max127_read,
> > +	.write = max127_write,
> > +};
> > +
> > +static const struct hwmon_channel_info *max127_info[] = {
> > +	HWMON_CHANNEL_INFO(in,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> > +	NULL,
> > +};
> > +
> > +static const struct hwmon_chip_info max127_chip_info = {
> > +	.ops = &max127_hwmon_ops,
> > +	.info = max127_info,
> > +};
> > +
> > +static int max127_probe(struct i2c_client *client,
> > +			const struct i2c_device_id *id)
> > +{
> > +	int i;
> > +	struct device *hwmon_dev;
> > +	struct max127_data *data;
> > +	struct device *dev = &client->dev;
> > +
> > +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	data->client = client;
> > +	mutex_init(&data->lock);
> > +	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> > +		data->ctrl_byte[i] = (MAX127_CTRL_START |
> > +				      MAX127_SET_CHANNEL(i));
> > +
> > +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> > +							 data,
> > +							 &max127_chip_info,
> > +							 NULL);
> > +
> > +	return PTR_ERR_OR_ZERO(hwmon_dev);
> > +}
> > +
> > +static const struct i2c_device_id max127_id[] = {
> > +	{ "max127", 0 },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, max127_id);
> > +
> > +static struct i2c_driver max127_driver = {
> > +	.class		= I2C_CLASS_HWMON,
> > +	.driver = {
> > +		.name	= "max127",
> > +	},
> > +	.probe		= max127_probe,
> > +	.id_table	= max127_id,
> > +};
> > +
> > +module_i2c_driver(max127_driver);
> > +
> > +MODULE_LICENSE("GPL");
> > +MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
> > +MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
> > +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Tao Ren]

On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> > From: Tao Ren <rentao.bupt@gmail.com>
> > 
> > Add hardware monitoring driver for the Maxim MAX127 chip.
> > 
> > MAX127 min/max range handling code is inspired by the max197 driver.
> > 
> > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> 
> Nice cleanup. Couple of minor comments.
> 
> Thanks,
> Guenter
> 
> > ---
> >  Changes in v3:
> >    - no code change. xdp maintainers were removed from to/cc list.
> >  Changes in v2:
> >    - replace devm_hwmon_device_register_with_groups() with
> >      devm_hwmon_device_register_with_info() API.
> >    - divide min/max read and write methods to separate functions.
> >    - fix raw-to-vin conversion logic.
> >    - refine ctrl_byte handling so mutex is not needed to protect the
> >      byte.
> >    - improve i2c_transfer() error handling.
> >    - a few other improvements (comments, variable naming, and etc.).
> > 
> >  drivers/hwmon/Kconfig  |   9 ++
> >  drivers/hwmon/Makefile |   1 +
> >  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 356 insertions(+)
> >  create mode 100644 drivers/hwmon/max127.c
> > 
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 9d600e0c5584..716df51edc87 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> >  	  This driver can also be built as a module. If so, the module
> >  	  will be called max1111.
> >  
> > +config SENSORS_MAX127
> > +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > +	depends on I2C
> > +	help
> > +	  Say y here to support Maxim's MAX127 DAS chips.
> > +
> > +	  This driver can also be built as a module. If so, the module
> > +	  will be called max127.
> > +
> >  config SENSORS_MAX16065
> >  	tristate "Maxim MAX16065 System Manager and compatibles"
> >  	depends on I2C
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 1083bbfac779..01ca5d3fbad4 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
> >  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
> >  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> >  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> > +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
> >  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
> >  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
> >  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > new file mode 100644
> > index 000000000000..3df4c225a6a2
> > --- /dev/null
> > +++ b/drivers/hwmon/max127.c
> > @@ -0,0 +1,346 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Hardware monitoring driver for MAX127.
> > + *
> > + * Copyright (c) 2020 Facebook Inc.
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
> 
> Not needed.
> 
> > +#include <linux/i2c.h>
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +#include <linux/sysfs.h>
> 
> Not needed.

Thanks for pointing it out. Both includes are deleted in v4.

> 
> > +
> > +/*
> > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > + * Format" for details.
> > + */
> > +#define MAX127_CTRL_START	BIT(7)
> > +#define MAX127_CTRL_SEL_SHIFT	4
> > +#define MAX127_CTRL_RNG		BIT(3)
> > +#define MAX127_CTRL_BIP		BIT(2)
> > +#define MAX127_CTRL_PD1		BIT(1)
> > +#define MAX127_CTRL_PD0		BIT(0)
> > +
> > +#define MAX127_NUM_CHANNELS	8
> > +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > +
> > +/*
> > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > + * and Polarity Selection" for details.
> > + */
> > +#define MAX127_FULL_RANGE	10000	/* 10V */
> > +#define MAX127_HALF_RANGE	5000	/* 5V */
> > +
> > +/*
> > + * MAX127 returns 2 bytes at read:
> > + *   - the first byte contains data[11:4].
> > + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > + * for details.
> > + */
> > +#define MAX127_DATA_LEN		2
> > +#define MAX127_DATA_SHIFT	4
> > +
> > +#define MAX127_SIGN_BIT		BIT(11)
> > +
> > +struct max127_data {
> > +	struct mutex lock;
> > +	struct i2c_client *client;
> > +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > +};
> > +
> > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > +{
> > +	int status;
> > +	struct i2c_msg msg = {
> > +		.addr = client->addr,
> > +		.flags = 0,
> > +		.len = sizeof(ctrl_byte),
> > +		.buf = &ctrl_byte,
> > +	};
> > +
> > +	status = i2c_transfer(client->adapter, &msg, 1);
> > +	if (status < 0)
> > +		return status;
> > +	else if (status != 1)
> 
> else after return is not needed.
> 
> > +		return -EIO;
> > +
> > +	return 0;
> > +}
> > +
> > +static int max127_read_channel(struct i2c_client *client, long *val)
> > +{
> > +	int status;
> > +	u8 i2c_data[MAX127_DATA_LEN];
> > +	struct i2c_msg msg = {
> > +		.addr = client->addr,
> > +		.flags = I2C_M_RD,
> > +		.len = sizeof(i2c_data),
> > +		.buf = i2c_data,
> > +	};
> > +
> > +	status = i2c_transfer(client->adapter, &msg, 1);
> > +	if (status < 0)
> > +		return status;
> > +	else if (status != 1)
> 
> else after return is not needed.

I'm not sure if I understand your suggestion correctly, and I added this
branch to handle the case when i2c_transfer() returns 0, which means the
message is not transferred. Perhaps it would never happen? but anyhow, I
just simplified the check in v4; please kindly review and let me know if
you have further suggestions.

