iio:magnetometer:ak8975: fix and enhancements

ak_def_array bounds are not properly checked in case of ACPI matching failure. GCC warns with the following message at line 799:
‘chipset’ may be used uninitialized in this function.

Signed-off-by Gregor Boirie <[email protected]>

---
 drivers/iio/magnetometer/ak8975.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

drivers/iio/magnetometer/ak8975.c +4 -1

index 9c5c9ef..11059b2 100644
@@ -774,8 +774,11 @@ static int ak8975_probe(struct i2c_client *client,
 	if (id) {
 		chipset = (enum asahi_compass_chipset)(id->driver_data);
 		name = id->name;
-	} else if (ACPI_HANDLE(&client->dev))
+	} else if (ACPI_HANDLE(&client->dev)) {
 		name = ak8975_match_acpi_device(&client->dev, &chipset);
+		if (!name)
+			return -ENODEV;
+	}
 	else
 		return -ENOSYS;
 

Remove unused struct ak8975_data attrs field.

Signed-off-by Gregor Boirie <[email protected]>

---
 drivers/iio/magnetometer/ak8975.c | 1 -
 1 file changed, 1 deletion(-)

drivers/iio/magnetometer/ak8975.c +0 -1

index 11059b2..896b13e3 100644
@@ -361,7 +361,6 @@ static const struct ak_def ak_def_array[AK_MAX_TYPE] = {
 struct ak8975_data {
 	struct i2c_client	*client;
 	const struct ak_def	*def;
-	struct attribute_group	attrs;
 	struct mutex		lock;
 	u8			asa[3];
 	long			raw_to_gauss[3];

Add support for an optional regulator which, if found into device-tree, will power on device at probing time.
The regulator is declared into ak8975 DTS entry as a "vdd-supply" property.

Signed-off-by Gregor Boirie <[email protected]>

---
 .../devicetree/bindings/iio/magnetometer/ak8975.txt      |  2 ++
 drivers/iio/magnetometer/ak8975.c                        | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt +2 -0

index 011679f..34a3206 100644
@@ -8,6 +8,7 @@ Required properties:
 Optional properties:
 
   - gpios : should be device tree identifier of the magnetometer DRDY pin
+  - vdd-supply: an optional regulator that needs to be on to provide VDD
 
 Example:
 

@@ -15,4 +16,5 @@ ak8975@0c {
         compatible = "asahi-kasei,ak8975";
         reg = <0x0c>;
         gpios = <&gpj0 7 0>;
+        vdd-supply = <&ldo_3v3_gnss>;
 };

drivers/iio/magnetometer/ak8975.c +16 -0

index 896b13e3..72c03d9 100644
@@ -32,6 +32,7 @@
 #include <linux/gpio.h>
 #include <linux/of_gpio.h>
 #include <linux/acpi.h>
+#include <linux/regulator/consumer.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>

@@ -379,8 +380,23 @@ static int ak8975_who_i_am(struct i2c_client *client,
 			   enum asahi_compass_chipset type)
 {
 	u8 wia_val[2];
+	struct regulator *vdd = devm_regulator_get_optional(&client->dev,
+							    "vdd");
 	int ret;
 
+	/* Enable attached regulator if any. */
+	if (!IS_ERR(vdd)) {
+		ret = regulator_enable(vdd);
+		if (ret) {
+			dev_err(&client->dev, "Failed to enable Vdd supply\n");
+			return ret;
+		}
+	} else {
+		ret = PTR_ERR(vdd);
+		if (ret != -ENODEV)
+			return ret;
+	}
+
 	/*
 	 * Signature for each device:
 	 * Device   |  WIA1      |  WIA2

Expose a rotation matrix to indicate userspace the chip placement with respect to the overall hardware system. This is needed to adjust coordinates sampled from a magnetometer chip when its position deviates from the main hardware system.

Final coordinates computation is delegated to userspace since:
* computation may involve floating point arithmetics ;
* it allows an application to combine adjustments with arbitrary transformations.

This 3 dimentional space rotation matrix is expressed as 3x3 array of strings to support floating point numbers. It may be retrieved from a "in_magn_matrix" sysfs attribute file. It is declared into ak8975 DTS entry as a "matrix" property.

