Hello,
> > +static int ltr501_read_raw(struct iio_dev *indio_dev,
> > + struct iio_chan_spec const *chan,
> > + int *val, int *val2, long mask)
> > +{
> > + struct ltr501_data *data = iio_priv(indio_dev);
> > + __le16 buf[2];
> > + int ret, i;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_RAW:
> > + if (iio_buffer_enabled(indio_dev))
> > + return -EBUSY;
> > +
> > + switch (chan->type) {
> > + case IIO_INTENSITY:
> > + ret = ltr501_drdy(data, LTR501_STATUS_ALS_RDY);
> > + if (ret < 0)
> > + return ret;
> > + /* always read both ALS channels in given order */
> > + ret = i2c_smbus_read_i2c_block_data(data->client,
> > + LTR501_ALS_DATA1, sizeof(buf), (u8 *) buf);
> > + if (ret < 0)
> > + return ret;
> > + *val = le16_to_cpu(chan->address == LTR501_ALS_DATA1 ?
> > + buf[0] : buf[1]);
> > + return IIO_VAL_INT;
> > + case IIO_PROXIMITY:
> > + ret = ltr501_drdy(data, LTR501_STATUS_PS_RDY);
> > + if (ret < 0)
> > + return ret;
> > + ret = i2c_smbus_read_word_data(data->client,
> > + chan->address);
> > + if (ret < 0)
> > + return ret;
> > + *val = ret & LTR501_PS_DATA_MASK;
> > + return IIO_VAL_INT;
>
> Will anything bad happen if two processes concurrently read from the device?
ALS and PS measurements use separate registers and therefore should not
interfere
at first I'd have said the worst thing would be that the same data is read
twice... however, the data ready loop can be an issue:
two processes wait for data to become available: one process sees the
drdy bit and by reading the data resets the drdy, the other process
does not see the drdy and decrements its retry counter and may eventually
report a failed IO
so, I'll add two separate mutexse for ALS and PS
regards, p.
--
Peter Meerwald
+43-664-2444418 (mobile)
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