iio: inv_mpu6050: Support i2c master and external readings

Using regmap_read_bulk is wrong because it assumes that a range of registers is being read. In our case reading from the fifo register will return multiple values but this is *not* auto-increment.

This currently works by accident.

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 33 ++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +29 -4

index d070062..8455af0 100644
@@ -21,6 +21,7 @@
 #include <linux/interrupt.h>
 #include <linux/kfifo.h>
 #include <linux/poll.h>
+#include <linux/spi/spi.h>
 #include "inv_mpu_iio.h"
 
 static void inv_clear_kfifo(struct inv_mpu6050_state *st)

@@ -128,6 +129,13 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 	u16 fifo_count;
 	s64 timestamp;
 
+	struct device *regmap_dev = regmap_get_device(st->map);
+	struct i2c_client *i2c;
+	struct spi_device *spi = NULL;
+
+	i2c = i2c_verify_client(regmap_dev);
+	spi = i2c ? NULL: to_spi_device(regmap_dev);
+
 	mutex_lock(&indio_dev->mlock);
 	if (!(st->chip_config.accl_fifo_enable |
 		st->chip_config.gyro_fifo_enable))

@@ -160,10 +168,27 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 	    fifo_count / bytes_per_datum + INV_MPU6050_TIME_STAMP_TOR)
 		goto flush_fifo;
 	while (fifo_count >= bytes_per_datum) {
-		result = regmap_bulk_read(st->map, st->reg->fifo_r_w,
-					  data, bytes_per_datum);
-		if (result)
-			goto flush_fifo;
+		/*
+		 * We need to do a large burst read from a single register.
+		 *
+		 * regmap_read_bulk assumes that multiple registers are
+		 * involved but in our case st->reg->fifo_r_w + 1 is something
+		 * completely unrelated.
+		 */
+		if (spi) {
+			u8 cmd = st->reg->fifo_r_w | 0x80;
+			result = spi_write_then_read(spi,
+					&cmd, 1,
+					data, bytes_per_datum);
+			if (result)
+				goto flush_fifo;
+		} else {
+			result = i2c_smbus_read_i2c_block_data(i2c,
+					st->reg->fifo_r_w,
+					bytes_per_datum, data);
+			if (result != bytes_per_datum)
+				goto flush_fifo;
+		}
 
 		result = kfifo_out(&st->timestamps, &timestamp, 1);
 		/* when there is no timestamp, put timestamp as 0 */

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 47 ++++++++++++++++++++++++++++++
 drivers/iio/imu/inv_mpu6050/inv_mpu_i2c.c  |  5 ----
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h  |  1 +
 drivers/iio/imu/inv_mpu6050/inv_mpu_spi.c  |  5 ----
 4 files changed, 48 insertions(+), 10 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +0 -0

index b269b37..5918c23 100644

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +41 -0

+       switch (reg) {
+       case INV_MPU6050_REG_TEMPERATURE:
+       case INV_MPU6050_REG_TEMPERATURE + 1:
+       case INV_MPU6050_REG_USER_CTRL:
+       case INV_MPU6050_REG_PWR_MGMT_1:
+       case INV_MPU6050_REG_FIFO_COUNT_H:
+       case INV_MPU6050_REG_FIFO_COUNT_H + 1:
+       case INV_MPU6050_REG_FIFO_R_W:
+               return true;
+       default:
+               return false;
+       }
+}
+
+static bool inv_mpu6050_precious_reg(struct device *dev, unsigned int reg)
+{
+       switch (reg) {
+       case INV_MPU6050_REG_FIFO_R_W:
+               return true;
+       default:
+               return false;
+       }
+}
+
+/*
+ * Common regmap config for inv_mpu devices
+ *
+ * The current volatile/precious registers are common among supported devices.
+ * When that changes the volatile/precious callbacks should go through the
+ * inv_mpu6050_reg_map structs.
+ */
+const struct regmap_config inv_mpu_regmap_config = {
+       .reg_bits = 8,
+       .val_bits = 8,
+
+       .cache_type = REGCACHE_RBTREE,
+       .volatile_reg = inv_mpu6050_volatile_reg,
+       .precious_reg = inv_mpu6050_precious_reg,
+};
+EXPORT_SYMBOL_GPL(inv_mpu_regmap_config);
+
 int inv_mpu6050_switch_engine(struct inv_mpu6050_state *st, bool en, u32 mask)
 {
        unsigned int d, mgmt_1;

drivers/iio/imu/inv_mpu6050/inv_mpu_i2c.c +0 -5

index 1a424a6..1a8d1a5 100644
@@ -20,11 +20,6 @@
 #include <linux/module.h>
 #include "inv_mpu_iio.h"
 
-static const struct regmap_config inv_mpu_regmap_config = {
-       .reg_bits = 8,
-       .val_bits = 8,
-};
-
 /*
  * The i2c read/write needs to happen in unlocked mode. As the parent
  * adapter is common. If we use locked versions, it will fail as

drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h +1 -0

index 47ca25b..297b0ef 100644
@@ -291,3 +291,4 @@ int inv_mpu_core_probe(struct regmap *regmap, int irq, const char *name,
 int inv_mpu_core_remove(struct device *dev);
 int inv_mpu6050_set_power_itg(struct inv_mpu6050_state *st, bool power_on);
 extern const struct dev_pm_ops inv_mpu_pmops;
+extern const struct regmap_config inv_mpu_regmap_config;

drivers/iio/imu/inv_mpu6050/inv_mpu_spi.c +0 -6

index 190a4a5..b3bd977 100644
@@ -17,11 +17,6 @@
 #include <linux/iio/iio.h>
 #include "inv_mpu_iio.h"
 
-static const struct regmap_config inv_mpu_regmap_config = {
-       .reg_bits = 8,
-       .val_bits = 8,
-};
-
 static int inv_mpu_i2c_disable(struct iio_dev *indio_dev)
 {
        struct inv_mpu6050_state *st = iio_priv(indio_dev);
--

2.5.5

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Quoted 16 lines · Crestez Dan Leonard

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 47 ++++++++++++++++++++++++++++++
 drivers/iio/imu/inv_mpu6050/inv_mpu_i2c.c  |  5 ----
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h  |  1 +
 drivers/iio/imu/inv_mpu6050/inv_mpu_spi.c  |  5 ----
 4 files changed, 48 insertions(+), 10 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +0 -0

index b269b37..5918c23 100644
@@ -116,6 +116,53 @@ static const struct inv_mpu6050_hw hw_info[] = {
        },
 };
 

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c static const struct inv_mpu6050_hw hw_info[] = { · line 124

Quoted 6 lines

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +6 -0

+static bool inv_mpu6050_volatile_reg(struct device *dev, unsigned int reg)
+{
+       if (reg >= INV_MPU6050_REG_RAW_ACCEL && reg < INV_MPU6050_REG_RAW_ACCEL + 6)
+               return true;
+       if (reg >= INV_MPU6050_REG_RAW_GYRO && reg < INV_MPU6050_REG_RAW_GYRO + 6)
+               return true;

I think you want to put parenthesis around the addition operations...

the condition check probably don't evaluate to what you are expecting.

Quoted 5 lines

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +5 -0

+       switch (reg) {
+       case INV_MPU6050_REG_TEMPERATURE:
+       case INV_MPU6050_REG_TEMPERATURE + 1:
+       case INV_MPU6050_REG_USER_CTRL:
+       case INV_MPU6050_REG_PWR_MGMT_1:

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c static const struct inv_mpu6050_hw hw_info[] = { · line 137

Quoted 8 lines

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +8 -0

+       case INV_MPU6050_REG_FIFO_COUNT_H:
+       case INV_MPU6050_REG_FIFO_COUNT_H + 1:
+       case INV_MPU6050_REG_FIFO_R_W:
+               return true;
+       default:
+               return false;
+       }
+}

Quoted 18 lines · Matt Ranostay

Quoted 16 lines · Crestez Dan Leonard

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 47 ++++++++++++++++++++++++++++++
 drivers/iio/imu/inv_mpu6050/inv_mpu_i2c.c  |  5 ----
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h  |  1 +
 drivers/iio/imu/inv_mpu6050/inv_mpu_spi.c  |  5 ----
 4 files changed, 48 insertions(+), 10 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +0 -0

index b269b37..5918c23 100644
@@ -116,6 +116,53 @@ static const struct inv_mpu6050_hw hw_info[] = {
        },
 };
 

Quoted 8 lines

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c static const struct inv_mpu6050_hw hw_info[] = { · line 124

Quoted 6 lines

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +6 -0

+static bool inv_mpu6050_volatile_reg(struct device *dev, unsigned int reg)
+{
+       if (reg >= INV_MPU6050_REG_RAW_ACCEL && reg < INV_MPU6050_REG_RAW_ACCEL + 6)
+               return true;
+       if (reg >= INV_MPU6050_REG_RAW_GYRO && reg < INV_MPU6050_REG_RAW_GYRO + 6)
+               return true;

I think you want to put parenthesis around the addition operations...

