Re: [PATCH] iio:st_magn: enable trigger before enabling sensor

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 25 Oct 2018 15:32:26 -0700
Denis Ciocca <denis.ciocca@st.com> wrote:

> From logical point of view driver should be ready to
> receive irqs before enabling the sensor itself.
> This patch is fixing also an issue related to
> sensors that generate interrupts unconditionally,
> (DRDY pads) when interrupt level is used.
> 
> Signed-off-by: Martin Kelly <martin@martingkelly.com>
> Signed-off-by: Denis Ciocca <denis.ciocca@st.com>
A couple of very minor points inline.

Also, author should match the first sign off.  I kind of lost touch of
how much got modified, but a Reported-by: or the one you occasionally get
is Originated-by: for martin would be preferred if the changes are major,
if they are minor, then the author should be martin with a sign off
from Denis.

Also, as I understand it this is a fix for an issue seen, so make that
clear in the naming of the patch and give a fixes-tag to indicate
how far back we should apply this in stable.

Thanks,

Jonathan

> ---
>  drivers/iio/magnetometer/st_magn_buffer.c | 33 +++++++++++------------
>  1 file changed, 16 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iio/magnetometer/st_magn_buffer.c b/drivers/iio/magnetometer/st_magn_buffer.c
> index 0a9e8fadfa9d..097e6e88a464 100644
> --- a/drivers/iio/magnetometer/st_magn_buffer.c
> +++ b/drivers/iio/magnetometer/st_magn_buffer.c
> @@ -30,11 +30,6 @@ int st_magn_trig_set_state(struct iio_trigger *trig, bool state)
>  	return st_sensors_set_dataready_irq(indio_dev, state);
>  }
>  
> -static int st_magn_buffer_preenable(struct iio_dev *indio_dev)
> -{
> -	return st_sensors_set_enable(indio_dev, true);
> -}
> -
>  static int st_magn_buffer_postenable(struct iio_dev *indio_dev)
>  {
>  	int err;
> @@ -42,40 +37,44 @@ static int st_magn_buffer_postenable(struct iio_dev *indio_dev)
>  
>  	mdata->buffer_data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
>  	if (mdata->buffer_data == NULL) {
> -		err = -ENOMEM;
> -		goto allocate_memory_error;
> +		return -ENOMEM;
I would have a very slight preference for that having been in a separate patch.
Good cleanup but not part of the main point of this patch.

>  	}
>  
>  	err = iio_triggered_buffer_postenable(indio_dev);
>  	if (err < 0)
> -		goto st_magn_buffer_postenable_error;
> +		goto st_magn_buffer_free_buffer_data;
> +
> +	err = st_sensors_set_enable(indio_dev, true);
> +	if (err < 0)
> +		goto st_magn_buffer_buffer_predisable;
>  
>  	return err;
>  
> -st_magn_buffer_postenable_error:
> +st_magn_buffer_buffer_predisable:
> +	iio_triggered_buffer_predisable(indio_dev);
> +st_magn_buffer_free_buffer_data:
>  	kfree(mdata->buffer_data);
> -allocate_memory_error:
>  	return err;
>  }
>  
>  static int st_magn_buffer_predisable(struct iio_dev *indio_dev)
>  {
> -	int err;
> +	int err = 0, err2;
>  	struct st_sensor_data *mdata = iio_priv(indio_dev);
>  
> -	err = iio_triggered_buffer_predisable(indio_dev);
> -	if (err < 0)
> -		goto st_magn_buffer_predisable_error;
> +	err2 = st_sensors_set_enable(indio_dev, false);
> +	if (err2 < 0)
> +		err = err2;
>  
> -	err = st_sensors_set_enable(indio_dev, false);
> +	err2 = iio_triggered_buffer_predisable(indio_dev);
> +	if (err2 < 0)
> +		err = err2;
There is a small argument that we should have some visibility of
the value of the error from st_sensors_set_enable if both
error paths trigger.  I think the suggestion made in the
other review of an error comment would solve that fairly well.

>  
> -st_magn_buffer_predisable_error:
>  	kfree(mdata->buffer_data);
>  	return err;
>  }
>  
>  static const struct iio_buffer_setup_ops st_magn_buffer_setup_ops = {
> -	.preenable = &st_magn_buffer_preenable,
>  	.postenable = &st_magn_buffer_postenable,
>  	.predisable = &st_magn_buffer_predisable,
>  };