Signed-off-by Gregor Boirie <[email protected]>

---
 .../bindings/iio/magnetometer/ak8975.txt           | 10 +++++
 drivers/iio/magnetometer/ak8975.c                  | 46 +++++++++++++++++++++-
 2 files changed, 55 insertions(+), 1 deletion(-)

Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt +10 -0

index 34a3206..f936f86 100644
@@ -9,6 +9,7 @@ Optional properties:
 
   - gpios : should be device tree identifier of the magnetometer DRDY pin
   - vdd-supply: an optional regulator that needs to be on to provide VDD
+  - matrix: an optional 3x3 mounting rotation matrix
 
 Example:
 

@@ -17,4 +18,13 @@ ak8975@0c {
         reg = <0x0c>;
         gpios = <&gpj0 7 0>;
         vdd-supply = <&ldo_3v3_gnss>;
+        matrix = "-0.984807753012208",  /* x0 */
+                 "0",                   /* y0 */
+                 "-0.173648177666930",  /* z0 */
+                 "0",                   /* x1 */
+                 "-1",                  /* y1 */
+                 "0",                   /* z1 */
+                 "-0.173648177666930",  /* x2 */
+                 "0",                   /* y2 */
+                 "0.984807753012208";   /* z2 */
 };

drivers/iio/magnetometer/ak8975.c +45 -1

index 72c03d9..95c68952 100644
@@ -370,6 +370,7 @@ struct ak8975_data {
 	wait_queue_head_t	data_ready_queue;
 	unsigned long		flags;
 	u8			cntl_cache;
+	const char		*matrix[9];
 };
 
 /*

@@ -697,6 +698,28 @@ static int ak8975_read_raw(struct iio_dev *indio_dev,
 	return -EINVAL;
 }
 
+static ssize_t ak8975_show_matrix(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	const struct ak8975_data *data = iio_priv(dev_to_iio_dev(dev));
+	const char * const *m = data->matrix;
+
+	return sprintf(buf, "%s, %s, %s; %s, %s, %s; %s, %s, %s\n",
+		       m[0], m[1], m[2], m[3], m[4], m[5], m[6], m[7], m[8]);
+}
+
+static IIO_DEVICE_ATTR(in_magn_matrix, S_IRUGO, ak8975_show_matrix, NULL, -1);
+
+static struct attribute *ak8975_attrs[] = {
+	&iio_dev_attr_in_magn_matrix.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group ak8975_attrs_group = {
+	.attrs = ak8975_attrs
+};
+
 #define AK8975_CHANNEL(axis, index)					\
 	{								\
 		.type = IIO_MAGN,					\

@@ -716,6 +739,12 @@ static const struct iio_info ak8975_info = {
 	.driver_module = THIS_MODULE,
 };
 
+static const struct iio_info ak8975_matrix_info = {
+	.read_raw = &ak8975_read_raw,
+	.attrs = &ak8975_attrs_group,
+	.driver_module = THIS_MODULE,
+};
+
 static const struct acpi_device_id ak_acpi_match[] = {
 	{"AK8975", AK8975},
 	{"AK8963", AK8963},

@@ -785,6 +814,22 @@ static int ak8975_probe(struct i2c_client *client,
 	data->eoc_gpio = eoc_gpio;
 	data->eoc_irq = 0;
 
+	/*
+	 * Rotation matrix is expressed as an array of 3x3 strings to be able
+	 * to represent floating point numbers.
+	 */
+	err = of_property_read_string_array(client->dev.of_node, "matrix",
+					    data->matrix,
+					    ARRAY_SIZE(data->matrix));
+	if (err == ARRAY_SIZE(data->matrix))
+		indio_dev->info = &ak8975_matrix_info;
+	else if (err == -EINVAL)
+		indio_dev->info = &ak8975_info;
+	else if (err >= 0)
+		return -EINVAL;
+	else
+		return err;
+
 	/* id will be NULL when enumerated via ACPI */
 	if (id) {
 		chipset = (enum asahi_compass_chipset)(id->driver_data);

@@ -822,7 +867,6 @@ static int ak8975_probe(struct i2c_client *client,
 	indio_dev->dev.parent = &client->dev;
 	indio_dev->channels = ak8975_channels;
 	indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
-	indio_dev->info = &ak8975_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->name = name;
 	return devm_iio_device_register(&client->dev, indio_dev);

Quoted 15 lines · Gregor Boirie

Expose a rotation matrix to indicate userspace the chip placement with respect to the overall hardware system. This is needed to adjust coordinates sampled from a magnetometer chip when its position deviates from the main hardware system.

Final coordinates computation is delegated to userspace since:
* computation may involve floating point arithmetics ;
* it allows an application to combine adjustments with arbitrary transformations.

This 3 dimentional space rotation matrix is expressed as 3x3 array of strings to support floating point numbers. It may be retrieved from a "in_magn_matrix" sysfs attribute file. It is declared into ak8975 DTS entry as a "matrix" property.