> 
> > +		return -EIO;
> > +
> > +	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> > +		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> > +	return 0;
> > +}
> > +
> > +static long max127_process_raw(u8 ctrl_byte, long raw)
> > +{
> > +	long scale, weight;
> > +
> > +	/*
> > +	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
> > +	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
> > +	 * with 1 LSB = [(2 x |FS|)/4096].
> > +	 * Refer to MAX127 datasheet, "Transfer Function" section for
> > +	 * details.
> > +	 */
> > +	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> > +						MAX127_HALF_RANGE;
> > +	if (ctrl_byte & MAX127_CTRL_BIP) {
> > +		weight = (raw & MAX127_SIGN_BIT);
> > +		raw &= ~MAX127_SIGN_BIT;
> > +		raw -= weight;
> > +		raw *= 2;
> > +	}
> > +
> > +	return raw * scale / 4096;
> > +}
> > +
> > +static int max127_read_input(struct max127_data *data, int channel, long *val)
> > +{
> > +	long raw;
> > +	int status;
> > +	struct i2c_client *client = data->client;
> > +	u8 ctrl_byte = data->ctrl_byte[channel];
> > +
> > +	mutex_lock(&data->lock);
> > +
> > +	status = max127_select_channel(client, ctrl_byte);
> > +	if (status)
> > +		goto exit;
> > +
> > +	status = max127_read_channel(client, &raw);
> > +	if (status)
> > +		goto exit;
> > +
> > +	*val = max127_process_raw(ctrl_byte, raw);
> > +
> > +exit:
> > +	mutex_unlock(&data->lock);
> > +	return status;
> > +}
> > +
> > +static int max127_read_min(struct max127_data *data, int channel, long *val)
> > +{
> > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > +	static const int min_input_map[4] = {
> > +		0,			/* RNG=0, BIP=0 */
> > +		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > +		0,			/* RNG=1, BIP=0 */
> > +		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > +	};
> > +
> > +	*val = min_input_map[rng_bip];
> > +	return 0;
> > +}
> > +
> > +static int max127_read_max(struct max127_data *data, int channel, long *val)
> > +{
> > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > +	static const int max_input_map[4] = {
> > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
> > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
> > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > +	};
> > +
> > +	*val = max_input_map[rng_bip];
> > +	return 0;
> > +}
> > +
> > +static int max127_write_min(struct max127_data *data, int channel, long val)
> > +{
> > +	u8 ctrl;
> > +
> > +	ctrl = data->ctrl_byte[channel];
> > +	if (val <= -MAX127_FULL_RANGE) {
> > +		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> > +	} else if (val < 0) {
> > +		ctrl |= MAX127_CTRL_BIP;
> > +		ctrl &= ~MAX127_CTRL_RNG;
> > +	} else {
> > +		ctrl &= ~MAX127_CTRL_BIP;
> > +	}
> > +	data->ctrl_byte[channel] = ctrl;
> 
> Needs mutex protection to avoid parallel writes (which might mess up
> ctrl_byte[channel]).
> 
> > +
> > +	return 0;
> > +}
> > +
> > +static int max127_write_max(struct max127_data *data, int channel, long val)
> > +{
> > +	if (val >= MAX127_FULL_RANGE)
> > +		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> > +	else
> > +		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> > +
> Same here, to avoid interaction with write_min (which might otherwise
> read ctrl and modify it at the same time as this function).

Thanks for pointing it out, and both functions are protected by mutex in
v4.


Cheers,

Tao

> 
> > +	return 0;
> > +}
> > +
> > +static umode_t max127_is_visible(const void *_data,
> > +				 enum hwmon_sensor_types type,
> > +				 u32 attr, int channel)
> > +{
> > +	if (type == hwmon_in) {
> > +		switch (attr) {
> > +		case hwmon_in_input:
> > +			return 0444;
> > +
> > +		case hwmon_in_min:
> > +		case hwmon_in_max:
> > +			return 0644;
> > +
> > +		default:
> > +			break;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> > +			u32 attr, int channel, long *val)
> > +{
> > +	int status;
> > +	struct max127_data *data = dev_get_drvdata(dev);
> > +
> > +	if (type != hwmon_in)
> > +		return -EOPNOTSUPP;
> > +
> > +	switch (attr) {
> > +	case hwmon_in_input:
> > +		status = max127_read_input(data, channel, val);
> > +		break;
> > +
> > +	case hwmon_in_min:
> > +		status = max127_read_min(data, channel, val);
> > +		break;
> > +
> > +	case hwmon_in_max:
> > +		status = max127_read_max(data, channel, val);
> > +		break;
> > +
> > +	default:
> > +		status = -EOPNOTSUPP;
> > +		break;
> > +	}
> > +
> > +	return status;
> > +}
> > +
> > +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> > +			u32 attr, int channel, long val)
> > +{
> > +	int status;
> > +	struct max127_data *data = dev_get_drvdata(dev);
> > +
> > +	if (type != hwmon_in)
> > +		return -EOPNOTSUPP;
> > +
> > +	switch (attr) {
> > +	case hwmon_in_min:
> > +		status = max127_write_min(data, channel, val);
> > +		break;
> > +
> > +	case hwmon_in_max:
> > +		status = max127_write_max(data, channel, val);
> > +		break;
> > +
> > +	default:
> > +		status = -EOPNOTSUPP;
> > +		break;
> > +	}
> > +
> > +	return status;
> > +}
> > +
> > +static const struct hwmon_ops max127_hwmon_ops = {
> > +	.is_visible = max127_is_visible,
> > +	.read = max127_read,
> > +	.write = max127_write,
> > +};
> > +
> > +static const struct hwmon_channel_info *max127_info[] = {
> > +	HWMON_CHANNEL_INFO(in,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> > +	NULL,
> > +};
> > +
> > +static const struct hwmon_chip_info max127_chip_info = {
> > +	.ops = &max127_hwmon_ops,
> > +	.info = max127_info,
> > +};
> > +
> > +static int max127_probe(struct i2c_client *client,
> > +			const struct i2c_device_id *id)
> > +{
> > +	int i;
> > +	struct device *hwmon_dev;
> > +	struct max127_data *data;
> > +	struct device *dev = &client->dev;
> > +
> > +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	data->client = client;
> > +	mutex_init(&data->lock);
> > +	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> > +		data->ctrl_byte[i] = (MAX127_CTRL_START |
> > +				      MAX127_SET_CHANNEL(i));
> > +
> > +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> > +							 data,
> > +							 &max127_chip_info,
> > +							 NULL);
> > +
> > +	return PTR_ERR_OR_ZERO(hwmon_dev);
> > +}
> > +
> > +static const struct i2c_device_id max127_id[] = {
> > +	{ "max127", 0 },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, max127_id);
> > +
> > +static struct i2c_driver max127_driver = {
> > +	.class		= I2C_CLASS_HWMON,
> > +	.driver = {
> > +		.name	= "max127",
> > +	},
> > +	.probe		= max127_probe,
> > +	.id_table	= max127_id,
> > +};
> > +
> > +module_i2c_driver(max127_driver);
> > +
> > +MODULE_LICENSE("GPL");
> > +MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
> > +MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
> > +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Guenter Roeck]

