Re: [PATCH v2 03/11] iio: add watermark logic to iio read and poll

[Octavian Purdila <octavian.purdila@intel.com>]

On Sun, Jan 25, 2015 at 11:22 PM, Hartmut Knaack <knaack.h@gmx.de> wrote:
>
> Octavian Purdila schrieb am 21.12.2014 um 01:42:
> > From: Josselin Costanzi <josselin.costanzi@mobile-devices.fr>
> >
> > Currently the IIO buffer blocking read only wait until at least one
> > data element is available.
> > This patch makes the reader sleep until enough data is collected before
> > returning to userspace. This should limit the read() calls count when
> > trying to get data in batches.
> >
>
> Hi,
> I have a question and a minor recommendation, please see inline.
>

Thanks for looking at this.

Any feedback on the hardware buffer stuff? We are still trying to find
the right ABIs. I did not get feedback after my last reply, did it got
lost?

<snip>

> >       struct iio_dev *indio_dev = filp->private_data;
> >       struct iio_buffer *rb = indio_dev->buffer;
> > +     size_t datum_size = rb->bytes_per_datum;
> > +     size_t to_read = min_t(size_t, n / datum_size, rb->low_watermark);
> Are you sure that rb->bytes_per_datum can not be zero, when accessed here? From
> what I could see, there is a chance of it being zero, if the scan_mask is clear
> and timestamps are disabled.
>

Good catch, I will fix that.

> > +
> > +     /* We can't just test for watermark to decide if we wake the poll queue
> > +      * because read may request less samples than the watermark
> I think this comment could end with a full stop. Also, first line should be
> empty.
>

Correct.