Hi Shubhrajyoti,
On 02/15/2011 12:47 PM, Shubhrajyoti wrote:
> Hi Michael,
>
>> +static IIO_DEV_ATTR_IN_RAW(6, ad7298_scan, 6);
>> +static IIO_DEV_ATTR_IN_RAW(7, ad7298_scan, 7);
>> +
>> +static ssize_t ad7298_show_temp(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + /* Driver currently only support internal vref */
>> + struct iio_dev *dev_info = dev_get_drvdata(dev);
>> + struct ad7298_state *st = iio_dev_get_devdata(dev_info);
>> + unsigned short tmp;
>> + char sign;
>> +
>> + tmp = cpu_to_be16(AD7298_WRITE | AD7298_TSENSE |
>> + AD7298_TAVG | st->ext_ref);
>>
> didnt understand why you needed the cpu_to_be16 here?
>
The AD7298, like almost any SPI slave device, uses MSB first.
tmp is type unsigned short. SPI uses 8-bit transfers by default.
The pointer to tmp is handed to spi_write. So on a little endian machine
it would transfer the low byte instead of high byte first.
cpu_to_be16() flips the byte order on LE and does nothing on BE.
>> +
>> + spi_write(st->spi, (u8 *)&tmp, 2);
>> + tmp = 0;
>> + spi_write(st->spi, (u8 *)&tmp, 2);
>> + usleep_range(101, 1000); /* sleep> 100us */
>> + spi_read(st->spi, (u8 *)&tmp, 2);
>> +
>> + tmp = be16_to_cpu(tmp)& RES_MASK(AD7298_BITS);
>> +
>> + /*
>> + * One LSB of the ADC corresponds to 0.25 deg C.
>> + * The temperature reading is in 12-bit twos complement format
>> + */
>> +
>> + if (tmp& (1<< (AD7298_BITS - 1))) {
>> + tmp = (1<< AD7298_BITS) - tmp;
>> + sign = '-';
>> + } else {
>> + sign = '+';
>> + }
>> +
>> + return sprintf(buf, "%c%d.%.2d\n", sign, tmp / 4, (tmp& 3) * 25);
>> +}
>> +
>> +static IIO_DEVICE_ATTR(temp, S_IRUGO, ad7298_show_temp, NULL, 0);
>>
>>
> <snip>
>
>> +
>> +static int ad7298_remove(struct spi_device *spi)
>>
> May consider __devexit
>
Good catch.
>> +{
>> + struct ad7298_state *st = spi_get_drvdata(spi);
>> + struct iio_dev *indio_dev = st->indio_dev;
>> +
>> + iio_ring_buffer_unregister(indio_dev->ring);
>> + ad7298_ring_cleanup(indio_dev);
>> + iio_device_unregister(indio_dev);
>> + if (!IS_ERR(st->reg)) {
>> + regulator_disable(st->reg);
>> + regulator_put(st->reg);
>> + }
>> + kfree(st);
>> + return 0;
>> +}
>> +
>> +static const struct spi_device_id ad7298_id[] = {
>> + {"ad7298", 0},
>> + {}
>> +};
>> +
>> +static struct spi_driver ad7298_driver = {
>> + .driver = {
>> + .name = "ad7298",
>> + .bus =&spi_bus_type,
>> + .owner = THIS_MODULE,
>> + },
>> + .probe = ad7298_probe,
>> + .remove = __devexit_p(ad7298_remove),
>> + .id_table = ad7298_id,
>> +};
>> +
>> +static int __init ad7298_init(void)
>> +{
>> + return spi_register_driver(&ad7298_driver);
>> +}
>> +module_init(ad7298_init);
>> +
>> +static void __exit ad7298_exit(void)
>> +{
>> + spi_unregister_driver(&ad7298_driver);
>> +}
>>
> <snip>
>
>> + ret = -ENOMEM;
>> + goto error_ret;
>> + }
>> + ret = ring->access.read_last(ring, (u8 *) ring_data);
>> + if (ret)
>> + goto error_free_ring_data;
>> +
>> + ret = be16_to_cpu(ring_data[ch]);
>> +
>> +error_free_ring_data:
>> + kfree(ring_data);
>> +error_ret:
>> + return ret;
>> +}
>> +
>> +/**
>> + * ad7298_ring_preenable() setup the parameters of the ring before enabling
>> + *
>> + * The complex nature of the setting of the nuber of bytes per datum is due
>>
> typo number.