On Sun, Nov 22, 2020 at 11:54:49PM -0800, Tao Ren wrote:
> On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> > On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> > > From: Tao Ren <rentao.bupt@gmail.com>
> > > 
> > > Add hardware monitoring driver for the Maxim MAX127 chip.
> > > 
> > > MAX127 min/max range handling code is inspired by the max197 driver.
> > > 
> > > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> > 
> > Nice cleanup. Couple of minor comments.
> > 
> > Thanks,
> > Guenter
> > 
> > > ---
> > >  Changes in v3:
> > >    - no code change. xdp maintainers were removed from to/cc list.
> > >  Changes in v2:
> > >    - replace devm_hwmon_device_register_with_groups() with
> > >      devm_hwmon_device_register_with_info() API.
> > >    - divide min/max read and write methods to separate functions.
> > >    - fix raw-to-vin conversion logic.
> > >    - refine ctrl_byte handling so mutex is not needed to protect the
> > >      byte.
> > >    - improve i2c_transfer() error handling.
> > >    - a few other improvements (comments, variable naming, and etc.).
> > > 
> > >  drivers/hwmon/Kconfig  |   9 ++
> > >  drivers/hwmon/Makefile |   1 +
> > >  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > >  3 files changed, 356 insertions(+)
> > >  create mode 100644 drivers/hwmon/max127.c
> > > 
> > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > index 9d600e0c5584..716df51edc87 100644
> > > --- a/drivers/hwmon/Kconfig
> > > +++ b/drivers/hwmon/Kconfig
> > > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > >  	  This driver can also be built as a module. If so, the module
> > >  	  will be called max1111.
> > >  
> > > +config SENSORS_MAX127
> > > +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > > +	depends on I2C
> > > +	help
> > > +	  Say y here to support Maxim's MAX127 DAS chips.
> > > +
> > > +	  This driver can also be built as a module. If so, the module
> > > +	  will be called max127.
> > > +
> > >  config SENSORS_MAX16065
> > >  	tristate "Maxim MAX16065 System Manager and compatibles"
> > >  	depends on I2C
> > > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > > index 1083bbfac779..01ca5d3fbad4 100644
> > > --- a/drivers/hwmon/Makefile
> > > +++ b/drivers/hwmon/Makefile
> > > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
> > >  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
> > >  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > >  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> > > +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
> > >  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
> > >  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
> > >  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> > > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > > new file mode 100644
> > > index 000000000000..3df4c225a6a2
> > > --- /dev/null
> > > +++ b/drivers/hwmon/max127.c
> > > @@ -0,0 +1,346 @@
> > > +// SPDX-License-Identifier: GPL-2.0+
> > > +/*
> > > + * Hardware monitoring driver for MAX127.
> > > + *
> > > + * Copyright (c) 2020 Facebook Inc.
> > > + */
> > > +
> > > +#include <linux/err.h>
> > > +#include <linux/hwmon.h>
> > > +#include <linux/hwmon-sysfs.h>
> > 
> > Not needed.
> > 
> > > +#include <linux/i2c.h>
> > > +#include <linux/init.h>
> > > +#include <linux/module.h>
> > > +#include <linux/sysfs.h>
> > 
> > Not needed.
> 
> Thanks for pointing it out. Both includes are deleted in v4.
> 
> > 
> > > +
> > > +/*
> > > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > > + * Format" for details.
> > > + */
> > > +#define MAX127_CTRL_START	BIT(7)
> > > +#define MAX127_CTRL_SEL_SHIFT	4
> > > +#define MAX127_CTRL_RNG		BIT(3)
> > > +#define MAX127_CTRL_BIP		BIT(2)
> > > +#define MAX127_CTRL_PD1		BIT(1)
> > > +#define MAX127_CTRL_PD0		BIT(0)
> > > +
> > > +#define MAX127_NUM_CHANNELS	8
> > > +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > > +
> > > +/*
> > > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > > + * and Polarity Selection" for details.
> > > + */
> > > +#define MAX127_FULL_RANGE	10000	/* 10V */
> > > +#define MAX127_HALF_RANGE	5000	/* 5V */
> > > +
> > > +/*
> > > + * MAX127 returns 2 bytes at read:
> > > + *   - the first byte contains data[11:4].
> > > + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > > + * for details.
> > > + */
> > > +#define MAX127_DATA_LEN		2
> > > +#define MAX127_DATA_SHIFT	4
> > > +
> > > +#define MAX127_SIGN_BIT		BIT(11)
> > > +
> > > +struct max127_data {
> > > +	struct mutex lock;
> > > +	struct i2c_client *client;
> > > +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > > +};
> > > +
> > > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > > +{
> > > +	int status;
> > > +	struct i2c_msg msg = {
> > > +		.addr = client->addr,
> > > +		.flags = 0,
> > > +		.len = sizeof(ctrl_byte),
> > > +		.buf = &ctrl_byte,
> > > +	};
> > > +
> > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > +	if (status < 0)
> > > +		return status;
> > > +	else if (status != 1)
> > 
> > else after return is not needed.
> > 
> > > +		return -EIO;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_read_channel(struct i2c_client *client, long *val)
> > > +{
> > > +	int status;
> > > +	u8 i2c_data[MAX127_DATA_LEN];
> > > +	struct i2c_msg msg = {
> > > +		.addr = client->addr,
> > > +		.flags = I2C_M_RD,
> > > +		.len = sizeof(i2c_data),
> > > +		.buf = i2c_data,
> > > +	};
> > > +
> > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > +	if (status < 0)
> > > +		return status;
> > > +	else if (status != 1)
> > 
> > else after return is not needed.
> 
> I'm not sure if I understand your suggestion correctly, and I added this
> branch to handle the case when i2c_transfer() returns 0, which means the
> message is not transferred. Perhaps it would never happen? but anyhow, I
> just simplified the check in v4; please kindly review and let me know if
> you have further suggestions.
> 

	if (status < 0)
		return status;
	if (status != 1)
		return -EIO;

Again, else after return is not needed (and static analyzers will complain
about it).