Quoted 1 line

Signed-off-by Gregor Boirie <[email protected]>

This one definitely wants to go to the device tree list. I'd also like a few IIO related comments as well. I was sure we'd been through this before and ended up with some sort of solution, but now I can't find it... Oh well.

Definitely needs ABI docs in Documentation/ABI/testing/sysfs-bus-iio as well. We need the reference directions to be well specified as well - how do we define the main hardware orientation? on yours presumably the usual approach of using the screen is irrelevant so that definition could be a little 'interesting' to write down?

I'm also unsure of whether the right thing to do in the 'not provided' cases is to not export the setting, or to assume that the chip is at some 'standard' orientation and provide that?

Jonathan

Quoted 117 lines

---
  .../bindings/iio/magnetometer/ak8975.txt           | 10 +++++
  drivers/iio/magnetometer/ak8975.c                  | 46 +++++++++++++++++++++-
  2 files changed, 55 insertions(+), 1 deletion(-)

Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt +10 -0

index 34a3206..f936f86 100644
@@ -9,6 +9,7 @@ Optional properties:
 
    - gpios : should be device tree identifier of the magnetometer DRDY pin
    - vdd-supply: an optional regulator that needs to be on to provide VDD
+  - matrix: an optional 3x3 mounting rotation matrix
 
  Example:
 

@@ -17,4 +18,13 @@ ak8975@0c {
          reg = <0x0c>;
          gpios = <&gpj0 7 0>;
          vdd-supply = <&ldo_3v3_gnss>;
+        matrix = "-0.984807753012208",  /* x0 */
+                 "0",                   /* y0 */
+                 "-0.173648177666930",  /* z0 */
+                 "0",                   /* x1 */
+                 "-1",                  /* y1 */
+                 "0",                   /* z1 */
+                 "-0.173648177666930",  /* x2 */
+                 "0",                   /* y2 */
+                 "0.984807753012208";   /* z2 */
  };

drivers/iio/magnetometer/ak8975.c +45 -1

index 72c03d9..95c68952 100644
@@ -370,6 +370,7 @@ struct ak8975_data {
  	wait_queue_head_t	data_ready_queue;
  	unsigned long		flags;
  	u8			cntl_cache;
+	const char		*matrix[9];
  };
 
  /*

@@ -697,6 +698,28 @@ static int ak8975_read_raw(struct iio_dev *indio_dev,
  	return -EINVAL;
  }
 
+static ssize_t ak8975_show_matrix(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	const struct ak8975_data *data = iio_priv(dev_to_iio_dev(dev));
+	const char * const *m = data->matrix;
+
+	return sprintf(buf, "%s, %s, %s; %s, %s, %s; %s, %s, %s\n",
+		       m[0], m[1], m[2], m[3], m[4], m[5], m[6], m[7], m[8]);
+}
+
+static IIO_DEVICE_ATTR(in_magn_matrix, S_IRUGO, ak8975_show_matrix, NULL, -1);
+
+static struct attribute *ak8975_attrs[] = {
+	&iio_dev_attr_in_magn_matrix.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group ak8975_attrs_group = {
+	.attrs = ak8975_attrs
+};
+
  #define AK8975_CHANNEL(axis, index)					\
  	{								\
  		.type = IIO_MAGN,					\

@@ -716,6 +739,12 @@ static const struct iio_info ak8975_info = {
  	.driver_module = THIS_MODULE,
  };
 
+static const struct iio_info ak8975_matrix_info = {
+	.read_raw = &ak8975_read_raw,
+	.attrs = &ak8975_attrs_group,
+	.driver_module = THIS_MODULE,
+};
+
  static const struct acpi_device_id ak_acpi_match[] = {
  	{"AK8975", AK8975},
  	{"AK8963", AK8963},

@@ -785,6 +814,22 @@ static int ak8975_probe(struct i2c_client *client,
  	data->eoc_gpio = eoc_gpio;
  	data->eoc_irq = 0;
 
+	/*
+	 * Rotation matrix is expressed as an array of 3x3 strings to be able
+	 * to represent floating point numbers.
+	 */
+	err = of_property_read_string_array(client->dev.of_node, "matrix",
+					    data->matrix,
+					    ARRAY_SIZE(data->matrix));
+	if (err == ARRAY_SIZE(data->matrix))
+		indio_dev->info = &ak8975_matrix_info;
+	else if (err == -EINVAL)
+		indio_dev->info = &ak8975_info;
+	else if (err >= 0)
+		return -EINVAL;
+	else
+		return err;
+
  	/* id will be NULL when enumerated via ACPI */
  	if (id) {
  		chipset = (enum asahi_compass_chipset)(id->driver_data);