Maybe.

Quoted 1 line

the condition check probably don't evaluate to what you are expecting.

Looks sane to me since + has highest precedence, then < and >=, and && comes in last...

...but even so, I think I would use an ellipsis in the switch statement instead, like so:

static bool inv_mpu6050_volatile_reg(struct device *dev, unsigned int reg)

{
	switch (reg) {
	case INV_MPU6050_REG_RAW_ACCEL ... INV_MPU6050_REG_RAW_ACCEL + 5:
	case INV_MPU6050_REG_RAW_GYRO ... INV_MPU6050_REG_RAW_GYRO  + 5:
	case INV_MPU6050_REG_TEMPERATURE:
	case INV_MPU6050_REG_TEMPERATURE + 1:
	case INV_MPU6050_REG_USER_CTRL:
	case INV_MPU6050_REG_PWR_MGMT_1:
	case INV_MPU6050_REG_FIFO_COUNT_H:
	case INV_MPU6050_REG_FIFO_COUNT_H + 1:
	case INV_MPU6050_REG_FIFO_R_W:
		return true;
	default:
		return false;
	}
}

Quoted 39 lines · Peter Rosin

Quoted 18 lines · Matt Ranostay

Quoted 16 lines · Crestez Dan Leonard

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 47 ++++++++++++++++++++++++++++++
 drivers/iio/imu/inv_mpu6050/inv_mpu_i2c.c  |  5 ----
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h  |  1 +
 drivers/iio/imu/inv_mpu6050/inv_mpu_spi.c  |  5 ----
 4 files changed, 48 insertions(+), 10 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +0 -0

index b269b37..5918c23 100644
@@ -116,6 +116,53 @@ static const struct inv_mpu6050_hw hw_info[] = {
        },
 };
 

Quoted 8 lines

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c static const struct inv_mpu6050_hw hw_info[] = { · line 124

Quoted 6 lines

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +6 -0

+static bool inv_mpu6050_volatile_reg(struct device *dev, unsigned int reg)
+{
+       if (reg >= INV_MPU6050_REG_RAW_ACCEL && reg < INV_MPU6050_REG_RAW_ACCEL + 6)
+               return true;
+       if (reg >= INV_MPU6050_REG_RAW_GYRO && reg < INV_MPU6050_REG_RAW_GYRO + 6)
+               return true;

I think you want to put parenthesis around the addition operations...

Maybe.

Quoted 1 line

the condition check probably don't evaluate to what you are expecting.

Looks sane to me since + has highest precedence, then < and >=, and && comes in last...

...but even so, I think I would use an ellipsis in the switch statement instead, like so:

static bool inv_mpu6050_volatile_reg(struct device *dev, unsigned int reg)

Quoted 16 lines

{
	switch (reg) {
	case INV_MPU6050_REG_RAW_ACCEL ... INV_MPU6050_REG_RAW_ACCEL + 5:
	case INV_MPU6050_REG_RAW_GYRO ... INV_MPU6050_REG_RAW_GYRO  + 5:
	case INV_MPU6050_REG_TEMPERATURE:
	case INV_MPU6050_REG_TEMPERATURE + 1:
	case INV_MPU6050_REG_USER_CTRL:
	case INV_MPU6050_REG_PWR_MGMT_1:
	case INV_MPU6050_REG_FIFO_COUNT_H:
	case INV_MPU6050_REG_FIFO_COUNT_H + 1:
	case INV_MPU6050_REG_FIFO_R_W:
		return true;
	default:
		return false;
	}
}

Neat, I didn't know about this extension. It does look nicer in this function.

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c    | 13 ++++++++-----
 drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c |  3 ++-
 2 files changed, 10 insertions(+), 6 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +8 -5

index 8455af0..3fc0b71 100644
@@ -41,7 +41,8 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 	struct inv_mpu6050_state  *st = iio_priv(indio_dev);
 
 	/* disable interrupt */
-	result = regmap_write(st->map, st->reg->int_enable, 0);
+	result = regmap_update_bits(st->map, st->reg->int_enable,
+				    INV_MPU6050_BIT_DATA_RDY_EN, 0);
 	if (result) {
 		dev_err(regmap_get_device(st->map), "int_enable failed %d\n",
 			result);

@@ -68,8 +69,9 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 	/* enable interrupt */
 	if (st->chip_config.accl_fifo_enable ||
 	    st->chip_config.gyro_fifo_enable) {
-		result = regmap_write(st->map, st->reg->int_enable,
-				      INV_MPU6050_BIT_DATA_RDY_EN);
+		result = regmap_update_bits(st->map, st->reg->int_enable,
+					    INV_MPU6050_BIT_DATA_RDY_EN,
+					    INV_MPU6050_BIT_DATA_RDY_EN);
 		if (result)
 			return result;
 	}

@@ -92,8 +94,9 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 
 reset_fifo_fail:
 	dev_err(regmap_get_device(st->map), "reset fifo failed %d\n", result);
-	result = regmap_write(st->map, st->reg->int_enable,
-			      INV_MPU6050_BIT_DATA_RDY_EN);
+	result = regmap_update_bits(st->map, st->reg->int_enable,
+				    INV_MPU6050_BIT_DATA_RDY_EN,
+				    INV_MPU6050_BIT_DATA_RDY_EN);
 
 	return result;
 }

drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c +2 -1

index e8818d4..1a6bad3 100644
@@ -69,7 +69,8 @@ static int inv_mpu6050_set_enable(struct iio_dev *indio_dev, bool enable)
 		if (result)
 			return result;
 
-		result = regmap_write(st->map, st->reg->int_enable, 0);
+		result = regmap_update_bits(st->map, st->reg->int_enable,
+					INV_MPU6050_BIT_DATA_RDY_EN, 0);
 		if (result)
 			return result;
 

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h     | 2 ++
 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c    | 9 ++++++---
 drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c | 4 +++-
 3 files changed, 11 insertions(+), 4 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h +2 -0

index 297b0ef..bd2c0fd 100644
@@ -80,6 +80,7 @@ enum inv_devices {
  *  @enable:		master enable state.
  *  @accl_fifo_enable:	enable accel data output
  *  @gyro_fifo_enable:	enable gyro data output
+ *  @user_ctrl:		The non-volatile bits of user_ctrl
  *  @fifo_rate:		FIFO update rate.
  */
 struct inv_mpu6050_chip_config {

@@ -89,6 +90,7 @@ struct inv_mpu6050_chip_config {
 	unsigned int enable:1;
 	unsigned int accl_fifo_enable:1;
 	unsigned int gyro_fifo_enable:1;
+	u8 user_ctrl;
 	u16 fifo_rate;
 };
 

drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +6 -3

index 3fc0b71..56ee1e2 100644
@@ -53,13 +53,15 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 	if (result)
 		goto reset_fifo_fail;
 	/* disable fifo reading */
-	result = regmap_write(st->map, st->reg->user_ctrl, 0);
+	st->chip_config.user_ctrl &= ~INV_MPU6050_BIT_FIFO_EN;
+	result = regmap_write(st->map, st->reg->user_ctrl,
+			      st->chip_config.user_ctrl);
 	if (result)
 		goto reset_fifo_fail;
 
 	/* reset FIFO*/
 	result = regmap_write(st->map, st->reg->user_ctrl,
-			      INV_MPU6050_BIT_FIFO_RST);
+			      st->chip_config.user_ctrl | INV_MPU6050_BIT_FIFO_RST);
 	if (result)
 		goto reset_fifo_fail;
 

@@ -76,8 +78,9 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 			return result;
 	}
 	/* enable FIFO reading and I2C master interface*/
+	st->chip_config.user_ctrl |= INV_MPU6050_BIT_FIFO_EN;
 	result = regmap_write(st->map, st->reg->user_ctrl,
-			      INV_MPU6050_BIT_FIFO_EN);
+			      st->chip_config.user_ctrl);
 	if (result)
 		goto reset_fifo_fail;
 	/* enable sensor output to FIFO */

drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c +3 -1

index 1a6bad3..fc55923 100644
@@ -74,7 +74,9 @@ static int inv_mpu6050_set_enable(struct iio_dev *indio_dev, bool enable)
 		if (result)
 			return result;
 
-		result = regmap_write(st->map, st->reg->user_ctrl, 0);
+		st->chip_config.user_ctrl &= ~INV_MPU6050_BIT_FIFO_EN;
+		result = regmap_write(st->map, st->reg->user_ctrl,
+				      st->chip_config.user_ctrl);
 		if (result)
 			return result;
 

The MPU has an auxiliary I2C bus for connecting external sensors. This bus has two operating modes:
* bypasss: which connects the primary and auxiliary busses together. This is already supported via an i2c mux.
* master: where the MPU acts as a master to any external connected sensors. This is implemented by this patch.