>
Thanks
>> + * to this driver currently ensuring that the timestamp is stored at an 8
>> + * byte boundary.
>> + **/
>> +static int ad7298_ring_preenable(struct iio_dev *indio_dev)
>> +{
>> + struct ad7298_state *st = indio_dev->dev_data;
>> + struct iio_ring_buffer *ring = indio_dev->ring;
>> + size_t d_size;
>> + int i, m;
>> + unsigned short command;
>> +
>> + d_size = ring->scan_count *
>> + (AD7298_STORAGE_BITS / 8) + sizeof(s64);
>> +
>> + if (d_size % sizeof(s64))
>> + d_size += sizeof(s64) - (d_size % sizeof(s64));
>> +
>> + if (ring->access.set_bytes_per_datum)
>> + ring->access.set_bytes_per_datum(ring, d_size);
>> +
>> + st->d_size = d_size;
>> +
>> + command = AD7298_WRITE | st->ext_ref;
>> +
>> + for (i = 0, m = AD7298_CH0; i< AD7298_MAX_CHAN; i++, m>>= 1)
>> + if (ring->scan_mask& (1<< i))
>> + command |= m;
>> +
>> + st->tx_buf[0] = cpu_to_be16(command);
>> +
>> + /* build spi ring message */
>> + st->ring_xfer[0].tx_buf =&st->tx_buf[0];
>> + st->ring_xfer[0].len = 2;
>> + st->ring_xfer[0].cs_change = 1;
>> + st->ring_xfer[1].tx_buf =&st->tx_buf[1];
>> + st->ring_xfer[1].len = 2;
>> + st->ring_xfer[1].cs_change = 1;
>> +
>> + spi_message_init(&st->ring_msg);
>> + spi_message_add_tail(&st->ring_xfer[0],&st->ring_msg);
>> + spi_message_add_tail(&st->ring_xfer[1],&st->ring_msg);
>> +
>> + for (i = 0; i< ring->scan_count; i++) {
>> + st->ring_xfer[i + 2].rx_buf =&st->rx_buf[i];
>> + st->ring_xfer[i + 2].len = 2;
>> + st->ring_xfer[i + 2].cs_change = 1;
>> + spi_message_add_tail(&st->ring_xfer[i + 2],&st->ring_msg);
>> + }
>> + /* make sure last transfer cs_change is not set */
>> + st->ring_xfer[i + 1].cs_change = 0;
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * ad7298_poll_func_th() th of trigger launched polling to ring buffer
>> + *
>> + * As sampling only occurs on spi comms occuring, leave timestamping until
>> + * then. Some triggers will generate their own time stamp. Currently
>> + * there is no way of notifying them when no one cares.
>> + **/
>> +static void ad7298_poll_func_th(struct iio_dev *indio_dev, s64 time)
>> +{
>> + struct ad7298_state *st = indio_dev->dev_data;
>> +
>> + schedule_work(&st->poll_work);
>> + return;
>> +}
>> +/**
>> + * ad7298_poll_bh_to_ring() bh of trigger launched polling to ring buffer
>> + * @work_s: the work struct through which this was scheduled
>> + *
>> + * Currently there is no option in this driver to disable the saving of
>> + * timestamps within the ring.
>> + * I think the one copy of this at a time was to avoid problems if the
>> + * trigger was set far too high and the reads then locked up the computer.
>> + **/
>> +static void ad7298_poll_bh_to_ring(struct work_struct *work_s)
>> +{
>> + struct ad7298_state *st = container_of(work_s, struct ad7298_state,
>> + poll_work);
>> + struct iio_dev *indio_dev = st->indio_dev;
>> + struct iio_sw_ring_buffer *sw_ring = iio_to_sw_ring(indio_dev->ring);
>> + struct iio_ring_buffer *ring = indio_dev->ring;
>> + s64 time_ns;
>> + __u16 buf[16];
>>
> Any reason for using __u16
>
No
>> + int b_sent, i;
>> +
>> + /* Ensure only one copy of this function running at a time */
>> + if (atomic_inc_return(&st->protect_ring)> 1)
>> + return;
>> +
>> + b_sent = spi_sync(st->spi,&st->ring_msg);
>>
>
--
Greetings,
Michael
--
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