On Tue, Sep 25, 2018 at 10:36:54PM +0800, Phil Reid wrote:
> On 25/09/2018 9:30 PM, Jonathan Cameron wrote:
> > > +static irqreturn_t rm3100_trigger_handler(int irq, void *p)
> > > +{
> > > + struct iio_poll_func *pf = p;
> > > + struct iio_dev *indio_dev = pf->indio_dev;
> > > + struct rm3100_data *data = iio_priv(indio_dev);
> > > + struct regmap *regmap = data->regmap;
> > > + u8 buffer[9];
> > > + int ret;
> > > + int i;
> > > +
> > > + mutex_lock(&data->lock);
> > > + ret = rm3100_wait_measurement(data);
> > > + if (ret < 0) {
> > > + mutex_unlock(&data->lock);
> > > + goto done;
> > > + }
> > > +
> > > + ret = regmap_bulk_read(regmap, RM3100_REG_MX2, buffer, sizeof(buffer));
> > > + mutex_unlock(&data->lock);
> > > + if (ret < 0)
> > > + goto done;
> > > +
> > > + /* Convert XXXYYYZZZxxx to XXXxYYYxZZZx. x for padding. */
> > > + for (i = 0; i < 3; i++)
> > > + memcpy(data->buffer + i * 4, buffer + i * 3, 3);
> > Firstly X doesn't need copying.
> > Secondly the copy of Y actually overwrites the value of Z
> > XXXYYYZZZxxx
> > XXXxYYYZZxxx
> > XXXxYYYxYZZx
> >
> > I think...
> >
> > > +
> > > + iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
> > > + iio_get_time_ns(indio_dev));
>
> memcpy target is a different buffer so should be ok.
>
> But that raises the question of does it need to be?
> 'buffer' could be 12 bytes long and just shuffle Z then Y.
> Do the unused bytes need to be zeroed? or does libiio mask them anyway?
>
>
>
> --
> Regards
> Phil Reid
Hi Phil,
This is interesting, last patch I submitted uses three transactions and
shuffles X, Y and Z respectively. You said it should be better to use one
transactions, I thought it makes point, and one transaction may reduce
IO pressure of the i2c bus. :)
And that's not necessary for unused bytes to be zero. I'm not familiar
with libiio, actually just been studying it, can't say anything about
it.
yours,
Song Qiang