This I2C master mode also works when the MPU itself is connected via SPI.

I2C master supports up to 5 slaves. Slaves 0-3 have a common operating mode while slave 4 is different. This patch implements an i2c adapter using slave 4.

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 .../devicetree/bindings/iio/imu/inv_mpu6050.txt    |  66 +++++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c         | 258 ++++++++++++++++++++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h          |  36 +++
 drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c      |   8 -
 4 files changed, 355 insertions(+), 13 deletions(-)

Documentation/devicetree/bindings/iio/imu/inv_mpu6050.txt +5 -4

index a9fc11e..778d076 100644
@@ -1,16 +1,31 @@
 InvenSense MPU-6050 Six-Axis (Gyro + Accelerometer) MEMS MotionTracking Device
 
-http://www.invensense.com/mems/gyro/mpu6050.html
-
 Required properties:
- - compatible : should be "invensense,mpu6050"
- - reg : the I2C address of the sensor
+ - compatible : one of "invensense,mpu6000", "invensense,mpu6050",
+	"invensense,mpu6000" or "invensense,mpu9150"
+ - reg : the I2C or SPI address of the sensor
  - interrupt-parent : should be the phandle for the interrupt controller
  - interrupts : interrupt mapping for GPIO IRQ
 
 Optional properties:
  - mount-matrix: an optional 3x3 mounting rotation matrix
+ - invensense,i2c-aux-master: operate aux i2c in "master" mode (default is bypass).
+

Right now it is possible to only enable some of the x/y/z channels, for example you can enable accel_z without x or y but if you actually do that what you get is actually only the x channel.

Fix this by reformatting the hardware sample to only include the requested channels.

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h  |   8 +++
 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 107 ++++++++++++++++++++++++++++-
 2 files changed, 112 insertions(+), 3 deletions(-)

drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h +8 -0

index 85f9b50..ec1401d 100644
@@ -152,6 +152,11 @@ struct inv_mpu6050_state {
 	/* Value of I2C_MST_STATUS after slv4_done */
 	u8 slv4_done_status;
 #endif
+
+#define INV_MPU6050_MAX_SCAN_ELEMENTS 7
+	unsigned int scan_offsets[INV_MPU6050_MAX_SCAN_ELEMENTS];
+	unsigned int scan_lengths[INV_MPU6050_MAX_SCAN_ELEMENTS];
+	bool realign_required;
 };
 
 /*register and associated bit definition*/

@@ -274,6 +279,9 @@ enum inv_mpu6050_scan {
 	INV_MPU6050_SCAN_TIMESTAMP,
 };
 
+#define INV_MPU6050_SCAN_MASK_ACCEL    0x07
+#define INV_MPU6050_SCAN_MASK_GYRO     0x38
+
 enum inv_mpu6050_filter_e {
 	INV_MPU6050_FILTER_256HZ_NOLPF2 = 0,
 	INV_MPU6050_FILTER_188HZ,

drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +73 -0

index 56ee1e2..49e503c 100644
@@ -24,6 +24,90 @@
 #include <linux/spi/spi.h>
 #include "inv_mpu_iio.h"
 
+static void inv_mpu_get_scan_offsets(
+		struct iio_dev *indio_dev,
+		const unsigned long *mask,
+		const unsigned int masklen,
+		unsigned int *scan_offsets)
+{
+	unsigned int pos = 0;
+
+	if (*mask & INV_MPU6050_SCAN_MASK_ACCEL) {
+		scan_offsets[INV_MPU6050_SCAN_ACCL_X] = pos + 0;
+		scan_offsets[INV_MPU6050_SCAN_ACCL_Y] = pos + 2;
+		scan_offsets[INV_MPU6050_SCAN_ACCL_Z] = pos + 4;
+		pos += 6;
+	}
+	if (*mask & INV_MPU6050_SCAN_MASK_GYRO) {
+		scan_offsets[INV_MPU6050_SCAN_GYRO_X] = pos + 0;
+		scan_offsets[INV_MPU6050_SCAN_GYRO_Y] = pos + 2;
+		scan_offsets[INV_MPU6050_SCAN_GYRO_Z] = pos + 4;
+		pos += 6;
+	}
+}
+
+/* This is slowish but relatively common */
+static const struct iio_chan_spec *
+iio_chan_by_scan_index(struct iio_dev *indio_dev, int index)
+{
+	int i;
+
+	for (i = 0; i < indio_dev->num_channels; ++i)
+		if (indio_dev->channels[i].scan_index == index)
+			return &indio_dev->channels[i];
+
+	return NULL;
+}
+
+static int iio_check_scan_offsets_aligned(
+		struct iio_dev *indio_dev,
+		const unsigned long *mask,
+		unsigned int masklen,
+		unsigned int *scan_offsets)
+{
+	int scan_index;
+	unsigned int pos = 0;
+	const struct iio_chan_spec *chan;
+
+	for_each_set_bit(scan_index, mask, masklen) {
+		chan = iio_chan_by_scan_index(indio_dev, scan_index);
+		if (scan_offsets[scan_index] != pos)
+			return false;
+		pos = ALIGN(pos + chan->scan_type.storagebits / 8,
+			    chan->scan_type.storagebits / 8);
+	}
+
+	return true;
+}
+
+static void iio_get_scan_lengths(struct iio_dev *indio_dev, unsigned int *scan_length)
+{
+	int i;
+	const struct iio_chan_spec *chan;
+
+	for (i = 0; i < indio_dev->num_channels; ++i) {
+		chan = &indio_dev->channels[i];
+		if (chan->scan_index < 0)
+			continue;
+		scan_length[chan->scan_index] = chan->scan_type.storagebits / 8;
+	}
+}
+
+static void iio_realign_sample(
+		struct iio_dev *indio_dev,
+		const u8 *ibuf, u8 *obuf,
+		const unsigned int *scan_offset,

drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +21 -3

+
 static void inv_clear_kfifo(struct inv_mpu6050_state *st)
 {
 	unsigned long flags;

@@ -38,7 +122,9 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 {
 	int result;
 	u8 d;
-	struct inv_mpu6050_state  *st = iio_priv(indio_dev);
+	struct inv_mpu6050_state *st = iio_priv(indio_dev);
+	const unsigned long *mask = indio_dev->active_scan_mask;
+	unsigned int masklen = indio_dev->masklength;
 
 	/* disable interrupt */
 	result = regmap_update_bits(st->map, st->reg->int_enable,

@@ -93,6 +179,13 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 	if (result)
 		goto reset_fifo_fail;
 
+	/* check realign required */
+	inv_mpu_get_scan_offsets(indio_dev, mask, masklen, st->scan_offsets);
+	st->realign_required = !iio_check_scan_offsets_aligned(
+			indio_dev, mask, masklen, st->scan_offsets);
+	if (st->realign_required)
+		iio_get_scan_lengths(indio_dev, st->scan_lengths);
+
 	return 0;
 
 reset_fifo_fail:

@@ -201,8 +294,16 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 		if (result == 0)
 			timestamp = 0;
 
-		result = iio_push_to_buffers_with_timestamp(indio_dev, data,
-							    timestamp);
+		if (st->realign_required) {
+			u8 adata[INV_MPU6050_OUTPUT_DATA_SIZE];
+			iio_realign_sample(indio_dev, data, adata,
+					    st->scan_offsets, st->scan_lengths);
+			result = iio_push_to_buffers_with_timestamp(
+					indio_dev, adata, timestamp);
+		} else {
+			result = iio_push_to_buffers_with_timestamp(
+					indio_dev, data, timestamp);
+		}
 		if (result)
 			goto flush_fifo;
 		fifo_count -= bytes_per_datum;

Quoted 6 lines · Crestez Dan Leonard

Right now it is possible to only enable some of the x/y/z channels, for example you can enable accel_z without x or y but if you actually do that what you get is actually only the x channel.

