Re: [PATCH v4 2/3] iio: add MEMSensing MSA311 3-axis accelerometer driver

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Le 03/08/2022 à 20:39, Dmitry Rokosov a écrit :
Hello Christophe,

Thank you for quick review

On Wed, Aug 03, 2022 at 08:11:05PM +0200, Christophe JAILLET wrote:
Le 03/08/2022 à 15:11, Dmitry Rokosov a écrit :
MSA311 is a tri-axial, low-g accelerometer with I2C digital output for
sensitivity consumer applications. It has dynamic user-selectable full
scales range of +-2g/+-4g/+-8g/+-16g and allows acceleration measurements
with output data rates from 1Hz to 1000Hz.

Spec: https://cdn-shop.adafruit.com/product-files/5309/MSA311-V1.1-ENG.pdf

This driver supports following MSA311 features:
      - IIO interface
      - Different power modes: NORMAL and SUSPEND (using pm_runtime)
      - ODR (Output Data Rate) selection
      - Scale and samp_freq selection
      - IIO triggered buffer, IIO reg access
      - NEW_DATA interrupt + trigger

Below features to be done:
      - Motion Events: ACTIVE, TAP, ORIENT, FREEFALL
      - Low Power mode

Signed-off-by: Dmitry Rokosov <ddrokosov-i4r8oA+eLlH99rHkP+FxIw@xxxxxxxxxxxxxxxx>
---
   MAINTAINERS                |    6 +
   drivers/iio/accel/Kconfig  |   13 +
   drivers/iio/accel/Makefile |    2 +
   drivers/iio/accel/msa311.c | 1323 ++++++++++++++++++++++++++++++++++++
   4 files changed, 1344 insertions(+)
   create mode 100644 drivers/iio/accel/msa311.c


Hi,
a few nits below.

[...]

+static int msa311_check_partid(struct msa311_priv *msa311)
+{
+	struct device *dev = msa311->dev;
+	unsigned int partid;
+	int err;
+
+	err = regmap_read(msa311->regs, MSA311_PARTID_REG, &partid);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "failed to read partid (%d)\n", err);

No need for "(%d)" and err.


Do you mean for all dev_err() calls? I think sometimes it's helpful to
know the actual error value got from external API, isn't? Could you please
explain your point if possible?


No, my comment is only for dev_err_probe() function.
Having ret for dev_err() calls is fine.

See: https://elixir.bootlin.com/linux/v5.19/source/drivers/base/core.c#L4732

dev_err_probe() already has a "error %pe:..., ERR_PTR(err)"
This means that if ret = -ENOMEM:
   "(%d)"       --> "(-12)"
   "error %pe:" --> "error -ENOMEM:"

So there is no real need to duplicate the error code in the message itself, it is already displayed in a human readable manner.

What your code does would result in:
   "error -ENOMEM: failed to read partid (-12)\n"

+
+	if (partid == MSA311_WHO_AM_I)
+		dev_dbg(dev, "found MSA311 compatible chip[%#x]\n", partid);
+	else
+		dev_warn(dev, "invalid partid (%#x), expected (%#x)\n",
+			 partid, MSA311_WHO_AM_I);
+
+	return 0;
+}

[...]

+static int msa311_probe(struct i2c_client *i2c)
+{
+	struct device *dev = &i2c->dev;
+	struct msa311_priv *msa311;
+	struct iio_dev *indio_dev;
+	int err;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*msa311));
+	if (!indio_dev)
+		return dev_err_probe(dev, -ENOMEM,
+				     "iio device allocation failed\n");
+
+	msa311 = iio_priv(indio_dev);
+	msa311->dev = dev;
+	i2c_set_clientdata(i2c, indio_dev);
+
+	err = msa311_regmap_init(msa311);
+	if (err)
+		return err;
+
+	mutex_init(&msa311->lock);
+
+	msa311->vdd = devm_regulator_get_optional(dev, "vdd");
+	if (IS_ERR(msa311->vdd)) {
+		err = PTR_ERR(msa311->vdd);
+		if (err == -ENODEV)
+			msa311->vdd = NULL;
+		else
+			return dev_err_probe(dev, PTR_ERR(msa311->vdd),
+					     "cannot get vdd supply\n");
+	}
+
+	if (msa311->vdd) {
+		err = regulator_enable(msa311->vdd);
+		if (err)
+			return dev_err_probe(dev, err,
+					     "cannot enable vdd supply\n");
+
+		err = devm_add_action_or_reset(dev, msa311_vdd_disable,
+					       msa311->vdd);
+		if (err) {
+			regulator_disable(msa311->vdd);

Double regulator_disable(), because of the _or_reset()?


Yep. If devm_add_action_or_reset() returns an error, we will not
call regulator_disable() by devm subsystem. It means, we have to
call it directly.

No.

See https://elixir.bootlin.com/linux/v5.19/source/include/linux/device.h#L249

If devm_add_action_or_reset() fails, "action" is called. This is the meaning of the _or_reset suffix.

So here, msa311_vdd_disable() would be called and this function is:

+static void msa311_vdd_disable(void *vdd)
+{
+	regulator_disable(vdd);
+}

and "vdd" will be the value of "msa311->vdd"

So, unless I missed something obvious, your code will call twice regulator_disable(msa311->vdd).

One in devm_add_action_or_reset() and one explicitly after the "if (err)"


Hoping I'm clear and that I didn't miss something obvious.

CJ


+			return dev_err_probe(dev, err,
+					     "cannot add vdd disable action\n");
+		}
+	}
+
+	err = msa311_check_partid(msa311);
+	if (err)
+		return err;
+
+	err = msa311_soft_reset(msa311);
+	if (err)
+		return err;
+
+	err = msa311_set_pwr_mode(msa311, MSA311_PWR_MODE_NORMAL);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "failed to power on device (%d)\n", err);

No need for "(%d)" and err

Asked for the clarification above.


CJ





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