Re: [PATCH v2 1/3] pmbus: introduce PMBUS_VIRT_*_SAMPLES registers

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On 4/13/19 9:03 AM, Adamski, Krzysztof (Nokia - PL/Wroclaw) wrote:
Those virtual registers can be used to export manufacturer specific
functionality for controlling the number of samples for average values
reported by the device.

Signed-off-by: Krzysztof Adamski <krzysztof.adamski@xxxxxxxxx>
---
  Documentation/hwmon/sysfs-interface |  18 +++++
  drivers/hwmon/pmbus/pmbus.h         |  15 ++++
  drivers/hwmon/pmbus/pmbus_core.c    | 114 ++++++++++++++++++++++++++++
  3 files changed, 147 insertions(+)

diff --git a/Documentation/hwmon/sysfs-interface b/Documentation/hwmon/sysfs-interface
index 2b9e1005d88b..7b91706d01c8 100644
--- a/Documentation/hwmon/sysfs-interface
+++ b/Documentation/hwmon/sysfs-interface
@@ -756,6 +756,24 @@ intrusion[0-*]_beep
  		1: enable
  		RW
+********************************
+* Average sample configuration *
+********************************
+
+Devices allowing for reading {in,power,curr,temp}_average values may export
+attributes for controlling number of samples used to compute average.
+
+samples		Sets number of average samples for all types of measurements.
+		RW
+
+in_samples
+power_samples
+curr_samples
+temp_samples    Sets number of average samples for specific type of measurements.
+		Note that on some devices it won't be possible to set all of them
+		to different values so changing one might also change some others.
+		RW
+

Separate patch for the above, please. Adding the ABI is one subject, adding support
for it into a driver (or driver core) is another.


  sysfs attribute writes interpretation
  -------------------------------------
diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index 1d24397d36ec..e73289cc867d 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -217,6 +217,20 @@ enum pmbus_regs {
  	PMBUS_VIRT_PWM_ENABLE_2,
  	PMBUS_VIRT_PWM_ENABLE_3,
  	PMBUS_VIRT_PWM_ENABLE_4,
+
+	/* Samples for average
+	 *
+	 * Drivers wanting to expose functionality for changing the number of
+	 * samples used for average values should implement support in
+	 * {read,write}_word_data callback for either PMBUS_VIRT_SAMPLES if it
+	 * applies to all types of measurements, or any number of specific
+	 * PMBUS_VIRT_*_SAMPLES registers to allow for individual control.
+	 */
+	PMBUS_VIRT_SAMPLES,
+	PMBUS_VIRT_IN_SAMPLES,
+	PMBUS_VIRT_CURR_SAMPLES,
+	PMBUS_VIRT_POWER_SAMPLES,
+	PMBUS_VIRT_TEMP_SAMPLES,
  };
/*
@@ -371,6 +385,7 @@ enum pmbus_sensor_classes {
  #define PMBUS_HAVE_STATUS_VMON	BIT(19)
  #define PMBUS_HAVE_PWM12	BIT(20)
  #define PMBUS_HAVE_PWM34	BIT(21)
+#define PMBUS_HAVE_SAMPLES	BIT(22)
#define PMBUS_PAGE_VIRTUAL BIT(31) diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 2e2b5851139c..31b6bf49518c 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -1901,6 +1901,116 @@ static int pmbus_add_fan_attributes(struct i2c_client *client,
  	return 0;
  }
+struct pmbus_samples_attr {
+	int reg;
+	char *name;
+};
+
+struct pmbus_samples_reg {
+	int page;
+	struct pmbus_samples_attr *attr;
+	struct device_attribute dev_attr;
+};
+
+static struct pmbus_samples_attr pmbus_samples_registers[] = {
+	{
+		.reg = PMBUS_VIRT_SAMPLES,
+		.name = "samples",
+	}, {
+		.reg = PMBUS_VIRT_IN_SAMPLES,
+		.name = "in_samples",
+	}, {
+		.reg = PMBUS_VIRT_CURR_SAMPLES,
+		.name = "curr_samples",
+	}, {
+		.reg = PMBUS_VIRT_POWER_SAMPLES,
+		.name = "power_samples",
+	}, {
+		.reg = PMBUS_VIRT_TEMP_SAMPLES,
+		.name = "temp_samples",
+	}
+};
+
+#define to_samples_reg(x) container_of(x, struct pmbus_samples_reg, dev_attr)
+
+static ssize_t pmbus_show_samples(struct device *dev,
+				  struct device_attribute *devattr, char *buf)
+{
+	int val;
+	struct i2c_client *client = to_i2c_client(dev->parent);
+	struct pmbus_samples_reg *reg = to_samples_reg(devattr);
+
+	val = _pmbus_read_word_data(client, reg->page, reg->attr->reg);
+	if (val < 0)
+		return val;
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+
+static ssize_t pmbus_set_samples(struct device *dev,
+				 struct device_attribute *devattr,
+				 const char *buf, size_t count)
+{
+	int ret;
+	long val;
+	struct i2c_client *client = to_i2c_client(dev->parent);
+	struct pmbus_samples_reg *reg = to_samples_reg(devattr);
+
+	if (kstrtol(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	ret = _pmbus_write_word_data(client, reg->page, reg->attr->reg, val);
+
+	return ret ? : count;
+}
+
+static int pmbus_add_samples_attr(struct pmbus_data *data, int page,
+				  struct pmbus_samples_attr *attr)
+{
+	struct pmbus_samples_reg *reg;
+
+	reg = devm_kzalloc(data->dev, sizeof(*reg), GFP_KERNEL);
+	if (!reg)
+		return -ENOMEM;
+
+	reg->attr = attr;
+	reg->page = page;
+
+	pmbus_dev_attr_init(&reg->dev_attr, attr->name, (S_IWUSR | S_IRUGO),

S_IWUSR ran out of favor and generates a checkpatch warning.
Please use 0644.

+			    pmbus_show_samples, pmbus_set_samples);
+
+	return pmbus_add_attribute(data, &reg->dev_attr.attr);
+}
+
+static int pmbus_add_samples_attributes(struct i2c_client *client,
+					struct pmbus_data *data)
+{
+	const struct pmbus_driver_info *info = data->info;
+	int page;
+
+	for (page = 0; page < info->pages; page++) {

This won't work as intended on multi-page chips. If the driver writer
is not careful, it will try to generate multiple similar attributes,
one per page. I would suggest to only check this for page 0.
At some point we may need to add a separate func pointer for
chip specific attributes, but that should do for now.

+		int s;:
+
+		if (!(info->func[page] & PMBUS_HAVE_SAMPLES))
+			continue;
+
+		for (s = 0; s < ARRAY_SIZE(pmbus_samples_registers); s++) {
+			int ret;
+			struct pmbus_samples_attr *attr;
+

Please use reverse christmas tree here

			struct pmbus_samples_attr *attr;
			int ret;

+			attr = &pmbus_samples_registers[s];
+			if (!pmbus_check_word_register(client, page, attr->reg))
+				continue;
+
+			ret = pmbus_add_samples_attr(data, page, attr);
+			if (ret)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
  static int pmbus_find_attributes(struct i2c_client *client,
  				 struct pmbus_data *data)
  {
@@ -1932,6 +2042,10 @@ static int pmbus_find_attributes(struct i2c_client *client,
/* Fans */
  	ret = pmbus_add_fan_attributes(client, data);
+	if (ret)
+		return ret;
+
+	ret = pmbus_add_samples_attributes(client, data);
  	return ret;
  }




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