Fix this by reformatting the hardware sample to only include the requested channels.

As it stands here there is no benefit in doing this over using the core demux. In fact it's considerably less efficient (fair enough that you are keeping it simple in the first instance).
The patch description should make that clear.

I'd definitely like to see simple extension of that option to handle a callback to get the nearest scanmask that is possible (as an alternative to the static scan_masks_available list.)

This only gets interesting if we are dealing with the unaligned case and for these parts that only kicks in I think if the slave devices have say 3 bytes in their data type.

Quoted 2 lines · Jonathan Cameron

Quoted 1 line · Crestez Dan Leonard

Right now it is possible to only enable some of the x/y/z channels,

for

Quoted 5 lines

Quoted 5 lines

example you can enable accel_z without x or y but if you actually do that what you get is actually only the x channel.

Fix this by reformatting the hardware sample to only include the requested channels.

Quoted 1 line

As it stands here there is no benefit in doing this over using the

core

Quoted 3 lines

demux. In fact it's considerably less efficient (fair enough that you are keeping it simple in the first instance).
The patch description should make that clear.

Why is it less efficient? All it really does is a bunch of memcpy.

Quoted 3 lines

I'd definitely like to see simple extension of that option to handle a callback to get the nearest scanmask that is possible (as an

alternative

Quoted 3 lines

to the static scan_masks_available list.)

This only gets interesting if we are dealing with the unaligned case

and for

Quoted 1 line

these parts that only kicks in I think if the slave devices have say

3 bytes in

Quoted 1 line

their data type.

But I want to deal with the unaligned case because it's better than introducing odd validations on slave channels. If I added an extension to get the nearest scanmask I would have to remove it in PATCH 7.

Quoted 11 lines · Crestez Dan Leonard

Quoted 2 lines · Jonathan Cameron

Quoted 1 line · Crestez Dan Leonard

Right now it is possible to only enable some of the x/y/z channels,

for

Quoted 6 lines

Quoted 5 lines

example you can enable accel_z without x or y but if you actually do that what you get is actually only the x channel.

Fix this by reformatting the hardware sample to only include the requested channels.

As it stands here there is no benefit in doing this over using the

core

Quoted 5 lines

Quoted 3 lines

demux. In fact it's considerably less efficient (fair enough that you are keeping it simple in the first instance).
The patch description should make that clear.

Why is it less efficient? All it really does is a bunch of memcpy.

Not doing agglomeration of neighbouring copies (iirc) not git either set of code to hand!

Quoted 8 lines

Quoted 2 lines

I'd definitely like to see simple extension of that option to handle a callback to get the nearest scanmask that is possible (as an

alternative

Quoted 3 lines

to the static scan_masks_available list.)

This only gets interesting if we are dealing with the unaligned case

and for

Quoted 1 line

these parts that only kicks in I think if the slave devices have say

Quoted 6 lines

3 bytes in

Quoted 1 line

their data type.

But I want to deal with the unaligned case because it's better than introducing odd validations on slave channels. If I added an extension to get the nearest scanmask I would have to remove it in PATCH 7.

Hmm I must have misread that. Though you were only supporting 16 bit channels
for aux sensors.

Then for now can we give this a slightly less generic name. I am not happy
enough that we want this in the core 'yet'.
Easy to rename later if it makes sense.

Quoted 1 line · Jonathan Cameron

On 30 May 2016 14:44:41 BST, Crestez Dan Leonard

Quoted 3 lines · <[email protected]> wrote:

Quoted 3 lines · Jonathan Cameron

Quoted 2 lines · Crestez Dan Leonard

Quoted 1 line

Right now it is possible to only enable some of the x/y/z

channels,

Quoted 2 lines

Quoted 2 lines

for

Quoted 1 line

Quoted 1 line

example you can enable accel_z without x or y but if you actually

do

Quoted 7 lines

Quoted 7 lines

Quoted 5 lines

Quoted 4 lines

that what you get is actually only the x channel.

Fix this by reformatting the hardware sample to only include the requested channels.

As it stands here there is no benefit in doing this over using the

core

Quoted 1 line

demux. In fact it's considerably less efficient (fair enough that

you

Quoted 6 lines

Quoted 4 lines

Quoted 2 lines

are keeping it simple in the first instance).
The patch description should make that clear.

Why is it less efficient? All it really does is a bunch of memcpy.

Not doing agglomeration of neighbouring copies (iirc) not git either

set of code to

Quoted 1 line

hand!

You're right about that. But the total data rate is still very low.

Quoted 1 line

Quoted 1 line

Quoted 1 line

I'd definitely like to see simple extension of that option to

handle

Quoted 5 lines

Quoted 5 lines

Quoted 1 line

a callback to get the nearest scanmask that is possible (as an

alternative

Quoted 3 lines

to the static scan_masks_available list.)

This only gets interesting if we are dealing with the unaligned

case

Quoted 2 lines

Quoted 2 lines

and for

Quoted 1 line

these parts that only kicks in I think if the slave devices have

say

Quoted 5 lines

Quoted 5 lines

3 bytes in

Quoted 1 line

their data type.

But I want to deal with the unaligned case because it's better than introducing odd validations on slave channels. If I added an

extension

Quoted 2 lines

Quoted 1 line

to get the nearest scanmask I would have to remove it in PATCH 7.

Hmm I must have misread that. Though you were only supporting 16 bit

channels

Quoted 1 line

for aux sensors.

That was in a previous version, I dropped that limitation now.

Quoted 1 line

Then for now can we give this a slightly less generic name. I am not

happy

Quoted 2 lines

enough that we want this in the core 'yet'.
Easy to rename later if it makes sense.

Ok, I will rename these functions to start with inv_mpu_* instead of iio_*.

In theory it would be interesting to refactor the iio demuxing code to support this but then this patch serios would grow even more complicated.

This works by copying the iio_chan_specs from the slave device and republishing them as if they belonged to the MPU itself. All read/write_raw operations are forwarded to the other driver.

The original device is still registered with linux as a normal driver and works normally and you can poke at it to configure stuff like sample rates and scaling factors.

Buffer values are read from the MPU fifo, allowing a much higher sampling rate.

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 .../devicetree/bindings/iio/imu/inv_mpu6050.txt    |  47 ++-

This works by copying the iio_chan_specs from the slave device and republishing them as if they belonged to the MPU itself. All read/write_raw operations are forwarded to the other driver.

The original device is still registered with linux as a normal driver and works normally and you can poke at it to configure stuff like sample rates and scaling factors.

Buffer values are read from the MPU fifo, allowing a much higher sampling rate.

Signed-off-by Crestez Dan Leonard <[email protected]>

---
 .../devicetree/bindings/iio/imu/inv_mpu6050.txt    |  47 ++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c         | 387 ++++++++++++++++++++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h          |  74 +++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c         |  65 +++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c      |   9 +
 5 files changed, 556 insertions(+), 26 deletions(-)

Documentation/devicetree/bindings/iio/imu/inv_mpu6050.txt +17 -3

index 778d076..07d572a 100644
@@ -11,8 +11,8 @@ Optional properties:
  - mount-matrix: an optional 3x3 mounting rotation matrix
  - invensense,i2c-aux-master: operate aux i2c in "master" mode (default is bypass).
 
-The MPU has an auxiliary i2c bus for additional sensors. Devices attached this
-way can be described as for a regular linux i2c bus.
+It is possible to attach auxiliary sensors to the MPU and have them be handled
+by linux. Those auxiliary sensors are described as an i2c bus.
 