Guenter

> > 
> > > +		return -EIO;
> > > +
> > > +	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> > > +		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> > > +	return 0;
> > > +}
> > > +
> > > +static long max127_process_raw(u8 ctrl_byte, long raw)
> > > +{
> > > +	long scale, weight;
> > > +
> > > +	/*
> > > +	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
> > > +	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
> > > +	 * with 1 LSB = [(2 x |FS|)/4096].
> > > +	 * Refer to MAX127 datasheet, "Transfer Function" section for
> > > +	 * details.
> > > +	 */
> > > +	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> > > +						MAX127_HALF_RANGE;
> > > +	if (ctrl_byte & MAX127_CTRL_BIP) {
> > > +		weight = (raw & MAX127_SIGN_BIT);
> > > +		raw &= ~MAX127_SIGN_BIT;
> > > +		raw -= weight;
> > > +		raw *= 2;
> > > +	}
> > > +
> > > +	return raw * scale / 4096;
> > > +}
> > > +
> > > +static int max127_read_input(struct max127_data *data, int channel, long *val)
> > > +{
> > > +	long raw;
> > > +	int status;
> > > +	struct i2c_client *client = data->client;
> > > +	u8 ctrl_byte = data->ctrl_byte[channel];
> > > +
> > > +	mutex_lock(&data->lock);
> > > +
> > > +	status = max127_select_channel(client, ctrl_byte);
> > > +	if (status)
> > > +		goto exit;
> > > +
> > > +	status = max127_read_channel(client, &raw);
> > > +	if (status)
> > > +		goto exit;
> > > +
> > > +	*val = max127_process_raw(ctrl_byte, raw);
> > > +
> > > +exit:
> > > +	mutex_unlock(&data->lock);
> > > +	return status;
> > > +}
> > > +
> > > +static int max127_read_min(struct max127_data *data, int channel, long *val)
> > > +{
> > > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > > +	static const int min_input_map[4] = {
> > > +		0,			/* RNG=0, BIP=0 */
> > > +		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > > +		0,			/* RNG=1, BIP=0 */
> > > +		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > > +	};
> > > +
> > > +	*val = min_input_map[rng_bip];
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_read_max(struct max127_data *data, int channel, long *val)
> > > +{
> > > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > > +	static const int max_input_map[4] = {
> > > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
> > > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
> > > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > > +	};
> > > +
> > > +	*val = max_input_map[rng_bip];
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_write_min(struct max127_data *data, int channel, long val)
> > > +{
> > > +	u8 ctrl;
> > > +
> > > +	ctrl = data->ctrl_byte[channel];
> > > +	if (val <= -MAX127_FULL_RANGE) {
> > > +		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> > > +	} else if (val < 0) {
> > > +		ctrl |= MAX127_CTRL_BIP;
> > > +		ctrl &= ~MAX127_CTRL_RNG;
> > > +	} else {
> > > +		ctrl &= ~MAX127_CTRL_BIP;
> > > +	}
> > > +	data->ctrl_byte[channel] = ctrl;
> > 
> > Needs mutex protection to avoid parallel writes (which might mess up
> > ctrl_byte[channel]).
> > 
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_write_max(struct max127_data *data, int channel, long val)
> > > +{
> > > +	if (val >= MAX127_FULL_RANGE)
> > > +		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> > > +	else
> > > +		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> > > +
> > Same here, to avoid interaction with write_min (which might otherwise
> > read ctrl and modify it at the same time as this function).
> 
> Thanks for pointing it out, and both functions are protected by mutex in
> v4.
> 
> 
> Cheers,
> 
> Tao
> 
> > 
> > > +	return 0;
> > > +}
> > > +
> > > +static umode_t max127_is_visible(const void *_data,
> > > +				 enum hwmon_sensor_types type,
> > > +				 u32 attr, int channel)
> > > +{
> > > +	if (type == hwmon_in) {
> > > +		switch (attr) {
> > > +		case hwmon_in_input:
> > > +			return 0444;
> > > +
> > > +		case hwmon_in_min:
> > > +		case hwmon_in_max:
> > > +			return 0644;
> > > +
> > > +		default:
> > > +			break;
> > > +		}
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> > > +			u32 attr, int channel, long *val)
> > > +{
> > > +	int status;
> > > +	struct max127_data *data = dev_get_drvdata(dev);
> > > +
> > > +	if (type != hwmon_in)
> > > +		return -EOPNOTSUPP;
> > > +
> > > +	switch (attr) {
> > > +	case hwmon_in_input:
> > > +		status = max127_read_input(data, channel, val);
> > > +		break;
> > > +
> > > +	case hwmon_in_min:
> > > +		status = max127_read_min(data, channel, val);
> > > +		break;
> > > +
> > > +	case hwmon_in_max:
> > > +		status = max127_read_max(data, channel, val);
> > > +		break;
> > > +
> > > +	default:
> > > +		status = -EOPNOTSUPP;
> > > +		break;
> > > +	}
> > > +
> > > +	return status;
> > > +}
> > > +
> > > +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> > > +			u32 attr, int channel, long val)
> > > +{
> > > +	int status;
> > > +	struct max127_data *data = dev_get_drvdata(dev);
> > > +
> > > +	if (type != hwmon_in)
> > > +		return -EOPNOTSUPP;
> > > +
> > > +	switch (attr) {
> > > +	case hwmon_in_min:
> > > +		status = max127_write_min(data, channel, val);
> > > +		break;
> > > +
> > > +	case hwmon_in_max:
> > > +		status = max127_write_max(data, channel, val);
> > > +		break;
> > > +
> > > +	default:
> > > +		status = -EOPNOTSUPP;
> > > +		break;
> > > +	}
> > > +
> > > +	return status;
> > > +}
> > > +
> > > +static const struct hwmon_ops max127_hwmon_ops = {
> > > +	.is_visible = max127_is_visible,
> > > +	.read = max127_read,
> > > +	.write = max127_write,
> > > +};
> > > +
> > > +static const struct hwmon_channel_info *max127_info[] = {
> > > +	HWMON_CHANNEL_INFO(in,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> > > +	NULL,
> > > +};
> > > +
> > > +static const struct hwmon_chip_info max127_chip_info = {
> > > +	.ops = &max127_hwmon_ops,
> > > +	.info = max127_info,
> > > +};
> > > +
> > > +static int max127_probe(struct i2c_client *client,
> > > +			const struct i2c_device_id *id)
> > > +{
> > > +	int i;
> > > +	struct device *hwmon_dev;
> > > +	struct max127_data *data;
> > > +	struct device *dev = &client->dev;
> > > +
> > > +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > > +	if (!data)
> > > +		return -ENOMEM;
> > > +
> > > +	data->client = client;
> > > +	mutex_init(&data->lock);
> > > +	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> > > +		data->ctrl_byte[i] = (MAX127_CTRL_START |
> > > +				      MAX127_SET_CHANNEL(i));
> > > +
> > > +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> > > +							 data,
> > > +							 &max127_chip_info,
> > > +							 NULL);
> > > +
> > > +	return PTR_ERR_OR_ZERO(hwmon_dev);
> > > +}
> > > +
> > > +static const struct i2c_device_id max127_id[] = {
> > > +	{ "max127", 0 },
> > > +	{ }
> > > +};
> > > +MODULE_DEVICE_TABLE(i2c, max127_id);
> > > +
> > > +static struct i2c_driver max127_driver = {
> > > +	.class		= I2C_CLASS_HWMON,
> > > +	.driver = {
> > > +		.name	= "max127",
> > > +	},
> > > +	.probe		= max127_probe,
> > > +	.id_table	= max127_id,
> > > +};
> > > +
> > > +module_i2c_driver(max127_driver);
> > > +
> > > +MODULE_LICENSE("GPL");
> > > +MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
> > > +MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
> > > +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Guenter Roeck]