@@ -822,7 +867,6 @@ static int ak8975_probe(struct i2c_client *client,
  	indio_dev->dev.parent = &client->dev;
  	indio_dev->channels = ak8975_channels;
  	indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
-	indio_dev->info = &ak8975_info;
  	indio_dev->modes = INDIO_DIRECT_MODE;
  	indio_dev->name = name;
  	return devm_iio_device_register(&client->dev, indio_dev);

Quoted 16 lines · Jonathan Cameron

Quoted 15 lines · Gregor Boirie

Expose a rotation matrix to indicate userspace the chip placement with respect to the overall hardware system. This is needed to adjust coordinates sampled from a magnetometer chip when its position deviates from the main hardware system.

Final coordinates computation is delegated to userspace since:
* computation may involve floating point arithmetics ;
* it allows an application to combine adjustments with arbitrary transformations.

This 3 dimentional space rotation matrix is expressed as 3x3 array of strings to support floating point numbers. It may be retrieved from a "in_magn_matrix" sysfs attribute file. It is declared into ak8975 DTS entry as a "matrix" property.

Quoted 4 lines

Quoted 1 line

Signed-off-by Gregor Boirie <gregor.boirie-ITF29qwbsa/[email protected]>

This one definitely wants to go to the device tree list. I'd also like a few IIO related comments as well. I was sure we'd been through this before and ended up with some sort of solution, but now I can't find it... Oh well.

I took inv_mpu_core as an example. However matrices are exposed as integers and we really need floating point support.
A search on the device-tree mailing list archive does not show up with a solution to encode floating point numbers into DTS either.

Quoted 7 lines

Definitely needs ABI docs in Documentation/ABI/testing/sysfs-bus-iio as well. We need the reference directions to be well specified as well - how do we define the main hardware orientation? on yours presumably the usual approach of using the screen is irrelevant so that definition could be a little 'interesting' to write down?

The standard orientation for us is defined with respect to the drone's head and the propellers plane, which does not suit the nominal use cases indeed... Although it really deserves some more detailed documentation, I wonder if the question is relevant.
Given that the DTS is board specific (correct me if I'm wrong), why not consider the reference orientation as board specific as well (and make the whole thing implicit) ?

Quoted 5 lines

I'm also unsure of whether the right thing to do in the 'not provided' cases is to not export the setting, or to assume that the chip is at some 'standard' orientation and provide that?

As a self-explanatory interface, I suppose sysfs convention would expect to expose this even in the case of an identity matrix.
However, userspace would need to either:
* systematically apply rotation matrix ;
* or detect identity matrix and skip rotation which may require an a-priori knowledge of reference orientation (breaking the statement mentioned above).

Personally, I'd prefer not exporting the property at all when aligned with the main hardware orientation : this makes application simpler and allows for better performances.

What do you think ?
Grégor.

Quoted 113 lines

Jonathan

Quoted 110 lines

---
  .../bindings/iio/magnetometer/ak8975.txt           | 10 +++++
  drivers/iio/magnetometer/ak8975.c                  | 46 +++++++++++++++++++++-
  2 files changed, 55 insertions(+), 1 deletion(-)

Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt +1 -0

index 34a3206..f936f86 100644
@@ -9,6 +9,7 @@ Optional properties:
      - gpios : should be device tree identifier of the magnetometer DRDY pin
    - vdd-supply: an optional regulator that needs to be on to provide VDD
+  - matrix: an optional 3x3 mounting rotation matrix
    Example:
  @@ -17,4 +18,13 @@ ak8975@0c {
          reg = <0x0c>;
          gpios = <&gpj0 7 0>;

          vdd-supply = <&ldo_3v3_gnss>;

Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt +9 -0

+        matrix = "-0.984807753012208",  /* x0 */
+                 "0",                   /* y0 */
+                 "-0.173648177666930",  /* z0 */
+                 "0",                   /* x1 */
+                 "-1",                  /* y1 */
+                 "0",                   /* z1 */
+                 "-0.173648177666930",  /* x2 */
+                 "0",                   /* y2 */
+                 "0.984807753012208";   /* z2 */
  };

drivers/iio/magnetometer/ak8975.c +42 -1

index 72c03d9..95c68952 100644
@@ -370,6 +370,7 @@ struct ak8975_data {
      wait_queue_head_t    data_ready_queue;
      unsigned long        flags;
      u8            cntl_cache;
+    const char        *matrix[9];
  };
    /*

