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);
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