On Sun, Nov 22, 2020 at 11:54:49PM -0800, Tao Ren wrote:
> On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> > On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> > > From: Tao Ren <rentao.bupt@gmail.com>
> > > 
> > > Add hardware monitoring driver for the Maxim MAX127 chip.
> > > 
> > > MAX127 min/max range handling code is inspired by the max197 driver.
> > > 
> > > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> > 
> > Nice cleanup. Couple of minor comments.
> > 
> > Thanks,
> > Guenter
> > 
> > > ---
> > >  Changes in v3:
> > >    - no code change. xdp maintainers were removed from to/cc list.
> > >  Changes in v2:
> > >    - replace devm_hwmon_device_register_with_groups() with
> > >      devm_hwmon_device_register_with_info() API.
> > >    - divide min/max read and write methods to separate functions.
> > >    - fix raw-to-vin conversion logic.
> > >    - refine ctrl_byte handling so mutex is not needed to protect the
> > >      byte.
> > >    - improve i2c_transfer() error handling.
> > >    - a few other improvements (comments, variable naming, and etc.).
> > > 
> > >  drivers/hwmon/Kconfig  |   9 ++
> > >  drivers/hwmon/Makefile |   1 +
> > >  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > >  3 files changed, 356 insertions(+)
> > >  create mode 100644 drivers/hwmon/max127.c
> > > 
> > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > index 9d600e0c5584..716df51edc87 100644
> > > --- a/drivers/hwmon/Kconfig
> > > +++ b/drivers/hwmon/Kconfig
> > > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > >  	  This driver can also be built as a module. If so, the module
> > >  	  will be called max1111.
> > >  
> > > +config SENSORS_MAX127
> > > +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > > +	depends on I2C
> > > +	help
> > > +	  Say y here to support Maxim's MAX127 DAS chips.
> > > +
> > > +	  This driver can also be built as a module. If so, the module
> > > +	  will be called max127.
> > > +
> > >  config SENSORS_MAX16065
> > >  	tristate "Maxim MAX16065 System Manager and compatibles"
> > >  	depends on I2C
> > > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > > index 1083bbfac779..01ca5d3fbad4 100644
> > > --- a/drivers/hwmon/Makefile
> > > +++ b/drivers/hwmon/Makefile
> > > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
> > >  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
> > >  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > >  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> > > +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
> > >  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
> > >  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
> > >  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> > > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > > new file mode 100644
> > > index 000000000000..3df4c225a6a2
> > > --- /dev/null
> > > +++ b/drivers/hwmon/max127.c
> > > @@ -0,0 +1,346 @@
> > > +// SPDX-License-Identifier: GPL-2.0+
> > > +/*
> > > + * Hardware monitoring driver for MAX127.
> > > + *
> > > + * Copyright (c) 2020 Facebook Inc.
> > > + */
> > > +
> > > +#include <linux/err.h>
> > > +#include <linux/hwmon.h>
> > > +#include <linux/hwmon-sysfs.h>
> > 
> > Not needed.
> > 
> > > +#include <linux/i2c.h>
> > > +#include <linux/init.h>
> > > +#include <linux/module.h>
> > > +#include <linux/sysfs.h>
> > 
> > Not needed.
> 
> Thanks for pointing it out. Both includes are deleted in v4.
> 
> > 
> > > +
> > > +/*
> > > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > > + * Format" for details.
> > > + */
> > > +#define MAX127_CTRL_START	BIT(7)
> > > +#define MAX127_CTRL_SEL_SHIFT	4
> > > +#define MAX127_CTRL_RNG		BIT(3)
> > > +#define MAX127_CTRL_BIP		BIT(2)
> > > +#define MAX127_CTRL_PD1		BIT(1)
> > > +#define MAX127_CTRL_PD0		BIT(0)
> > > +
> > > +#define MAX127_NUM_CHANNELS	8
> > > +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > > +
> > > +/*
> > > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > > + * and Polarity Selection" for details.
> > > + */
> > > +#define MAX127_FULL_RANGE	10000	/* 10V */
> > > +#define MAX127_HALF_RANGE	5000	/* 5V */
> > > +
> > > +/*
> > > + * MAX127 returns 2 bytes at read:
> > > + *   - the first byte contains data[11:4].
> > > + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > > + * for details.
> > > + */
> > > +#define MAX127_DATA_LEN		2
> > > +#define MAX127_DATA_SHIFT	4
> > > +
> > > +#define MAX127_SIGN_BIT		BIT(11)
> > > +
> > > +struct max127_data {
> > > +	struct mutex lock;
> > > +	struct i2c_client *client;
> > > +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > > +};
> > > +
> > > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > > +{
> > > +	int status;
> > > +	struct i2c_msg msg = {
> > > +		.addr = client->addr,
> > > +		.flags = 0,
> > > +		.len = sizeof(ctrl_byte),
> > > +		.buf = &ctrl_byte,
> > > +	};
> > > +
> > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > +	if (status < 0)
> > > +		return status;
> > > +	else if (status != 1)
> > 
> > else after return is not needed.
> > 
> > > +		return -EIO;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_read_channel(struct i2c_client *client, long *val)
> > > +{
> > > +	int status;
> > > +	u8 i2c_data[MAX127_DATA_LEN];
> > > +	struct i2c_msg msg = {
> > > +		.addr = client->addr,
> > > +		.flags = I2C_M_RD,
> > > +		.len = sizeof(i2c_data),
> > > +		.buf = i2c_data,
> > > +	};
> > > +
> > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > +	if (status < 0)
> > > +		return status;
> > > +	else if (status != 1)
> > 
> > else after return is not needed.
> 
> I'm not sure if I understand your suggestion correctly, and I added this
> branch to handle the case when i2c_transfer() returns 0, which means the
> message is not transferred. Perhaps it would never happen? but anyhow, I
> just simplified the check in v4; please kindly review and let me know if
> you have further suggestions.
> 

	if (status < 0)
		return status;
	if (status != 1)
		return -EIO;

Again, else after return is not needed (and static analyzers will complain
about it).