@@ -697,6 +698,28 @@ static int ak8975_read_raw(struct iio_dev *indio_dev,
      return -EINVAL;
  }
  +static ssize_t ak8975_show_matrix(struct device *dev,
+                  struct device_attribute *attr,
+                  char *buf)
+{
+    const struct ak8975_data *data = iio_priv(dev_to_iio_dev(dev));
+    const char * const *m = data->matrix;
+
+    return sprintf(buf, "%s, %s, %s; %s, %s, %s; %s, %s, %s\n",
+               m[0], m[1], m[2], m[3], m[4], m[5], m[6], m[7], m[8]);
+}
+
+static IIO_DEVICE_ATTR(in_magn_matrix, S_IRUGO, ak8975_show_matrix, NULL, -1);
+
+static struct attribute *ak8975_attrs[] = {
+    &iio_dev_attr_in_magn_matrix.dev_attr.attr,
+    NULL
+};
+
+static const struct attribute_group ak8975_attrs_group = {
+    .attrs = ak8975_attrs
+};
+
  #define AK8975_CHANNEL(axis, index)                    \
      {                                \
          .type = IIO_MAGN,                    \

@@ -716,6 +739,12 @@ static const struct iio_info ak8975_info = {
      .driver_module = THIS_MODULE,
  };
  +static const struct iio_info ak8975_matrix_info = {
+    .read_raw = &ak8975_read_raw,
+    .attrs = &ak8975_attrs_group,
+    .driver_module = THIS_MODULE,
+};
+
  static const struct acpi_device_id ak_acpi_match[] = {
      {"AK8975", AK8975},
      {"AK8963", AK8963},

@@ -785,6 +814,22 @@ static int ak8975_probe(struct i2c_client *client,
      data->eoc_gpio = eoc_gpio;
      data->eoc_irq = 0;
  +    /*
+     * Rotation matrix is expressed as an array of 3x3 strings to be able
+     * to represent floating point numbers.
+     */
+    err = of_property_read_string_array(client->dev.of_node, "matrix",
+                        data->matrix,
+                        ARRAY_SIZE(data->matrix));
+    if (err == ARRAY_SIZE(data->matrix))
+        indio_dev->info = &ak8975_matrix_info;
+    else if (err == -EINVAL)
+        indio_dev->info = &ak8975_info;
+    else if (err >= 0)
+        return -EINVAL;
+    else
+        return err;
+
      /* id will be NULL when enumerated via ACPI */
      if (id) {
          chipset = (enum asahi_compass_chipset)(id->driver_data);

@@ -822,7 +867,6 @@ static int ak8975_probe(struct i2c_client *client,
      indio_dev->dev.parent = &client->dev;
      indio_dev->channels = ak8975_channels;
      indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
-    indio_dev->info = &ak8975_info;
      indio_dev->modes = INDIO_DIRECT_MODE;
      indio_dev->name = name;
      return devm_iio_device_register(&client->dev, indio_dev);

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Quoted 18 lines · Gregor Boirie

Quoted 16 lines · Jonathan Cameron

Quoted 15 lines · Gregor Boirie

Expose a rotation matrix to indicate userspace the chip placement with respect to the overall hardware system. This is needed to adjust coordinates sampled from a magnetometer chip when its position deviates from the main hardware system.

Final coordinates computation is delegated to userspace since:
* computation may involve floating point arithmetics ;
* it allows an application to combine adjustments with arbitrary transformations.

This 3 dimentional space rotation matrix is expressed as 3x3 array of strings to support floating point numbers. It may be retrieved from a "in_magn_matrix" sysfs attribute file. It is declared into ak8975 DTS entry as a "matrix" property.

Quoted 8 lines

Quoted 4 lines

Quoted 1 line

Signed-off-by Gregor Boirie <gregor.boirie-ITF29qwbsa/[email protected]>

This one definitely wants to go to the device tree list. I'd also like a few IIO related comments as well. I was sure we'd been through this before and ended up with some sort of solution, but now I can't find it... Oh well.

I took inv_mpu_core as an example. However matrices are exposed as integers and we really need floating point support.
A search on the device-tree mailing list archive does not show up with a solution to encode floating point numbers into DTS either.

Certainly non obvious how to do this.

For anyone device tree related who picks this up (I've added a CC) we are basically talking about passing a rotation matrix from the device tree straight through to userspace to describe the relative orientation of some sensor. An array of strings clearly works, but is this the best way to do it?

Quoted 27 lines · Jonathan Cameron

Quoted 18 lines · Gregor Boirie

Quoted 16 lines · Jonathan Cameron

Quoted 15 lines · Gregor Boirie

Expose a rotation matrix to indicate userspace the chip placement with respect to the overall hardware system. This is needed to adjust coordinates sampled from a magnetometer chip when its position deviates from the main hardware system.