 It is possible to interact with aux devices in "bypass" or "master" mode. In
 "bypass" mode the auxiliary SDA/SCL lines are connected directly to the main i2c

@@ -25,7 +25,31 @@ In "master" mode aux devices are listed behind a "i2c@1" node with reg = <1>;
 The master and bypass modes are not supported at the same time. The
 "invensense,i2c-aux-master" property must be set to activate master mode.
 Bypass mode is generally faster but master mode also works when the MPU is
-connected via SPI.
+connected via SPI. Enabling master mode is required for automated external
+readings.
+
+
+It is possible to configure the MPU to automatically fetch reading for
+devices connected on the auxiliary i2c bus without CPU intervention. When this
+is done the driver will present the channels of the slaved devices as if they
+belong to the MPU device itself.
+
+Reads and write to config values (like scaling factors) are forwarded to the
+other driver while data reads are handled from MPU registers. The channels are
+also available through the MPU's iio triggered buffer mechanism. This feature
+can allow sampling up to 24 bytes from 4 slaves at a much higher rate.
+
+This is specified in device tree as an "invensense,external-sensors" node with

Documentation/devicetree/bindings/iio/imu/inv_mpu6050.txt +16 -1

 Example:
 	mpu6050@68 {

@@ -65,7 +89,8 @@ Example describing mpu9150 (which includes an ak9875 on chip):
 		};
 	};
 
-Example describing a mpu6500 via SPI with an hmc5883l on auxiliary i2c:
+Example describing a mpu6500 via SPI with an hmc5883l on aux i2c configured for
+automatic external readings as slave 0:
 	mpu6500@0 {
 		compatible = "invensense,mpu6500";
 		reg = <0x0>;

@@ -73,6 +98,8 @@ Example describing a mpu6500 via SPI with an hmc5883l on auxiliary i2c:
 		interrupt-parent = <&gpio1>;
 		interrupts = <31 1>;
 
+		invensense,i2c-aux-master;
+
 		#address-cells = <1>;
 		#size-cells = <0>;
 		i2c@1 {

@@ -85,4 +112,16 @@ Example describing a mpu6500 via SPI with an hmc5883l on auxiliary i2c:
 				reg = <0x1e>;
 			};
 		};
+
+		invensense,external-sensors {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			hmc5833l@0 {
+				reg = <0>;
+				invensense,addr = <0x1e>;
+				invensense,reg = <3>;
+				invensense,len = <6>;
+				invensense,external-channels = <0 1 2>;
+			};
+		};
 	};

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +3 -0

index 76683b8..715b2e4 100644
@@ -126,6 +126,9 @@ static bool inv_mpu6050_volatile_reg(struct device *dev, unsigned int reg)
 		return true;
 	if (reg >= INV_MPU6050_REG_RAW_GYRO && reg < INV_MPU6050_REG_RAW_GYRO + 6)
 		return true;
+	if (reg < INV_MPU6050_REG_EXT_SENS_DATA_00 + INV_MPU6050_CNT_EXT_SENS_DATA &&
+			reg >= INV_MPU6050_REG_EXT_SENS_DATA_00)
+		return true;
 	switch (reg) {
 	case INV_MPU6050_REG_TEMPERATURE:
 	case INV_MPU6050_REG_TEMPERATURE + 1:

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +379 -3

 	int ret = 0;
+	int chan_index;
+
+	if (chan > indio_dev->channels + indio_dev->num_channels ||
+			chan < indio_dev->channels)
+		return -EINVAL;
+	chan_index = chan - indio_dev->channels;
+	if (chan_index >= INV_MPU6050_NUM_INT_CHAN) {
+		struct inv_mpu_ext_chan_state *ext_chan_state =
+				&st->ext_chan[chan_index - INV_MPU6050_NUM_INT_CHAN];
+		struct inv_mpu_ext_sens_state *ext_sens_state =
+				&st->ext_sens[ext_chan_state->ext_sens_index];
+		struct iio_dev *orig_dev = ext_sens_state->orig_dev;
+		const struct iio_chan_spec *orig_chan =
+				&orig_dev->channels[ext_chan_state->orig_chan_index];
+		return orig_dev->info->read_raw(orig_dev, orig_chan, val, val2, mask);
+	}
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:

@@ -518,9 +537,25 @@ static int inv_mpu6050_write_raw(struct iio_dev *indio_dev,
 				 struct iio_chan_spec const *chan,
 				 int val, int val2, long mask)
 {
-	struct inv_mpu6050_state  *st = iio_priv(indio_dev);
+	struct inv_mpu6050_state *st = iio_priv(indio_dev);
+	int chan_index;
 	int result;
 
+	if (chan > indio_dev->channels + indio_dev->num_channels ||
+			chan < indio_dev->channels)
+		return -EINVAL;
+	chan_index = chan - indio_dev->channels;
+	if (chan_index >= INV_MPU6050_NUM_INT_CHAN) {
+		struct inv_mpu_ext_chan_state *ext_chan_state =
+				&st->ext_chan[chan_index - INV_MPU6050_NUM_INT_CHAN];
+		struct inv_mpu_ext_sens_state *ext_sens_state =
+				&st->ext_sens[ext_chan_state->ext_sens_index];
+		struct iio_dev *orig_dev = ext_sens_state->orig_dev;
+		const struct iio_chan_spec *orig_chan =
+				&orig_dev->channels[ext_chan_state->orig_chan_index];
+		return orig_dev->info->write_raw(orig_dev, orig_chan, val, val2, mask);
+	}
+
 	mutex_lock(&indio_dev->mlock);
 	/*
 	 * we should only update scale when the chip is disabled, i.e.

@@ -809,6 +844,346 @@ static const struct iio_info mpu_info = {
 	.validate_trigger = inv_mpu6050_validate_trigger,
 };
 
