linux-kernel - Re: [PATCH] iio: proximity: hx9023s: use IIO_DECLARE_BUFFER_WITH

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Message-ID: <57e16589-3d9c-49c1-ba91-abae23143803@baylibre.com>
Date: Wed, 23 Jul 2025 10:07:55 -0500
From: David Lechner <dlechner@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: proximity: hx9023s: use IIO_DECLARE_BUFFER_WITH_TS()

On 7/22/25 5:54 PM, David Lechner wrote:
> Use stack-allocated IIO_DECLARE_BUFFER_WITH_TS() to declare the buffer
> that gets used with iio_push_to_buffers_with_ts().
> 
> We change from a struct to IIO_DECLARE_BUFFER_WITH_TS() since
> HX9023S_CH_NUM is 5 making channels[] larger than 8 bytes and therefore
> the timestamp is not always as the same position depending on the number
> of channels enabled in the scan.
> 
> And since the data structure is not used outside of the scope of the
> interrupt handler, the array does not need to be in the driver state
> struct and can just be stack-allocated.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
>  drivers/iio/proximity/hx9023s.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/proximity/hx9023s.c b/drivers/iio/proximity/hx9023s.c
> index 33781c3147286fb3e2f022201ccf7e908d0b6b12..1203fa4bc7512ea85b55d537e2459104b52407b9 100644
> --- a/drivers/iio/proximity/hx9023s.c
> +++ b/drivers/iio/proximity/hx9023s.c
> @@ -143,12 +143,6 @@ struct hx9023s_data {
>  	unsigned long chan_in_use;
>  	unsigned int prox_state_reg;
>  	bool trigger_enabled;
> -
> -	struct {
> -		__le16 channels[HX9023S_CH_NUM];
> -		aligned_s64 ts;
> -	} buffer;
> -
>  	/*
>  	 * Serialize access to registers below:
>  	 * HX9023S_PROX_INT_LOW_CFG,
> @@ -928,6 +922,7 @@ static const struct iio_trigger_ops hx9023s_trigger_ops = {
>  
>  static irqreturn_t hx9023s_trigger_handler(int irq, void *private)
>  {
> +	IIO_DECLARE_BUFFER_WITH_TS(__le16, channels, HX9023S_CH_NUM);

Ooof. I remembered to zero-initialize all of the scan structs in the other
similar patches, but forgot we need to do the same with the array to avoid
leaking uninitialized stack to usespace.

	IIO_DECLARE_BUFFER_WITH_TS(__le16, channels, HX9023S_CH_NUM) = { };

>  	struct iio_poll_func *pf = private;
>  	struct iio_dev *indio_dev = pf->indio_dev;
>  	struct hx9023s_data *data = iio_priv(indio_dev);
> @@ -950,11 +945,11 @@ static irqreturn_t hx9023s_trigger_handler(int irq, void *private)
>  
>  	iio_for_each_active_channel(indio_dev, bit) {
>  		index = indio_dev->channels[bit].channel;
> -		data->buffer.channels[i++] = cpu_to_le16(data->ch_data[index].diff);
> +		channels[i++] = cpu_to_le16(data->ch_data[index].diff);
>  	}
>  
> -	iio_push_to_buffers_with_ts(indio_dev, &data->buffer,
> -				    sizeof(data->buffer), pf->timestamp);
> +	iio_push_to_buffers_with_ts(indio_dev, channels, sizeof(channels),
> +				    pf->timestamp);
>  
>  out:
>  	iio_trigger_notify_done(indio_dev->trig);
>