Final coordinates computation is delegated to userspace since:
* computation may involve floating point arithmetics ;
* it allows an application to combine adjustments with arbitrary transformations.

This 3 dimentional space rotation matrix is expressed as 3x3 array of strings to support floating point numbers. It may be retrieved from a "in_magn_matrix" sysfs attribute file. It is declared into ak8975 DTS entry as a "matrix" property.

Quoted 8 lines

Quoted 4 lines

Quoted 1 line

Signed-off-by Gregor Boirie <gregor.boirie-ITF29qwbsa/[email protected]>

This one definitely wants to go to the device tree list. I'd also like a few IIO related comments as well. I was sure we'd been through this before and ended up with some sort of solution, but now I can't find it... Oh well.

I took inv_mpu_core as an example. However matrices are exposed as integers and we really need floating point support.
A search on the device-tree mailing list archive does not show up with a solution to encode floating point numbers into DTS either.

Quoted 7 lines

Certainly non obvious how to do this.

For anyone device tree related who picks this up (I've added a CC) we are basically talking about passing a rotation matrix from the device tree straight through to userspace to describe the relative orientation of some sensor. An array of strings clearly works, but is this the best way to do it?

That's probably okay. I'd format the dts and sysfs to be arranged in a 3x3 matrix rather than a linear list though, but that is just style.

However, there's nothing really preventing us from having floats in DT. Data is not typed, so it would be a matter of adding the dtc parsing support. The other aspect would be the limited use of float types in the kernel (though that should not influence binding design). Are there cases of the kernel ABI using floats?

Rob
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Definitely needs ABI docs in Documentation/ABI/testing/sysfs-bus-iio as well. We need the reference directions to be well specified as well - how do we define the main hardware orientation? on yours presumably the usual approach of using the screen is irrelevant so that definition could be a little 'interesting' to write down?

Quoted 7 lines

The standard orientation for us is defined with respect to the drone's head and the propellers plane, which does not suit the nominal use cases indeed... Although it really deserves some more detailed documentation, I wonder if the question is relevant.
Given that the DTS is board specific (correct me if I'm wrong), why not consider the reference orientation as board specific as well (and make the whole thing implicit) ?

I think that is fine for your sort of usecase - though might be nice to keep a bit of documentation somewhere (perhaps as comments in the DTS), or perhaps more centrally - would be nice for userspace libraries if at least all aircraft had a similar 'default orientation'.

For the more 'standard' device with a screen I think we would want to standardise if at all possible. Most hand held devices have a 'natural' orientation (front facing camera at the top for example). In those cases we are basically looking at whether the sensor is mounted on the back or the front of the main circuit board and then of course it can be at any rotation in plane but typically is at 90 degrees (hence the inv mpu limitations)

I'm guessing there are existing userspace mappings for this. Perhaps in the Gnome sensors stuff?

Definitely needs ABI docs in Documentation/ABI/testing/sysfs-bus-iio as well. We need the reference directions to be well specified as well - how do we define the main hardware orientation? on yours presumably the usual approach of using the screen is irrelevant so that definition could be a little 'interesting' to write down?

Quoted 7 lines

The standard orientation for us is defined with respect to the drone's head and the propellers plane, which does not suit the nominal use cases indeed... Although it really deserves some more detailed documentation, I wonder if the question is relevant.
Given that the DTS is board specific (correct me if I'm wrong), why not consider the reference orientation as board specific as well (and make the whole thing implicit) ?

I think that is fine for your sort of usecase - though might be nice to keep a bit of documentation somewhere (perhaps as comments in the DTS), or perhaps more centrally - would be nice for userspace libraries if at least all aircraft had a similar 'default orientation'.

For the more 'standard' device with a screen I think we would want to standardise if at all possible. Most hand held devices have a 'natural' orientation (front facing camera at the top for example). In those cases we are basically looking at whether the sensor is mounted on the back or the front of the main circuit board and then of course it can be at any rotation in plane but typically is at 90 degrees (hence the inv mpu limitations)

I'm guessing there are existing userspace mappings for this. Perhaps in the Gnome sensors stuff?

On 03/09/2016 09:46 PM, Jonathan Cameron wrote:

[snip...]

Quoted 12 lines

Definitely needs ABI docs in Documentation/ABI/testing/sysfs-bus-iio as well. We need the reference directions to be well specified as well - how do we define the main hardware orientation? on yours presumably the usual approach of using the screen is irrelevant so that definition could be a little 'interesting' to write down?