+extern struct device_type iio_device_type;
+
+static int iio_device_from_i2c_client_match(struct device *dev, void *data)
+{
+	return dev->type == &iio_device_type;
+}
+
+static struct iio_dev* iio_device_from_i2c_client(struct i2c_client* i2c)
+{
+	struct device *child;
+
+	child = device_find_child(&i2c->dev, NULL, iio_device_from_i2c_client_match);
+
+	return (child ? dev_to_iio_dev(child) : NULL);
+}
+
+static int inv_mpu_slave_enable(struct inv_mpu6050_state *st, int index, bool state)
+{
+	return regmap_update_bits(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(index),
+				  INV_MPU6050_BIT_I2C_SLV_EN,
+				  state ? INV_MPU6050_BIT_I2C_SLV_EN : 0);
+}
+
+/* Enable slaves based on scan mask */
+int inv_mpu_slave_enable_mask(struct inv_mpu6050_state *st,
+			      const unsigned long mask)
+{
+	int i, result;
+
+	for (i = 0; i < INV_MPU6050_MAX_EXT_SENSORS; ++i) {
+		long slave_mask = st->ext_sens[i].scan_mask;
+		result = inv_mpu_slave_enable(st, i, slave_mask & mask);
+		if (result)
+			return result;
+	}
+
+	return 0;
+}
+
+static int inv_mpu_parse_one_ext_sens(struct device *dev,
+				      struct device_node *np,
+				      struct inv_mpu_ext_sens_spec *spec)
+{
+	int result;
+	u32 addr, reg, len;
+
+	result = of_property_read_u32(np, "invensense,addr", &addr);
+	if (result)
+		return result;
+	result = of_property_read_u32(np, "invensense,reg", &reg);
+	if (result)
+		return result;
+	result = of_property_read_u32(np, "invensense,len", &len);
+	if (result)
+		return result;
+
+	spec->addr = addr;
+	spec->reg = reg;
+	spec->len = len;
+
+	result = of_property_count_u32_elems(np, "invensense,external-channels");
+	if (result < 0)
+		return result;
+	spec->num_ext_channels = result;
+	spec->ext_channels = devm_kmalloc(dev, spec->num_ext_channels * sizeof(*spec->ext_channels), GFP_KERNEL);
+	if (!spec->ext_channels)
+		return -ENOMEM;
+	result = of_property_read_u32_array(np, "invensense,external-channels",
+					    spec->ext_channels,
+					    spec->num_ext_channels);
+	if (result)
+		return result;
+
+	return 0;
+}
+
+static int inv_mpu_parse_ext_sens(struct device *dev,
+				  struct device_node *node,
+				  struct inv_mpu_ext_sens_spec *specs)
+{
+	struct device_node *child;
+	int result;
+	u32 reg;
+
+	for_each_available_child_of_node(node, child) {
+		result = of_property_read_u32(child, "reg", &reg);
+		if (result)
+			return result;
+		if (reg > INV_MPU6050_MAX_EXT_SENSORS) {
+			dev_err(dev, "External sensor index %u out of range, max %d\n",
+				reg, INV_MPU6050_MAX_EXT_SENSORS);
+			return -EINVAL;
+		}
+		result = inv_mpu_parse_one_ext_sens(dev, child, &specs[reg]);
+		if (result)
+			return result;
+	}
+
+	return 0;
+}
+
+static int inv_mpu_get_ext_sens_spec(struct iio_dev *indio_dev)
+{
+	struct inv_mpu6050_state *st = iio_priv(indio_dev);
+	struct device *dev = regmap_get_device(st->map);
+	struct device_node *node;
+	int result;
+
+	node = of_get_child_by_name(dev->of_node, "invensense,external-sensors");
+	if (node) {
+		result = inv_mpu_parse_ext_sens(dev, node, st->ext_sens_spec);
+		if (result)
+			dev_err(dev, "Failed to parsing external-sensors devicetree data\n");
+		return result;
+	}
+
+	return 0;
+}
+
+/* Struct used while enumerating devices and matching them */
+struct inv_mpu_handle_ext_sensor_fnarg
+{
+	struct iio_dev *indio_dev;
+
+	/* Current scan index */
+	int scan_index;
+	/* Current channel index */
+	int chan_index;
+	/* Non-const pointer to channels */
+	struct iio_chan_spec *channels;
+};
+
+/*
+ * Write initial configuration of a slave at probe time.
+ *
+ * This is mostly fixed except for enabling/disabling individual slaves.
+ */
+static int inv_mpu_config_external_read(struct inv_mpu6050_state *st, int index,
+					const struct inv_mpu_ext_sens_spec *spec)
+{
+	int result;
+
+	result = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_ADDR(index),
+			      INV_MPU6050_BIT_I2C_SLV_RW | spec->addr);
+	if (result)
+		return result;
+	result = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_REG(index), spec->reg);
+	if (result)
+		return result;
+	result = regmap_write(st->map, INV_MPU6050_REG_I2C_SLV_CTRL(index),
+			      spec->len);
+	if (result)
+		return result;
+
+	return result;
+}
+
+/* Handle one device */
+static int inv_mpu_handle_slave_device(
+		struct inv_mpu_handle_ext_sensor_fnarg *fnarg,
+		int slave_index,
+		struct iio_dev *orig_dev)
+{
+	int i, j;
+	int data_offset;
+	struct iio_dev *indio_dev = fnarg->indio_dev;
+	struct inv_mpu6050_state *st = iio_priv(indio_dev);
+	struct device *mydev = regmap_get_device(st->map);
+	struct inv_mpu_ext_sens_spec *ext_sens_spec =
+			&st->ext_sens_spec[slave_index];
+	struct inv_mpu_ext_sens_state *ext_sens_state =
+			&st->ext_sens[slave_index];
+
+	dev_info(mydev, "slave %d is device %s\n",
+			slave_index, orig_dev->name ?: dev_name(&orig_dev->dev));
+	ext_sens_state->orig_dev = orig_dev;
+	ext_sens_state->scan_mask = 0;
+	data_offset = 0;
+
+	/* handle channels: */
+	for (i = 0; i < ext_sens_spec->num_ext_channels; ++i) {
+		int orig_chan_index = -1;
+		const struct iio_chan_spec *orig_chan_spec;
+		struct iio_chan_spec *chan_spec;
+		struct inv_mpu_ext_chan_state *chan_state;
+
+		for (j = 0; j < orig_dev->num_channels; ++j)
+			if (orig_dev->channels[j].scan_index == ext_sens_spec->ext_channels[i]) {
+				orig_chan_index = j;
+				break;
+			}
+
+		if (orig_chan_index < 0) {
+			dev_err(mydev, "Could not find slave channel with scan_index %d\n",
+					ext_sens_spec->ext_channels[i]);
+		}
+
+		orig_chan_spec = &orig_dev->channels[orig_chan_index];
+		chan_spec = &fnarg->channels[INV_MPU6050_NUM_INT_CHAN + fnarg->chan_index];
+		chan_state = &st->ext_chan[fnarg->chan_index];
+
+		chan_state->ext_sens_index = slave_index;
+		chan_state->orig_chan_index = orig_chan_index;
+		chan_state->data_offset = data_offset;
+		memcpy(chan_spec, orig_chan_spec, sizeof(struct iio_chan_spec));
+		chan_spec->scan_index = fnarg->scan_index;
+		ext_sens_state->scan_mask |= (1 << chan_spec->scan_index);
+
+		fnarg->scan_index++;
+		fnarg->chan_index++;
+		data_offset += chan_spec->scan_type.storagebits / 8;
+		dev_info(mydev, "Reading external channel #%d scan_index %d data_offset %d"
+				" from original device %s chan #%d scan_index %d\n",
+				fnarg->chan_index, chan_spec->scan_index, chan_state->data_offset,
+				orig_dev->name ?: dev_name(&orig_dev->dev), orig_chan_index, orig_chan_spec->scan_index);
+	}
+	if (ext_sens_spec->len != data_offset) {
+		dev_err(mydev, "slave %d length mismatch between "
+				"i2c slave read length (%d) and "
+				"sum of channel sizes (%d)\n",
+				slave_index, ext_sens_spec->len, data_offset);
+		return -EINVAL;
+	}
+
+	return inv_mpu_config_external_read(st, slave_index, ext_sens_spec);
+}
+
+/* device_for_each_child enum function */
+static int inv_mpu_handle_ext_sensor_fn(struct device *dev, void *data)
+{
+	struct inv_mpu_handle_ext_sensor_fnarg *fnarg = data;
+	struct iio_dev *indio_dev = fnarg->indio_dev;
+	struct inv_mpu6050_state *st = iio_priv(indio_dev);
+	struct i2c_client *client;
+	struct iio_dev *orig_dev;
+	int i, result;
+
+	client = i2c_verify_client(dev);
+	if (!client)
+		return 0;
+	orig_dev = iio_device_from_i2c_client(client);
+	if (!orig_dev)
+		return 0;
+
+	for (i = 0; i < INV_MPU6050_MAX_EXT_SENSORS; ++i) {
+		if (st->ext_sens_spec[i].addr != client->addr)
+			continue;
+		if (st->ext_sens[i].orig_dev) {
+			dev_warn(&indio_dev->dev, "already found slave with at addr %d\n", client->addr);
+			continue;
+		}
+
+		result = inv_mpu_handle_slave_device(fnarg, i, orig_dev);
+		if (result)
+			return result;
+	}
+	return 0;
+}
+
+static int inv_mpu6050_handle_ext_sensors(struct iio_dev *indio_dev)
+{
+	struct inv_mpu6050_state *st = iio_priv(indio_dev);
+	struct device *dev = regmap_get_device(st->map);
+	struct inv_mpu_handle_ext_sensor_fnarg fnarg = {
+		.indio_dev = indio_dev,
+		.chan_index = 0,
+		.scan_index = INV_MPU6050_SCAN_TIMESTAMP,
+	};
+	int i, result;
+	int num_ext_chan = 0, sum_data_len = 0;
+	int num_scan_elements;
+
+	inv_mpu_get_ext_sens_spec(indio_dev);
+	for (i = 0; i < INV_MPU6050_MAX_EXT_SENSORS; ++i) {
+		num_ext_chan += st->ext_sens_spec[i].num_ext_channels;
+		sum_data_len += st->ext_sens_spec[i].len;
+	}
+	if (sum_data_len > INV_MPU6050_CNT_EXT_SENS_DATA) {
+		dev_err(dev, "Too many bytes from external sensors:"
+			      " requested=%d max=%d\n",
+			      sum_data_len, INV_MPU6050_CNT_EXT_SENS_DATA);
+		return -EINVAL;
+	}
+
+	/* Allocate scan_offsets/scan_lengths */
+	num_scan_elements = INV_MPU6050_NUM_INT_SCAN_ELEMENTS + num_ext_chan;
+	st->scan_offsets = devm_kmalloc(dev, num_scan_elements * sizeof(int), GFP_KERNEL);
+	if (!st->scan_offsets)
+		return -ENOMEM;
+	st->scan_lengths = devm_kmalloc(dev, num_scan_elements * sizeof(int), GFP_KERNEL);
+	if (!st->scan_lengths)
+		return -ENOMEM;
+
+	/* Zero length means nothing to do, just publish internal channels */
+	if (!sum_data_len) {
+		indio_dev->channels = inv_mpu_channels;
+		indio_dev->num_channels = INV_MPU6050_NUM_INT_CHAN;
+		BUILD_BUG_ON(ARRAY_SIZE(inv_mpu_channels) != INV_MPU6050_NUM_INT_CHAN);
+		return 0;
+	}
+
+	indio_dev->num_channels = INV_MPU6050_NUM_INT_CHAN + num_ext_chan;
+	indio_dev->channels = fnarg.channels = devm_kmalloc(dev,
+			indio_dev->num_channels * sizeof(struct iio_chan_spec),
+			GFP_KERNEL);
+	if (!fnarg.channels)
+		return -ENOMEM;
+	memcpy(fnarg.channels, inv_mpu_channels, sizeof(inv_mpu_channels));
+	memset(fnarg.channels + INV_MPU6050_NUM_INT_CHAN, 0,
+	       num_ext_chan * sizeof(struct iio_chan_spec));
+
+	st->ext_chan = devm_kzalloc(dev, num_ext_chan * sizeof(*st->ext_chan), GFP_KERNEL);
+	if (!st->ext_chan)
+		return -ENOMEM;
+
+	result = inv_mpu6050_set_power_itg(st, true);
+	if (result < 0)
+		return result;
+
+	result = device_for_each_child(&st->aux_master_adapter.dev, &fnarg,
+				       inv_mpu_handle_ext_sensor_fn);
+	if (result)
+		goto out_disable;
+	/* Timestamp channel has index 0 and last scan_index */
+	fnarg.channels[0].scan_index = fnarg.scan_index;
+
+	if (fnarg.chan_index != num_ext_chan) {
+		dev_err(&indio_dev->dev, "Failed to match all external channels!\n");
+		result = -EINVAL;
+		goto out_disable;
+	}
+
+	result = inv_mpu6050_set_power_itg(st, false);
+	return result;
+
+out_disable:
+	inv_mpu6050_set_power_itg(st, false);
+	return result;
+}
+
 /**
  *  inv_check_and_setup_chip() - check and setup chip.
  */

