On 08/01/2015 05:58 AM, Matt Ranostay wrote: [...] > + > +struct lidar_data { > + struct mutex lock; > + struct iio_dev *indio_dev; > + struct i2c_client *client; > + > + /* config */ > + int calib_bias; > + > + u16 buffer[5]; /* 2 byte distance + 8 byte timestamp */ Needs to be in its own cacheline to avoid issues if the I2C controller is using DMA. u16 buffer[5] ____cacheline_aligned; > +}; [...] > +static inline int lidar_read_byte(struct lidar_data *data, int reg) I'd drop the inline. The compiler is smart enough to figure out whether it makes sense to inline it or not. > +{ > + struct i2c_client *client = data->client; > + int ret; > + > + ret = i2c_smbus_write_byte(client, reg); > + if (ret < 0) { > + dev_err(&client->dev, "cannot write addr value"); > + return ret; > + } > + > + ret = i2c_smbus_read_byte(client); > + if (ret < 0) { > + dev_err(&client->dev, "cannot read data value"); > + return ret; > + } Instead of using a write_byte/read_byte combination rather use i2c_smbus_read_byte_data(). I think that will do the same, but in one atomic operation. > + > + return ret; > +} [...] > +static int lidar_read_measurement(struct lidar_data *data, u16 *reg) > +{ > + int ret; > + int val; > + > + ret = lidar_read_byte(data, LIDAR_REG_DATA_HBYTE); > + if (ret < 0) > + return ret; > + val = ret << 8; > + > + ret = lidar_read_byte(data, LIDAR_REG_DATA_LBYTE); > + if (ret < 0) > + return ret; > + val |= ret; > + > + /* correct any possible overflow or underflow */ > + val += data->calib_bias / 10000; Typically calib bias is only meant for a offset correction that is done in hardware rather than in software. What's the usecase for doing it in kernelspace rather than in userspace? > + if (val < 0) > + val = 0; > + > + if (val > LIDAR_REG_DATA_MAX) > + val = LIDAR_REG_DATA_MAX; > + > + *reg = val; > + > + return 0; > +} [...] > +static int lidar_read_raw(struct iio_dev *indio_dev, > + struct iio_chan_spec const *chan, > + int *val, int *val2, long mask) > +{ > + struct lidar_data *data = iio_priv(indio_dev); > + int ret = -EINVAL; > + > + if (iio_buffer_enabled(indio_dev) && mask == IIO_CHAN_INFO_RAW) > + return -EBUSY; > + > + mutex_lock(&data->lock); > + > + switch (mask) { > + case IIO_CHAN_INFO_RAW: { > + u16 reg; > + > + ret = lidar_get_measurement(data, ®); > + if (!ret) { > + *val = reg / 100; > + *val2 = (reg % 100) * 10000; > + ret = IIO_VAL_INT_PLUS_MICRO; The raw attribute is supposed to return the raw value as a IIO_VAL_INT. A scale attribute should be used to indicate the conversion factor to get the proper unit. > + } > + break; > + } > + case IIO_CHAN_INFO_CALIBBIAS: > + *val = 0; > + *val2 = data->calib_bias; > + ret = IIO_VAL_INT_PLUS_MICRO; > + break; > + } > + > + mutex_unlock(&data->lock); > + > + return ret; > +} [...] > +static struct iio_info lidar_info = { const > + .driver_module = THIS_MODULE, > + .read_raw = lidar_read_raw, > + .write_raw = lidar_write_raw, > +}; [...] > +static struct i2c_driver lidar_driver = { > + .driver = { > + .name = LIDAR_DRV_NAME, > + .owner = THIS_MODULE, You added a DT vendor prefix, but there is no of match table for the driver. > + }, > + .probe = lidar_probe, > + .remove = lidar_remove, > + .id_table = lidar_id, > +}; > +module_i2c_driver(lidar_driver); -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html