Quoted 7 lines

The standard orientation for us is defined with respect to the drone's head and the propellers plane, which does not suit the nominal use cases indeed... Although it really deserves some more detailed documentation, I wonder if the question is relevant.
Given that the DTS is board specific (correct me if I'm wrong), why not consider the reference orientation as board specific as well (and make the whole thing implicit) ?

Quoted 4 lines

I think that is fine for your sort of usecase - though might be nice to keep a bit of documentation somewhere (perhaps as comments in the DTS), or perhaps more centrally - would be nice for userspace libraries if at least all aircraft had a similar 'default orientation'.

As you said earlier, things are never that simple. The standard orientation may vary with types of UAVs (quad-rotor, fixed wings, bizarre home made UFOs...)

Quoted 9 lines

For the more 'standard' device with a screen I think we would want to standardise if at all possible. Most hand held devices have a 'natural' orientation (front facing camera at the top for example). In those cases we are basically looking at whether the sensor is mounted on the back or the front of the main circuit board and then of course it can be at any rotation in plane but typically is at 90 degrees (hence the inv mpu limitations)

I'm guessing there are existing userspace mappings for this. Perhaps in the Gnome sensors stuff?

[snip...]

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Quoted 15 lines · Gregor Boirie

On 03/09/2016 09:46 PM, Jonathan Cameron wrote:

[snip...]

Quoted 12 lines

Definitely needs ABI docs in Documentation/ABI/testing/sysfs-bus-iio as well. We need the reference directions to be well specified as well - how do we define the main hardware orientation? on yours presumably the usual approach of using the screen is irrelevant so that definition could be a little 'interesting' to write down?

Quoted 7 lines

The standard orientation for us is defined with respect to the drone's head and the propellers plane, which does not suit the nominal use cases indeed... Although it really deserves some more detailed documentation, I wonder if the question is relevant.
Given that the DTS is board specific (correct me if I'm wrong), why not consider the reference orientation as board specific as well (and make the whole thing implicit) ?

Quoted 6 lines

Quoted 4 lines

I think that is fine for your sort of usecase - though might be nice to keep a bit of documentation somewhere (perhaps as comments in the DTS), or perhaps more centrally - would be nice for userspace libraries if at least all aircraft had a similar 'default orientation'.

As you said earlier, things are never that simple. The standard orientation may vary with types of UAVs (quad-rotor, fixed wings, bizarre home made UFOs...)

Sure, but let's document what we can so at least some cases are covered

This will be used together with an external trigger (e.g hrtimer based software trigger).

Signed-off-by Gregor Boirie <[email protected]>

---
 drivers/iio/magnetometer/Kconfig  |   2 +
 drivers/iio/magnetometer/ak8975.c | 150 +++++++++++++++++++++++++++++++-------
 2 files changed, 125 insertions(+), 27 deletions(-)

drivers/iio/magnetometer/Kconfig +2 -0

index 021dc53..d9834ed 100644
@@ -9,6 +9,8 @@ config AK8975
 	tristate "Asahi Kasei AK 3-Axis Magnetometer"
 	depends on I2C
 	depends on GPIOLIB || COMPILE_TEST
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Say yes here to build support for Asahi Kasei AK8975, AK8963,
 	  AK09911 or AK09912 3-Axis Magnetometer.

drivers/iio/magnetometer/ak8975.c +15 -17

index 95c68952..9559ab8 100644
@@ -36,6 +36,12 @@
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/regulator/consumer.h>
+
 /*
  * Register definitions, as well as various shifts and masks to get at the
  * individual fields of the registers.

@@ -617,22 +623,15 @@ static int wait_conversion_complete_interrupt(struct ak8975_data *data)
 	return ret > 0 ? 0 : -ETIME;
 }
 
-/*
- * Emits the raw flux value for the x, y, or z axis.
- */
-static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
+static int ak8975_start_read_axis(struct ak8975_data *data,
+				  const struct i2c_client *client)
 {
-	struct ak8975_data *data = iio_priv(indio_dev);
-	struct i2c_client *client = data->client;
-	int ret;
-
-	mutex_lock(&data->lock);
-
 	/* Set up the device for taking a sample. */
-	ret = ak8975_set_mode(data, MODE_ONCE);
-	if (ret < 0) {
+	int ret = ak8975_set_mode(data, MODE_ONCE);
+
+	if (ret) {
 		dev_err(&client->dev, "Error in setting operating mode\n");
-		goto exit;
+		return ret;
 	}
 
 	/* Wait for the conversion to complete. */

@@ -643,7 +642,7 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 	else
 		ret = wait_conversion_complete_polled(data);
 	if (ret < 0)
-		goto exit;
+		return ret;
 