@@ -1140,8 +1515,6 @@ int inv_mpu_core_probe(struct regmap *regmap, int irq, const char *name,
 		indio_dev->name = name;
 	else
 		indio_dev->name = dev_name(dev);
-	indio_dev->channels = inv_mpu_channels;
-	indio_dev->num_channels = ARRAY_SIZE(inv_mpu_channels);
 
 	indio_dev->info = &mpu_info;
 	indio_dev->modes = INDIO_BUFFER_TRIGGERED;

@@ -1179,6 +1552,12 @@ int inv_mpu_core_probe(struct regmap *regmap, int irq, const char *name,
 	}
 #endif
 
+	result = inv_mpu6050_handle_ext_sensors(indio_dev);
+	if (result < 0) {
+		dev_err(dev, "failed to configure channels %d\n", result);
+		goto out_remove_trigger;
+	}
+
 	INIT_KFIFO(st->timestamps);
 	spin_lock_init(&st->time_stamp_lock);
 	result = iio_device_register(indio_dev);

drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h +69 -5

index ec1401d..56fd943 100644
@@ -110,6 +110,45 @@ struct inv_mpu6050_hw {
 	const struct inv_mpu6050_chip_config *config;
 };
 
+/* Maximum external sensors */
+/* These are SLV0-3 in HW, SLV4 is reserved for i2c master */
+#define INV_MPU6050_MAX_EXT_SENSORS 4
+
+/* Number of internal channels */
+#define INV_MPU6050_NUM_INT_CHAN 8
+
+/* Number of internal scan elements (channels with scan_index >= 0) */
+#define INV_MPU6050_NUM_INT_SCAN_ELEMENTS 7
+
+/* Specification for an external sensor */
+struct inv_mpu_ext_sens_spec {
+	unsigned short addr;
+	u8 reg, len;
+
+	int num_ext_channels;
+	int *ext_channels;
+};
+
+/* Driver state for each external sensor */
+struct inv_mpu_ext_sens_state {
+	struct iio_dev *orig_dev;
+
+	/* Mask of all channels in this sensor */
+	unsigned long scan_mask;
+};
+
+/* Driver state for each external channel */
+struct inv_mpu_ext_chan_state {
+	/* Index inside state->ext_sens */
+	int ext_sens_index;
+
+	/* Index inside orig_dev->channels */
+	int orig_chan_index;
+
+	/* Relative to first offset for this slave */
+	int data_offset;
+};
+
 /*
  *  struct inv_mpu6050_state - Driver state variables.
  *  @TIMESTAMP_FIFO_SIZE: fifo size for timestamp.

@@ -153,10 +192,13 @@ struct inv_mpu6050_state {
 	u8 slv4_done_status;
 #endif
 
-#define INV_MPU6050_MAX_SCAN_ELEMENTS 7
-	unsigned int scan_offsets[INV_MPU6050_MAX_SCAN_ELEMENTS];
-	unsigned int scan_lengths[INV_MPU6050_MAX_SCAN_ELEMENTS];
+	unsigned int *scan_offsets;
+	unsigned int *scan_lengths;
 	bool realign_required;
+
+	struct inv_mpu_ext_sens_spec ext_sens_spec[INV_MPU6050_MAX_EXT_SENSORS];
+	struct inv_mpu_ext_sens_state ext_sens[INV_MPU6050_MAX_EXT_SENSORS];
+	struct inv_mpu_ext_chan_state *ext_chan;
 };
 
 /*register and associated bit definition*/

@@ -171,6 +213,24 @@ struct inv_mpu6050_state {
 #define INV_MPU6050_REG_FIFO_EN             0x23
 #define INV_MPU6050_BIT_ACCEL_OUT           0x08
 #define INV_MPU6050_BITS_GYRO_OUT           0x70
+#define INV_MPU6050_BIT_SLV0_FIFO_EN        0x01
+#define INV_MPU6050_BIT_SLV1_FIFO_EN        0x02
+#define INV_MPU6050_BIT_SLV2_FIFO_EN        0x04
+#define INV_MPU6050_BIT_SLV2_FIFO_EN        0x04
+
+/* SLV3 fifo enabling is not in REG_FIFO_EN */
+#define INV_MPU6050_REG_MST_CTRL	    0x24
+#define INV_MPU6050_BIT_SLV3_FIFO_EN        0x20
+
+/* For slaves 0-3 */
+#define INV_MPU6050_REG_I2C_SLV_ADDR(i)     (0x25 + 3 * (i))
+#define INV_MPU6050_REG_I2C_SLV_REG(i)      (0x26 + 3 * (i))
+#define INV_MPU6050_REG_I2C_SLV_CTRL(i)     (0x27 + 3 * (i))
+#define INV_MPU6050_BIT_I2C_SLV_RW          0x80
+#define INV_MPU6050_BIT_I2C_SLV_EN          0x80
+#define INV_MPU6050_BIT_I2C_SLV_BYTE_SW     0x40
+#define INV_MPU6050_BIT_I2C_SLV_REG_DIS     0x20
+#define INV_MPU6050_BIT_I2C_SLV_REG_GRP     0x10
 
 #define INV_MPU6050_REG_I2C_SLV4_ADDR       0x31
 #define INV_MPU6050_BIT_I2C_SLV4_R          0x80

@@ -247,8 +307,8 @@ struct inv_mpu6050_state {
 #define INV_MPU6050_GYRO_CONFIG_FSR_SHIFT    3
 #define INV_MPU6050_ACCL_CONFIG_FSR_SHIFT    3
 
-/* 6 + 6 round up and plus 8 */
-#define INV_MPU6050_OUTPUT_DATA_SIZE         24
+/* max is 3*2 accel + 3*2 gyro + 24 external + 8 ts */
+#define INV_MPU6050_OUTPUT_DATA_SIZE         44
 