Guenter

> > 
> > > +		return -EIO;
> > > +
> > > +	*val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> > > +		((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> > > +	return 0;
> > > +}
> > > +
> > > +static long max127_process_raw(u8 ctrl_byte, long raw)
> > > +{
> > > +	long scale, weight;
> > > +
> > > +	/*
> > > +	 * MAX127's data coding is binary in unipolar mode with 1 LSB =
> > > +	 * (Full-Scale/4096) and two’s complement binary in bipolar mode
> > > +	 * with 1 LSB = [(2 x |FS|)/4096].
> > > +	 * Refer to MAX127 datasheet, "Transfer Function" section for
> > > +	 * details.
> > > +	 */
> > > +	scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> > > +						MAX127_HALF_RANGE;
> > > +	if (ctrl_byte & MAX127_CTRL_BIP) {
> > > +		weight = (raw & MAX127_SIGN_BIT);
> > > +		raw &= ~MAX127_SIGN_BIT;
> > > +		raw -= weight;
> > > +		raw *= 2;
> > > +	}
> > > +
> > > +	return raw * scale / 4096;
> > > +}
> > > +
> > > +static int max127_read_input(struct max127_data *data, int channel, long *val)
> > > +{
> > > +	long raw;
> > > +	int status;
> > > +	struct i2c_client *client = data->client;
> > > +	u8 ctrl_byte = data->ctrl_byte[channel];
> > > +
> > > +	mutex_lock(&data->lock);
> > > +
> > > +	status = max127_select_channel(client, ctrl_byte);
> > > +	if (status)
> > > +		goto exit;
> > > +
> > > +	status = max127_read_channel(client, &raw);
> > > +	if (status)
> > > +		goto exit;
> > > +
> > > +	*val = max127_process_raw(ctrl_byte, raw);
> > > +
> > > +exit:
> > > +	mutex_unlock(&data->lock);
> > > +	return status;
> > > +}
> > > +
> > > +static int max127_read_min(struct max127_data *data, int channel, long *val)
> > > +{
> > > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > > +	static const int min_input_map[4] = {
> > > +		0,			/* RNG=0, BIP=0 */
> > > +		-MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > > +		0,			/* RNG=1, BIP=0 */
> > > +		-MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > > +	};
> > > +
> > > +	*val = min_input_map[rng_bip];
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_read_max(struct max127_data *data, int channel, long *val)
> > > +{
> > > +	u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > > +	static const int max_input_map[4] = {
> > > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=0 */
> > > +		MAX127_HALF_RANGE,	/* RNG=0, BIP=1 */
> > > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=0 */
> > > +		MAX127_FULL_RANGE,	/* RNG=1, BIP=1 */
> > > +	};
> > > +
> > > +	*val = max_input_map[rng_bip];
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_write_min(struct max127_data *data, int channel, long val)
> > > +{
> > > +	u8 ctrl;
> > > +
> > > +	ctrl = data->ctrl_byte[channel];
> > > +	if (val <= -MAX127_FULL_RANGE) {
> > > +		ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> > > +	} else if (val < 0) {
> > > +		ctrl |= MAX127_CTRL_BIP;
> > > +		ctrl &= ~MAX127_CTRL_RNG;
> > > +	} else {
> > > +		ctrl &= ~MAX127_CTRL_BIP;
> > > +	}
> > > +	data->ctrl_byte[channel] = ctrl;
> > 
> > Needs mutex protection to avoid parallel writes (which might mess up
> > ctrl_byte[channel]).
> > 
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_write_max(struct max127_data *data, int channel, long val)
> > > +{
> > > +	if (val >= MAX127_FULL_RANGE)
> > > +		data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> > > +	else
> > > +		data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> > > +
> > Same here, to avoid interaction with write_min (which might otherwise
> > read ctrl and modify it at the same time as this function).
> 
> Thanks for pointing it out, and both functions are protected by mutex in
> v4.
> 
> 
> Cheers,
> 
> Tao
> 
> > 
> > > +	return 0;
> > > +}
> > > +
> > > +static umode_t max127_is_visible(const void *_data,
> > > +				 enum hwmon_sensor_types type,
> > > +				 u32 attr, int channel)
> > > +{
> > > +	if (type == hwmon_in) {
> > > +		switch (attr) {
> > > +		case hwmon_in_input:
> > > +			return 0444;
> > > +
> > > +		case hwmon_in_min:
> > > +		case hwmon_in_max:
> > > +			return 0644;
> > > +
> > > +		default:
> > > +			break;
> > > +		}
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> > > +			u32 attr, int channel, long *val)
> > > +{
> > > +	int status;
> > > +	struct max127_data *data = dev_get_drvdata(dev);
> > > +
> > > +	if (type != hwmon_in)
> > > +		return -EOPNOTSUPP;
> > > +
> > > +	switch (attr) {
> > > +	case hwmon_in_input:
> > > +		status = max127_read_input(data, channel, val);
> > > +		break;
> > > +
> > > +	case hwmon_in_min:
> > > +		status = max127_read_min(data, channel, val);
> > > +		break;
> > > +
> > > +	case hwmon_in_max:
> > > +		status = max127_read_max(data, channel, val);
> > > +		break;
> > > +
> > > +	default:
> > > +		status = -EOPNOTSUPP;
> > > +		break;
> > > +	}
> > > +
> > > +	return status;
> > > +}
> > > +
> > > +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> > > +			u32 attr, int channel, long val)
> > > +{
> > > +	int status;
> > > +	struct max127_data *data = dev_get_drvdata(dev);
> > > +
> > > +	if (type != hwmon_in)
> > > +		return -EOPNOTSUPP;
> > > +
> > > +	switch (attr) {
> > > +	case hwmon_in_min:
> > > +		status = max127_write_min(data, channel, val);
> > > +		break;
> > > +
> > > +	case hwmon_in_max:
> > > +		status = max127_write_max(data, channel, val);
> > > +		break;
> > > +
> > > +	default:
> > > +		status = -EOPNOTSUPP;
> > > +		break;
> > > +	}
> > > +
> > > +	return status;
> > > +}
> > > +
> > > +static const struct hwmon_ops max127_hwmon_ops = {
> > > +	.is_visible = max127_is_visible,
> > > +	.read = max127_read,
> > > +	.write = max127_write,
> > > +};
> > > +
> > > +static const struct hwmon_channel_info *max127_info[] = {
> > > +	HWMON_CHANNEL_INFO(in,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > +			   HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> > > +	NULL,
> > > +};
> > > +
> > > +static const struct hwmon_chip_info max127_chip_info = {
> > > +	.ops = &max127_hwmon_ops,
> > > +	.info = max127_info,
> > > +};
> > > +
> > > +static int max127_probe(struct i2c_client *client,
> > > +			const struct i2c_device_id *id)
> > > +{
> > > +	int i;
> > > +	struct device *hwmon_dev;
> > > +	struct max127_data *data;
> > > +	struct device *dev = &client->dev;
> > > +
> > > +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > > +	if (!data)
> > > +		return -ENOMEM;
> > > +
> > > +	data->client = client;
> > > +	mutex_init(&data->lock);
> > > +	for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> > > +		data->ctrl_byte[i] = (MAX127_CTRL_START |
> > > +				      MAX127_SET_CHANNEL(i));
> > > +
> > > +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> > > +							 data,
> > > +							 &max127_chip_info,
> > > +							 NULL);
> > > +
> > > +	return PTR_ERR_OR_ZERO(hwmon_dev);
> > > +}
> > > +
> > > +static const struct i2c_device_id max127_id[] = {
> > > +	{ "max127", 0 },
> > > +	{ }
> > > +};
> > > +MODULE_DEVICE_TABLE(i2c, max127_id);
> > > +
> > > +static struct i2c_driver max127_driver = {
> > > +	.class		= I2C_CLASS_HWMON,
> > > +	.driver = {
> > > +		.name	= "max127",
> > > +	},
> > > +	.probe		= max127_probe,
> > > +	.id_table	= max127_id,
> > > +};
> > > +
> > > +module_i2c_driver(max127_driver);
> > > +
> > > +MODULE_LICENSE("GPL");
> > > +MODULE_AUTHOR("Mike Choi <mikechoi@fb.com>");
> > > +MODULE_AUTHOR("Tao Ren <rentao.bupt@gmail.com>");
> > > +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Tao Ren]

