On 18/11/15 01:49, Matt Ranostay wrote:
> Remove racey i2c_smbus_read_byte() calls in measurement
> reading function with an single i2c_transfer.
>
> Signed-off-by: Matt Ranostay <mranostay@xxxxxxxxx>
As with the lidar sensor, this requires a more sophisticated I2C master
so you should be checking if it is capable of doing what you need here.
Also, ideally provide a fallback to smbus for those cases where the
controller isn't sophisticated enough with appropriate locking to protect
the device...
Jonathan
> ---
> drivers/iio/chemical/vz89x.c | 33 +++++++++++++++++++++++----------
> 1 file changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iio/chemical/vz89x.c b/drivers/iio/chemical/vz89x.c
> index 11e59a5..c03f988 100644
> --- a/drivers/iio/chemical/vz89x.c
> +++ b/drivers/iio/chemical/vz89x.c
> @@ -100,27 +100,40 @@ static int vz89x_measurement_is_valid(struct vz89x_data *data)
> return !!(data->buffer[VZ89X_REG_MEASUREMENT_SIZE - 1] > 0);
> }
>
> +static int vz89x_i2c_xfer(struct vz89x_data *data, u8 cmd)
> +{
> + struct i2c_client *client = data->client;
> + struct i2c_msg msg[2];
> + int ret;
> + u8 buf[3] = { cmd, 0, 0};
> +
> + msg[0].addr = client->addr;
> + msg[0].flags = client->flags;
> + msg[0].len = 3;
> + msg[0].buf = (char *) &buf;
> +
> + msg[1].addr = client->addr;
> + msg[1].flags = client->flags | I2C_M_RD;
> + msg[1].len = VZ89X_REG_MEASUREMENT_SIZE;
> + msg[1].buf = (char *) &data->buffer;
> +
> + ret = i2c_transfer(client->adapter, msg, 2);
> +
> + return (ret == VZ89X_REG_MEASUREMENT_SIZE) ? 0 : ret;
> +}
> +
> static int vz89x_get_measurement(struct vz89x_data *data)
> {
> int ret;
> - int i;
>
> /* sensor can only be polled once a second max per datasheet */
> if (!time_after(jiffies, data->last_update + HZ))
> return 0;
>
> - ret = i2c_smbus_write_word_data(data->client,
> - VZ89X_REG_MEASUREMENT, 0);
> + ret = vz89x_i2c_xfer(data, VZ89X_REG_MEASUREMENT);
> if (ret < 0)
> return ret;
>
> - for (i = 0; i < VZ89X_REG_MEASUREMENT_SIZE; i++) {
> - ret = i2c_smbus_read_byte(data->client);
> - if (ret < 0)
> - return ret;
> - data->buffer[i] = ret;
> - }
> -
> ret = vz89x_measurement_is_valid(data);
> if (ret)
> return -EAGAIN;
>
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