 #define INV_MPU6050_REG_INT_PIN_CFG	0x37
 #define INV_MPU6050_BIT_BYPASS_EN	0x2

@@ -261,6 +321,9 @@ struct inv_mpu6050_state {
 #define INV_MPU6050_MIN_FIFO_RATE            4
 #define INV_MPU6050_ONE_K_HZ                 1000
 
+#define INV_MPU6050_REG_EXT_SENS_DATA_00	0x49
+#define INV_MPU6050_CNT_EXT_SENS_DATA		24
+
 #define INV_MPU6050_REG_WHOAMI			117
 
 #define INV_MPU6000_WHOAMI_VALUE		0x68

@@ -328,6 +391,7 @@ int inv_mpu6050_probe_trigger(struct iio_dev *indio_dev);
 void inv_mpu6050_remove_trigger(struct inv_mpu6050_state *st);
 int inv_reset_fifo(struct iio_dev *indio_dev);
 int inv_mpu6050_switch_engine(struct inv_mpu6050_state *st, bool en, u32 mask);
+int inv_mpu_slave_enable_mask(struct inv_mpu6050_state *st, const unsigned long mask);
 int inv_mpu6050_write_reg(struct inv_mpu6050_state *st, int reg, u8 val);
 int inv_mpu6050_set_power_itg(struct inv_mpu6050_state *st, bool power_on);
 int inv_mpu_acpi_create_mux_client(struct i2c_client *client);

drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +52 -13

index 49e503c..919148a 100644
@@ -30,7 +30,9 @@ static void inv_mpu_get_scan_offsets(
 		const unsigned int masklen,
 		unsigned int *scan_offsets)
 {
+	struct inv_mpu6050_state *st = iio_priv(indio_dev);
 	unsigned int pos = 0;
+	int i, j;
 
 	if (*mask & INV_MPU6050_SCAN_MASK_ACCEL) {
 		scan_offsets[INV_MPU6050_SCAN_ACCL_X] = pos + 0;

@@ -44,6 +46,24 @@ static void inv_mpu_get_scan_offsets(
 		scan_offsets[INV_MPU6050_SCAN_GYRO_Z] = pos + 4;
 		pos += 6;
 	}
+	/* HW lays out channels in slave order */
+	for (i = 0; i < INV_MPU6050_MAX_EXT_SENSORS; ++i) {
+		struct inv_mpu_ext_sens_spec *ext_sens_spec;
+		struct inv_mpu_ext_sens_state *ext_sens_state;
+		ext_sens_spec = &st->ext_sens_spec[i];
+		ext_sens_state = &st->ext_sens[i];
+
+		if (!(ext_sens_state->scan_mask & *mask))
+			continue;
+		for (j = 0; j + INV_MPU6050_NUM_INT_CHAN < indio_dev->num_channels; ++j) {
+			const struct iio_chan_spec *chan;
+			if (st->ext_chan[j].ext_sens_index != i)
+				continue;
+			chan = &indio_dev->channels[j + INV_MPU6050_NUM_INT_CHAN];
+			scan_offsets[chan->scan_index] = pos + st->ext_chan[j].data_offset;
+		}
+		pos += ext_sens_spec->len;
+	}
 }
 
 /* This is slowish but relatively common */

@@ -138,6 +158,10 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 	result = regmap_write(st->map, st->reg->fifo_en, 0);
 	if (result)
 		goto reset_fifo_fail;
+	result = regmap_update_bits(st->map, INV_MPU6050_REG_MST_CTRL,
+				    INV_MPU6050_BIT_SLV3_FIFO_EN, 0);
+	if (result)
+		goto reset_fifo_fail;
 	/* disable fifo reading */
 	st->chip_config.user_ctrl &= ~INV_MPU6050_BIT_FIFO_EN;
 	result = regmap_write(st->map, st->reg->user_ctrl,

@@ -155,14 +179,12 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 	inv_clear_kfifo(st);
 
 	/* enable interrupt */
-	if (st->chip_config.accl_fifo_enable ||
-	    st->chip_config.gyro_fifo_enable) {
-		result = regmap_update_bits(st->map, st->reg->int_enable,
-					    INV_MPU6050_BIT_DATA_RDY_EN,
-					    INV_MPU6050_BIT_DATA_RDY_EN);
-		if (result)
-			return result;
-	}
+	result = regmap_update_bits(st->map, st->reg->int_enable,
+				    INV_MPU6050_BIT_DATA_RDY_EN,
+				    INV_MPU6050_BIT_DATA_RDY_EN);
+	if (result)
+		return result;
+
 	/* enable FIFO reading and I2C master interface*/
 	st->chip_config.user_ctrl |= INV_MPU6050_BIT_FIFO_EN;
 	result = regmap_write(st->map, st->reg->user_ctrl,

@@ -175,9 +197,22 @@ int inv_reset_fifo(struct iio_dev *indio_dev)
 		d |= INV_MPU6050_BITS_GYRO_OUT;
 	if (st->chip_config.accl_fifo_enable)
 		d |= INV_MPU6050_BIT_ACCEL_OUT;
+	if (*indio_dev->active_scan_mask & st->ext_sens[0].scan_mask)
+		d |= INV_MPU6050_BIT_SLV0_FIFO_EN;
+	if (*indio_dev->active_scan_mask & st->ext_sens[1].scan_mask)
+		d |= INV_MPU6050_BIT_SLV1_FIFO_EN;
+	if (*indio_dev->active_scan_mask & st->ext_sens[2].scan_mask)
+		d |= INV_MPU6050_BIT_SLV2_FIFO_EN;
 	result = regmap_write(st->map, st->reg->fifo_en, d);
 	if (result)
 		goto reset_fifo_fail;
+	if (*indio_dev->active_scan_mask & st->ext_sens[3].scan_mask) {
+		result = regmap_update_bits(st->map, INV_MPU6050_REG_MST_CTRL,
+					    INV_MPU6050_BIT_SLV3_FIFO_EN,
+					    INV_MPU6050_BIT_SLV3_FIFO_EN);
+		if (result)
+			goto reset_fifo_fail;
+	}
 
 	/* check realign required */
 	inv_mpu_get_scan_offsets(indio_dev, mask, masklen, st->scan_offsets);

@@ -222,8 +257,9 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct inv_mpu6050_state *st = iio_priv(indio_dev);
-	size_t bytes_per_datum;
+	size_t bytes_per_datum = 0;
 	int result;
+	int i;
 	u8 data[INV_MPU6050_OUTPUT_DATA_SIZE];
 	u16 fifo_count;
 	s64 timestamp;

@@ -236,15 +272,18 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 	spi = i2c ? NULL: to_spi_device(regmap_dev);
 
 	mutex_lock(&indio_dev->mlock);
-	if (!(st->chip_config.accl_fifo_enable |
-		st->chip_config.gyro_fifo_enable))
-		goto end_session;
+
+	/* Sample length */
 	bytes_per_datum = 0;
 	if (st->chip_config.accl_fifo_enable)
 		bytes_per_datum += INV_MPU6050_BYTES_PER_3AXIS_SENSOR;
-
 	if (st->chip_config.gyro_fifo_enable)
 		bytes_per_datum += INV_MPU6050_BYTES_PER_3AXIS_SENSOR;
+	for (i = 0; i < INV_MPU6050_MAX_EXT_SENSORS; ++i)
+		if (st->ext_sens[i].scan_mask & *indio_dev->active_scan_mask)
+			bytes_per_datum += st->ext_sens_spec[i].len;
+	if (!bytes_per_datum)
+		return 0;
 
 	/*
 	 * read fifo_count register to know how many bytes inside FIFO

drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c +9 -0

index a334ed9..39e791b 100644
@@ -61,6 +61,11 @@ static int inv_mpu6050_set_enable(struct iio_dev *indio_dev, bool enable)
 			if (result)
 				return result;
 		}
+
+		result = inv_mpu_slave_enable_mask(st, *indio_dev->active_scan_mask);
+		if (result)
+			return result;
+
 		result = inv_reset_fifo(indio_dev);
 		if (result)
 			return result;

@@ -80,6 +85,10 @@ static int inv_mpu6050_set_enable(struct iio_dev *indio_dev, bool enable)
 		if (result)
 			return result;
 
+		result = inv_mpu_slave_enable_mask(st, 0);
+		if (result)
+			return result;
+
 		result = inv_mpu6050_switch_engine(st, false,
 					INV_MPU6050_BIT_PWR_GYRO_STBY);
 		if (result)