On Mon, Nov 23, 2020 at 05:16:41AM -0800, Guenter Roeck wrote:
> On Sun, Nov 22, 2020 at 11:54:49PM -0800, Tao Ren wrote:
> > On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> > > On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> > > > From: Tao Ren <rentao.bupt@gmail.com>
> > > > 
> > > > Add hardware monitoring driver for the Maxim MAX127 chip.
> > > > 
> > > > MAX127 min/max range handling code is inspired by the max197 driver.
> > > > 
> > > > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> > > 
> > > Nice cleanup. Couple of minor comments.
> > > 
> > > Thanks,
> > > Guenter
> > > 
> > > > ---
> > > >  Changes in v3:
> > > >    - no code change. xdp maintainers were removed from to/cc list.
> > > >  Changes in v2:
> > > >    - replace devm_hwmon_device_register_with_groups() with
> > > >      devm_hwmon_device_register_with_info() API.
> > > >    - divide min/max read and write methods to separate functions.
> > > >    - fix raw-to-vin conversion logic.
> > > >    - refine ctrl_byte handling so mutex is not needed to protect the
> > > >      byte.
> > > >    - improve i2c_transfer() error handling.
> > > >    - a few other improvements (comments, variable naming, and etc.).
> > > > 
> > > >  drivers/hwmon/Kconfig  |   9 ++
> > > >  drivers/hwmon/Makefile |   1 +
> > > >  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > > >  3 files changed, 356 insertions(+)
> > > >  create mode 100644 drivers/hwmon/max127.c
> > > > 
> > > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > > index 9d600e0c5584..716df51edc87 100644
> > > > --- a/drivers/hwmon/Kconfig
> > > > +++ b/drivers/hwmon/Kconfig
> > > > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > > >  	  This driver can also be built as a module. If so, the module
> > > >  	  will be called max1111.
> > > >  
> > > > +config SENSORS_MAX127
> > > > +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > > > +	depends on I2C
> > > > +	help
> > > > +	  Say y here to support Maxim's MAX127 DAS chips.
> > > > +
> > > > +	  This driver can also be built as a module. If so, the module
> > > > +	  will be called max127.
> > > > +
> > > >  config SENSORS_MAX16065
> > > >  	tristate "Maxim MAX16065 System Manager and compatibles"
> > > >  	depends on I2C
> > > > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > > > index 1083bbfac779..01ca5d3fbad4 100644
> > > > --- a/drivers/hwmon/Makefile
> > > > +++ b/drivers/hwmon/Makefile
> > > > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
> > > >  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
> > > >  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > > >  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> > > > +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
> > > >  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
> > > >  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
> > > >  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> > > > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > > > new file mode 100644
> > > > index 000000000000..3df4c225a6a2
> > > > --- /dev/null
> > > > +++ b/drivers/hwmon/max127.c
> > > > @@ -0,0 +1,346 @@
> > > > +// SPDX-License-Identifier: GPL-2.0+
> > > > +/*
> > > > + * Hardware monitoring driver for MAX127.
> > > > + *
> > > > + * Copyright (c) 2020 Facebook Inc.
> > > > + */
> > > > +
> > > > +#include <linux/err.h>
> > > > +#include <linux/hwmon.h>
> > > > +#include <linux/hwmon-sysfs.h>
> > > 
> > > Not needed.
> > > 
> > > > +#include <linux/i2c.h>
> > > > +#include <linux/init.h>
> > > > +#include <linux/module.h>
> > > > +#include <linux/sysfs.h>
> > > 
> > > Not needed.
> > 
> > Thanks for pointing it out. Both includes are deleted in v4.
> > 
> > > 
> > > > +
> > > > +/*
> > > > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > > > + * Format" for details.
> > > > + */
> > > > +#define MAX127_CTRL_START	BIT(7)
> > > > +#define MAX127_CTRL_SEL_SHIFT	4
> > > > +#define MAX127_CTRL_RNG		BIT(3)
> > > > +#define MAX127_CTRL_BIP		BIT(2)
> > > > +#define MAX127_CTRL_PD1		BIT(1)
> > > > +#define MAX127_CTRL_PD0		BIT(0)
> > > > +
> > > > +#define MAX127_NUM_CHANNELS	8
> > > > +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > > > +
> > > > +/*
> > > > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > > > + * and Polarity Selection" for details.
> > > > + */
> > > > +#define MAX127_FULL_RANGE	10000	/* 10V */
> > > > +#define MAX127_HALF_RANGE	5000	/* 5V */
> > > > +
> > > > +/*
> > > > + * MAX127 returns 2 bytes at read:
> > > > + *   - the first byte contains data[11:4].
> > > > + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > > > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > > > + * for details.
> > > > + */
> > > > +#define MAX127_DATA_LEN		2
> > > > +#define MAX127_DATA_SHIFT	4
> > > > +
> > > > +#define MAX127_SIGN_BIT		BIT(11)
> > > > +
> > > > +struct max127_data {
> > > > +	struct mutex lock;
> > > > +	struct i2c_client *client;
> > > > +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > > > +};
> > > > +
> > > > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > > > +{
> > > > +	int status;
> > > > +	struct i2c_msg msg = {
> > > > +		.addr = client->addr,
> > > > +		.flags = 0,
> > > > +		.len = sizeof(ctrl_byte),
> > > > +		.buf = &ctrl_byte,
> > > > +	};
> > > > +
> > > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > > +	if (status < 0)
> > > > +		return status;
> > > > +	else if (status != 1)
> > > 
> > > else after return is not needed.
> > > 
> > > > +		return -EIO;
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int max127_read_channel(struct i2c_client *client, long *val)
> > > > +{
> > > > +	int status;
> > > > +	u8 i2c_data[MAX127_DATA_LEN];
> > > > +	struct i2c_msg msg = {
> > > > +		.addr = client->addr,
> > > > +		.flags = I2C_M_RD,
> > > > +		.len = sizeof(i2c_data),
> > > > +		.buf = i2c_data,
> > > > +	};
> > > > +
> > > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > > +	if (status < 0)
> > > > +		return status;
> > > > +	else if (status != 1)
> > > 
> > > else after return is not needed.
> > 
> > I'm not sure if I understand your suggestion correctly, and I added this
> > branch to handle the case when i2c_transfer() returns 0, which means the
> > message is not transferred. Perhaps it would never happen? but anyhow, I
> > just simplified the check in v4; please kindly review and let me know if
> > you have further suggestions.
> > 
> 
> 	if (status < 0)
> 		return status;
> 	if (status != 1)
> 		return -EIO;
> 
> Again, else after return is not needed (and static analyzers will complain
> about it).
> 
> Guenter

Ahh, I get it now (I didn't know static analyzers would complain about
it). Thanks for the sharing, and it's fixed in v5.