 	/* This will be executed only for non-interrupt based waiting case */
 	if (ret & data->def->ctrl_masks[ST1_DRDY]) {

@@ -651,32 +650,46 @@ static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 					       data->def->ctrl_regs[ST2]);
 		if (ret < 0) {
 			dev_err(&client->dev, "Error in reading ST2\n");
-			goto exit;
+			return ret;
 		}
 		if (ret & (data->def->ctrl_masks[ST2_DERR] |
 			   data->def->ctrl_masks[ST2_HOFL])) {
 			dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
-			ret = -EINVAL;
-			goto exit;
+			return -EINVAL;
 		}
 	}
 

drivers/iio/magnetometer/ak8975.c +17 -2

+ */
+static int ak8975_read_axis(struct ak8975_data *data, int index, int *val)
+{
+	int ret;
+	const struct i2c_client *client = data->client;
+	const struct ak_def *def = data->def;
+
+	mutex_lock(&data->lock);
+
+	ret = ak8975_start_read_axis(data, client);
+	if (ret)
+		goto exit;
+
+	ret = i2c_smbus_read_word_data(client, def->data_regs[index]);
+	if (ret < 0)
 		goto exit;
-	}
 
 	mutex_unlock(&data->lock);
 
 	/* Clamp to valid range. */
-	*val = clamp_t(s16, ret, -data->def->range, data->def->range);
+	*val = clamp_t(s16, ret, -def->range, def->range);
 	return IIO_VAL_INT;
 
 exit:
 	mutex_unlock(&data->lock);
+	dev_err(&client->dev, "Error in reading axis\n");
 	return ret;
 }
 

drivers/iio/magnetometer/ak8975.c +1 -1

-		return ak8975_read_axis(indio_dev, chan->address, val);
+		return ak8975_read_axis(data, chan->address, val);
 	case IIO_CHAN_INFO_SCALE:
 		*val = 0;
 		*val2 = data->raw_to_gauss[chan->address];

drivers/iio/magnetometer/ak8975.c +29 -0

+	IIO_CHAN_SOFT_TIMESTAMP(3),
 };
 
+static const unsigned long ak8975_scan_masks[] = { 0x7, 0 };
+
 static const struct iio_info ak8975_info = {
 	.read_raw = &ak8975_read_raw,
 	.driver_module = THIS_MODULE,

@@ -768,6 +794,51 @@ static const char *ak8975_match_acpi_device(struct device *dev,
 	return dev_name(dev);
 }
 
+static irqreturn_t ak8975_handle_trigger(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct ak8975_data *data = iio_priv(indio_dev);
+	const struct i2c_client *client = data->client;
+	const struct ak_def *def = data->def;
+	int ret;
+	s16 buff[8]; /* 3 x 16 bits axis values + 1 aligned 64 bits timestamp */
+
+	mutex_lock(&data->lock);
+
+	ret = ak8975_start_read_axis(data, client);
+	if (ret)
+		goto unlock;
+
+	/*
+	 * For each axis, read the flux value from the appropriate register
+	 * (the register is specified in the iio device attributes).
+	 */
+	ret = i2c_smbus_read_i2c_block_data_or_emulated(client,
+							def->data_regs[0],
+							3 * sizeof(buff[0]),
+							(u8 *)buff);
+	if (ret < 0)
+		goto unlock;

drivers/iio/magnetometer/ak8975.c +11 -1

+
+unlock:
+	mutex_unlock(&data->lock);
+	dev_err(&client->dev, "Error in reading axes block\n");
+exit:
+	iio_trigger_notify_done(indio_dev->trig);
+	return IRQ_HANDLED;
+}
+
 static int ak8975_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {

@@ -867,9 +938,33 @@ static int ak8975_probe(struct i2c_client *client,
 	indio_dev->dev.parent = &client->dev;
 	indio_dev->channels = ak8975_channels;
 	indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
+	indio_dev->available_scan_masks = ak8975_scan_masks;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->name = name;
-	return devm_iio_device_register(&client->dev, indio_dev);
+

drivers/iio/magnetometer/ak8975.c +2 -0

+	return 0;
 }
 
 static const struct i2c_device_id ak8975_id[] = {

@@ -903,6 +998,7 @@ static struct i2c_driver ak8975_driver = {
 		.acpi_match_table = ACPI_PTR(ak_acpi_match),
 	},
 	.probe		= ak8975_probe,
+	.remove		= ak8975_remove,
 	.id_table	= ak8975_id,
 };
 module_i2c_driver(ak8975_driver);