Re: [PATCH 01/16] iio: introduced iio_push_to_buffers_with_ts() that takes a total_len argument.

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 10 Mar 2025 08:34:50 +0000
Nuno Sá <noname.nuno@gmail.com> wrote:

> On Sun, 2025-03-09 at 18:20 +0000, Jonathan Cameron wrote:
> > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > 
> > Check that total_len argument against iio_dev->scan_bytes.
> > 
> > The size needs to be at least as big as the scan. It can be larger,
> > which is typical if only part of fixed sized storage is used due to
> > a subset of channels being enabled.
> > 
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > ---
> >  include/linux/iio/buffer.h | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h
> > index 3b8d618bb3df..75d5e58b646b 100644
> > --- a/include/linux/iio/buffer.h
> > +++ b/include/linux/iio/buffer.h
> > @@ -45,6 +45,19 @@ static inline int iio_push_to_buffers_with_timestamp(struct
> > iio_dev *indio_dev,
> >  	return iio_push_to_buffers(indio_dev, data);
> >  }
> >  
> > +static inline int iio_push_to_buffers_with_ts(struct iio_dev *indio_dev,
> > +					      void *data, size_t total_len,
> > +					      int64_t timestamp)
> > +{  
> 
> Kind of a nitpick but what about data_len as the size relate to *data?
Maybe data_total_len? I kind of want to make people wonder what the total
is about and read the docs. Which I forgot to actually add :(
This has always been a quirky, non obvious interface.

> 
> > +	if (total_len < indio_dev->scan_bytes) {  
> 
> Given this is to be called on a fastpath and that the above is clearly a bug,
> what do you think about unlikely(total_len < indio_dev->scan_bytes) for some
> micro optimization?

Fair point.  Probably never matters as any branch predictor ought to get this
one quickly but it also acts as documentation so sure.

> 
> Anyways, this looks like a nice API improvement to me!
> 
> - Nuno Sá 
> >