linux-kernel - Re: [PATCH v2] iio: accel: bma180: use stack allocated buffer for scan

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Message-ID: <wwwdesuaxl4w32cf6l2bna4bixrxe4pwy4i3briysda3mjvnku@wyvpeirvf34y>
Date: Tue, 22 Jul 2025 10:12:04 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 
	Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: accel: bma180: use stack allocated buffer for
 scan

On Mon, Jul 21, 2025 at 06:16:34PM -0500, David Lechner wrote:
> Move the scan struct to the stack instead of being in the driver state
> struct. The buffer is only used in a single function and does not need
> to be DMA-safe so it does not need to exist outside of that function's
> scope.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
> Changes in v2:
> - Preserve the struct instead of using IIO_DECLARE_BUFFER_WITH_TS()
> - Did not pick up Andy's review tag since the entire patch changed.
> - Link to v1: https://lore.kernel.org/r/20250710-iio-use-more-iio_declare_buffer_with_ts-v1-1-df6498f54095@baylibre.com
> ---

Reviewed-by: Nuno Sá <nuno.sa@...log.com>

>  drivers/iio/accel/bma180.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/accel/bma180.c b/drivers/iio/accel/bma180.c
> index 4fccbcb76e0423bee37463a72c637af80e356a19..8925f5279e627a67c8e2928b10bee04185663e10 100644
> --- a/drivers/iio/accel/bma180.c
> +++ b/drivers/iio/accel/bma180.c
> @@ -139,11 +139,6 @@ struct bma180_data {
>  	int scale;
>  	int bw;
>  	bool pmode;
> -	/* Ensure timestamp is naturally aligned */
> -	struct {
> -		s16 chan[4];
> -		aligned_s64 timestamp;
> -	} scan;
>  };
>  
>  enum bma180_chan {
> @@ -870,6 +865,10 @@ static irqreturn_t bma180_trigger_handler(int irq, void *p)
>  	struct bma180_data *data = iio_priv(indio_dev);
>  	s64 time_ns = iio_get_time_ns(indio_dev);
>  	int bit, ret, i = 0;
> +	struct {
> +		s16 chan[4];
> +		aligned_s64 timestamp;
> +	} scan = { };
>  
>  	mutex_lock(&data->mutex);
>  
> @@ -879,12 +878,12 @@ static irqreturn_t bma180_trigger_handler(int irq, void *p)
>  			mutex_unlock(&data->mutex);
>  			goto err;
>  		}
> -		data->scan.chan[i++] = ret;
> +		scan.chan[i++] = ret;
>  	}
>  
>  	mutex_unlock(&data->mutex);
>  
> -	iio_push_to_buffers_with_ts(indio_dev, &data->scan, sizeof(data->scan), time_ns);
> +	iio_push_to_buffers_with_ts(indio_dev, &scan, sizeof(scan), time_ns);
>  err:
>  	iio_trigger_notify_done(indio_dev->trig);
>  
> 
> ---
> base-commit: cd2731444ee4e35db76f4fb587f12d327eec5446
> change-id: 20250710-iio-use-more-iio_declare_buffer_with_ts-0924382d38c6
> 
> Best regards,
> -- 
> David Lechner <dlechner@...libre.com>
>