Cheers,

Tao

Re: [PATCH v3 1/2] hwmon: (max127) Add Maxim MAX127 hardware monitoring driver

[Tao Ren]

On Mon, Nov 23, 2020 at 05:16:41AM -0800, Guenter Roeck wrote:
> On Sun, Nov 22, 2020 at 11:54:49PM -0800, Tao Ren wrote:
> > On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> > > On Thu, Nov 19, 2020 at 09:53:23AM -0800, rentao.bupt@gmail.com wrote:
> > > > From: Tao Ren <rentao.bupt@gmail.com>
> > > > 
> > > > Add hardware monitoring driver for the Maxim MAX127 chip.
> > > > 
> > > > MAX127 min/max range handling code is inspired by the max197 driver.
> > > > 
> > > > Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
> > > 
> > > Nice cleanup. Couple of minor comments.
> > > 
> > > Thanks,
> > > Guenter
> > > 
> > > > ---
> > > >  Changes in v3:
> > > >    - no code change. xdp maintainers were removed from to/cc list.
> > > >  Changes in v2:
> > > >    - replace devm_hwmon_device_register_with_groups() with
> > > >      devm_hwmon_device_register_with_info() API.
> > > >    - divide min/max read and write methods to separate functions.
> > > >    - fix raw-to-vin conversion logic.
> > > >    - refine ctrl_byte handling so mutex is not needed to protect the
> > > >      byte.
> > > >    - improve i2c_transfer() error handling.
> > > >    - a few other improvements (comments, variable naming, and etc.).
> > > > 
> > > >  drivers/hwmon/Kconfig  |   9 ++
> > > >  drivers/hwmon/Makefile |   1 +
> > > >  drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > > >  3 files changed, 356 insertions(+)
> > > >  create mode 100644 drivers/hwmon/max127.c
> > > > 
> > > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > > index 9d600e0c5584..716df51edc87 100644
> > > > --- a/drivers/hwmon/Kconfig
> > > > +++ b/drivers/hwmon/Kconfig
> > > > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > > >  	  This driver can also be built as a module. If so, the module
> > > >  	  will be called max1111.
> > > >  
> > > > +config SENSORS_MAX127
> > > > +	tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > > > +	depends on I2C
> > > > +	help
> > > > +	  Say y here to support Maxim's MAX127 DAS chips.
> > > > +
> > > > +	  This driver can also be built as a module. If so, the module
> > > > +	  will be called max127.
> > > > +
> > > >  config SENSORS_MAX16065
> > > >  	tristate "Maxim MAX16065 System Manager and compatibles"
> > > >  	depends on I2C
> > > > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > > > index 1083bbfac779..01ca5d3fbad4 100644
> > > > --- a/drivers/hwmon/Makefile
> > > > +++ b/drivers/hwmon/Makefile
> > > > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
> > > >  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
> > > >  obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > > >  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
> > > > +obj-$(CONFIG_SENSORS_MAX127)	+= max127.o
> > > >  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
> > > >  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
> > > >  obj-$(CONFIG_SENSORS_MAX1668)	+= max1668.o
> > > > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > > > new file mode 100644
> > > > index 000000000000..3df4c225a6a2
> > > > --- /dev/null
> > > > +++ b/drivers/hwmon/max127.c
> > > > @@ -0,0 +1,346 @@
> > > > +// SPDX-License-Identifier: GPL-2.0+
> > > > +/*
> > > > + * Hardware monitoring driver for MAX127.
> > > > + *
> > > > + * Copyright (c) 2020 Facebook Inc.
> > > > + */
> > > > +
> > > > +#include <linux/err.h>
> > > > +#include <linux/hwmon.h>
> > > > +#include <linux/hwmon-sysfs.h>
> > > 
> > > Not needed.
> > > 
> > > > +#include <linux/i2c.h>
> > > > +#include <linux/init.h>
> > > > +#include <linux/module.h>
> > > > +#include <linux/sysfs.h>
> > > 
> > > Not needed.
> > 
> > Thanks for pointing it out. Both includes are deleted in v4.
> > 
> > > 
> > > > +
> > > > +/*
> > > > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > > > + * Format" for details.
> > > > + */
> > > > +#define MAX127_CTRL_START	BIT(7)
> > > > +#define MAX127_CTRL_SEL_SHIFT	4
> > > > +#define MAX127_CTRL_RNG		BIT(3)
> > > > +#define MAX127_CTRL_BIP		BIT(2)
> > > > +#define MAX127_CTRL_PD1		BIT(1)
> > > > +#define MAX127_CTRL_PD0		BIT(0)
> > > > +
> > > > +#define MAX127_NUM_CHANNELS	8
> > > > +#define MAX127_SET_CHANNEL(ch)	(((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > > > +
> > > > +/*
> > > > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > > > + * and Polarity Selection" for details.
> > > > + */
> > > > +#define MAX127_FULL_RANGE	10000	/* 10V */
> > > > +#define MAX127_HALF_RANGE	5000	/* 5V */
> > > > +
> > > > +/*
> > > > + * MAX127 returns 2 bytes at read:
> > > > + *   - the first byte contains data[11:4].
> > > > + *   - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > > > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > > > + * for details.
> > > > + */
> > > > +#define MAX127_DATA_LEN		2
> > > > +#define MAX127_DATA_SHIFT	4
> > > > +
> > > > +#define MAX127_SIGN_BIT		BIT(11)
> > > > +
> > > > +struct max127_data {
> > > > +	struct mutex lock;
> > > > +	struct i2c_client *client;
> > > > +	u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > > > +};
> > > > +
> > > > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > > > +{
> > > > +	int status;
> > > > +	struct i2c_msg msg = {
> > > > +		.addr = client->addr,
> > > > +		.flags = 0,
> > > > +		.len = sizeof(ctrl_byte),
> > > > +		.buf = &ctrl_byte,
> > > > +	};
> > > > +
> > > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > > +	if (status < 0)
> > > > +		return status;
> > > > +	else if (status != 1)
> > > 
> > > else after return is not needed.
> > > 
> > > > +		return -EIO;
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int max127_read_channel(struct i2c_client *client, long *val)
> > > > +{
> > > > +	int status;
> > > > +	u8 i2c_data[MAX127_DATA_LEN];
> > > > +	struct i2c_msg msg = {
> > > > +		.addr = client->addr,
> > > > +		.flags = I2C_M_RD,
> > > > +		.len = sizeof(i2c_data),
> > > > +		.buf = i2c_data,
> > > > +	};
> > > > +
> > > > +	status = i2c_transfer(client->adapter, &msg, 1);
> > > > +	if (status < 0)
> > > > +		return status;
> > > > +	else if (status != 1)
> > > 
> > > else after return is not needed.
> > 
> > I'm not sure if I understand your suggestion correctly, and I added this
> > branch to handle the case when i2c_transfer() returns 0, which means the
> > message is not transferred. Perhaps it would never happen? but anyhow, I
> > just simplified the check in v4; please kindly review and let me know if
> > you have further suggestions.
> > 
> 
> 	if (status < 0)
> 		return status;
> 	if (status != 1)
> 		return -EIO;
> 
> Again, else after return is not needed (and static analyzers will complain
> about it).
> 
> Guenter

Ahh, I get it now (I didn't know static analyzers would complain about
it). Thanks for the sharing, and it's fixed in v5.


Cheers,

Tao