RE: [PATCH 4/4] iio:pressure: preenable/postenable/predisable fixup for ST press buffer

[Denis CIOCCA <denis.ciocca@st.com>]

Hi Alexandru,

> -----Original Message-----
> From: Ardelean, Alexandru <alexandru.Ardelean@analog.com>
> Sent: Tuesday, July 30, 2019 2:02 AM
> To: jic23@kernel.org; Denis CIOCCA <denis.ciocca@st.com>; linux-
> iio@vger.kernel.org
> Subject: Re: [PATCH 4/4] iio:pressure: preenable/postenable/predisable
> fixup for ST press buffer
> 
> On Mon, 2019-07-29 at 17:03 -0700, Denis Ciocca wrote:
> > [External]
> >
> > This patch is trying to cleanup for good the buffers operation functions.
> > There is no need of using preenable, all can be done into postenable.
> > Let's also use logical sequence of operations as already done in accel
> > driver.
> > Finally also rename the goto label using operation to perform and not
> > where it fails.
> >
> 
> Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> 
> 
> Unrelated to this patch, I was thinking that it would be a neat idea to move
> the `buffer_data` allocation in
> `drivers/iio/common/st_sensors/st_sensors_buffer.c`
> 
> This would remove some duplication of this alloc + free in drivers.
> 
> Maybe in st_sensors_trigger_handler() something like:
> 
> if (!sdata->buffer_data) {
>     sdata->buffer_data = devm_kmalloc()
>     if (!sdata->buffer_data) {
>         dev_err(indio_dev->dev, "Failed to allocate buffer data\n");
>         goto st_sensors_get_buffer_element_error;
>     }
> }
> 
> Using devm_kmalloc() or a similar devm_ variant would be neat, since it gets
> free'd when the device gets removed.

Not sure about the solution proposed.
Memory allocation is actually related to how many channels are enabled,
one possibility could be to allocate the maximum but not sure it's worth...
Moreover the memory allocation there could let driver miss the first sample I guess.


> 
> Thanks
> Alex
> 
> > Signed-off-by: Denis Ciocca <denis.ciocca@st.com>
> > ---
> >  drivers/iio/pressure/st_pressure_buffer.c | 32
> > ++++++++---------------
> >  1 file changed, 11 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/iio/pressure/st_pressure_buffer.c
> > b/drivers/iio/pressure/st_pressure_buffer.c
> > index f21b630abaa0..54823cfcfab5 100644
> > --- a/drivers/iio/pressure/st_pressure_buffer.c
> > +++ b/drivers/iio/pressure/st_pressure_buffer.c
> > @@ -29,53 +29,43 @@ int st_press_trig_set_state(struct iio_trigger *trig,
> bool state)
> >  	return st_sensors_set_dataready_irq(indio_dev, state);  }
> >
> > -static int st_press_buffer_preenable(struct iio_dev *indio_dev) -{
> > -	return st_sensors_set_enable(indio_dev, true);
> > -}
> > -
> >  static int st_press_buffer_postenable(struct iio_dev *indio_dev)  {
> > -	int err;
> >  	struct st_sensor_data *press_data = iio_priv(indio_dev);
> > +	int err;
> >
> >  	press_data->buffer_data = kmalloc(indio_dev->scan_bytes,
> >  					  GFP_DMA | GFP_KERNEL);
> > -	if (press_data->buffer_data == NULL) {
> > -		err = -ENOMEM;
> > -		goto allocate_memory_error;
> > -	}
> > +	if (!press_data->buffer_data)
> > +		return -ENOMEM;
> >
> >  	err = iio_triggered_buffer_postenable(indio_dev);
> >  	if (err < 0)
> > -		goto st_press_buffer_postenable_error;
> > +		goto st_press_free_buffer;
> >
> > -	return err;
> > +	return st_sensors_set_enable(indio_dev, true);
> >
> > -st_press_buffer_postenable_error:
> > +st_press_free_buffer:
> >  	kfree(press_data->buffer_data);
> > -allocate_memory_error:
> >  	return err;
> >  }
> >
> >  static int st_press_buffer_predisable(struct iio_dev *indio_dev)
> >  {
> > -	int err;
> >  	struct st_sensor_data *press_data = iio_priv(indio_dev);
> > -
> > -	err = iio_triggered_buffer_predisable(indio_dev);
> > -	if (err < 0)
> > -		goto st_press_buffer_predisable_error;
> > +	int err, err2;
> >
> >  	err = st_sensors_set_enable(indio_dev, false);
> >
> > -st_press_buffer_predisable_error:
> > +	err2 = iio_triggered_buffer_predisable(indio_dev);
> > +	if (!err)
> > +		err = err2;
> > +
> >  	kfree(press_data->buffer_data);
> >  	return err;
> >  }
> >
> >  static const struct iio_buffer_setup_ops st_press_buffer_setup_ops = {
> > -	.preenable = &st_press_buffer_preenable,
> >  	.postenable = &st_press_buffer_postenable,
> >  	.predisable = &st_press_buffer_predisable,
> >  };