[PATCH v2] iio: st_sensors: add debugfs register read hook

[Linus Walleij <linus.walleij@linaro.org>]

This adds a debugfs hook to read/write registers in the ST
sensors using debugfs. Proved to be awesome help when trying
to debug why IRQs do not arrive.

Cc: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v1->v2:
- User &ampersand i front of function name for debugfs helper
- EXPORT the debugfs regread symbol so modules work
---
 drivers/iio/accel/st_accel_core.c               |  1 +
 drivers/iio/common/st_sensors/st_sensors_core.c | 22 ++++++++++++++++++++++
 drivers/iio/gyro/st_gyro_core.c                 |  1 +
 drivers/iio/magnetometer/st_magn_core.c         |  1 +
 drivers/iio/pressure/st_pressure_core.c         |  1 +
 include/linux/iio/common/st_sensors.h           |  4 ++++
 6 files changed, 30 insertions(+)

diff --git a/drivers/iio/accel/st_accel_core.c b/drivers/iio/accel/st_accel_core.c
index 6617e779aa87..058c87d9f564 100644
--- a/drivers/iio/accel/st_accel_core.c
+++ b/drivers/iio/accel/st_accel_core.c
@@ -612,6 +612,7 @@ static const struct iio_info accel_info = {
 	.attrs = &st_accel_attribute_group,
 	.read_raw = &st_accel_read_raw,
 	.write_raw = &st_accel_write_raw,
+	.debugfs_reg_access = &st_sensors_debugfs_reg_access,
 };
 
 #ifdef CONFIG_IIO_TRIGGER
diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
index 8086cbcff87d..3129128857ea 100644
--- a/drivers/iio/common/st_sensors/st_sensors_core.c
+++ b/drivers/iio/common/st_sensors/st_sensors_core.c
@@ -44,6 +44,28 @@ st_sensors_write_data_with_mask_error:
 	return err;
 }
 
+int st_sensors_debugfs_reg_access(struct iio_dev *indio_dev,
+				  unsigned reg, unsigned writeval,
+				  unsigned *readval)
+{
+	struct st_sensor_data *sdata = iio_priv(indio_dev);
+	u8 readdata;
+	int err;
+
+	if (!readval)
+		return sdata->tf->write_byte(&sdata->tb, sdata->dev,
+					     (u8)reg, (u8)writeval);
+
+	err = sdata->tf->read_byte(&sdata->tb, sdata->dev, (u8)reg, &readdata);
+	if (err < 0)
+		return err;
+
+	*readval = (unsigned)readdata;
+
+	return 0;
+}
+EXPORT_SYMBOL(st_sensors_debugfs_reg_access);
+
 static int st_sensors_match_odr(struct st_sensor_settings *sensor_settings,
 			unsigned int odr, struct st_sensor_odr_avl *odr_out)
 {
diff --git a/drivers/iio/gyro/st_gyro_core.c b/drivers/iio/gyro/st_gyro_core.c
index ffe96642b6d0..3bbe63117175 100644
--- a/drivers/iio/gyro/st_gyro_core.c
+++ b/drivers/iio/gyro/st_gyro_core.c
@@ -380,6 +380,7 @@ static const struct iio_info gyro_info = {
 	.attrs = &st_gyro_attribute_group,
 	.read_raw = &st_gyro_read_raw,
 	.write_raw = &st_gyro_write_raw,
+	.debugfs_reg_access = &st_sensors_debugfs_reg_access,
 };
 
 #ifdef CONFIG_IIO_TRIGGER
diff --git a/drivers/iio/magnetometer/st_magn_core.c b/drivers/iio/magnetometer/st_magn_core.c
index b4bcfb790f49..d612069e4e70 100644
--- a/drivers/iio/magnetometer/st_magn_core.c
+++ b/drivers/iio/magnetometer/st_magn_core.c
@@ -475,6 +475,7 @@ static const struct iio_info magn_info = {
 	.attrs = &st_magn_attribute_group,
 	.read_raw = &st_magn_read_raw,
 	.write_raw = &st_magn_write_raw,
+	.debugfs_reg_access = &st_sensors_debugfs_reg_access,
 };
 
 int st_magn_common_probe(struct iio_dev *indio_dev)
diff --git a/drivers/iio/pressure/st_pressure_core.c b/drivers/iio/pressure/st_pressure_core.c
index e881fa6291e9..84f965deff80 100644
--- a/drivers/iio/pressure/st_pressure_core.c
+++ b/drivers/iio/pressure/st_pressure_core.c
@@ -397,6 +397,7 @@ static const struct iio_info press_info = {
 	.attrs = &st_press_attribute_group,
 	.read_raw = &st_press_read_raw,
 	.write_raw = &st_press_write_raw,
+	.debugfs_reg_access = &st_sensors_debugfs_reg_access,
 };
 
 #ifdef CONFIG_IIO_TRIGGER
diff --git a/include/linux/iio/common/st_sensors.h b/include/linux/iio/common/st_sensors.h
index 2c476acb87d9..d8b4a7bc4029 100644
--- a/include/linux/iio/common/st_sensors.h
+++ b/include/linux/iio/common/st_sensors.h
@@ -269,6 +269,10 @@ void st_sensors_power_enable(struct iio_dev *indio_dev);
 
 void st_sensors_power_disable(struct iio_dev *indio_dev);
 
+int st_sensors_debugfs_reg_access(struct iio_dev *indio_dev,
+				  unsigned reg, unsigned writeval,
+				  unsigned *readval);
+
 int st_sensors_set_odr(struct iio_dev *indio_dev, unsigned int odr);
 
 int st_sensors_set_dataready_irq(struct iio_dev *indio_dev, bool enable);
-- 
2.4.3