Re: [PATCH v2 1/3] iio: accel: bmc150: use aligned scan buffer for both trigger and fifo

On Sat, 15 Aug 2026 23:27:26 +0530
Yash Suthar <[email protected]> wrote:

> Drop buffer as duplicate and s16 is not correct we needed __le16 as little
> endian, keep scan at the end of the bmc150_accel_data struct with
> IIO_DMA_MINALIGN, and use it for both paths.
> 
> Fixes: bd7fe5b71918 ("iio: accel: BMC150 accel support")
> Suggested-by: Jonathan Cameron <[email protected]>
> Signed-off-by: Yash Suthar <[email protected]>
> ---
>  drivers/iio/accel/bmc150-accel-core.c |  4 ++--
>  drivers/iio/accel/bmc150-accel.h      | 14 +++++---------
>  2 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> index dc8a6285cf3d..89a475ef9a9b 100644
> --- a/drivers/iio/accel/bmc150-accel-core.c
> +++ b/drivers/iio/accel/bmc150-accel-core.c
> @@ -1191,12 +1191,12 @@ static irqreturn_t bmc150_accel_trigger_handler(int irq, void *p)
>  
>  	mutex_lock(&data->mutex);

Relevant to the next patch - what is this lock actually protecting?
At first glance I'd assume the buffer, but then we drop the lock before
we are done with that.


>  	ret = regmap_bulk_read(data->regmap, BMC150_ACCEL_REG_XOUT_L,
> -			       data->buffer, AXIS_MAX * 2);
> +			       data->scan.channels, AXIS_MAX * 2);
>  	mutex_unlock(&data->mutex);
>  	if (ret < 0)
>  		goto err_read;
>  
> -	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
> +	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,

This is still using scan, but the lock has been released.

>  					   pf->timestamp);
>  err_read:
>  	iio_trigger_notify_done(indio_dev->trig);
> diff --git a/drivers/iio/accel/bmc150-accel.h b/drivers/iio/accel/bmc150-accel.h
> index e8f26198359f..9deff256aed5 100644
> --- a/drivers/iio/accel/bmc150-accel.h
> +++ b/drivers/iio/accel/bmc150-accel.h
> @@ -64,15 +64,6 @@ struct bmc150_accel_data {
>  	struct bmc150_accel_trigger triggers[BMC150_ACCEL_TRIGGERS];
>  	struct mutex mutex;
>  	u8 fifo_mode, watermark;
> -	s16 buffer[8];
> -	/*
> -	 * Ensure there is sufficient space and correct alignment for
> -	 * the timestamp if enabled
> -	 */
> -	struct {
> -		__le16 channels[3];
> -		aligned_s64 ts;
> -	} scan;
>  	u8 bw_bits;
>  	u32 slope_dur;
>  	u32 slope_thres;
> @@ -85,6 +76,11 @@ struct bmc150_accel_data {
>  	void (*resume_callback)(struct device *dev);
>  	struct delayed_work resume_work;
>  	struct iio_mount_matrix orientation;
> +	/* Ensure correct alignment of timestamp and DMA safety */
> +	struct {
> +		__le16 channels[3];
> +		aligned_s64 ts;
> +	} scan __aligned(IIO_DMA_MINALIGN);
>  };
>  
>  int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,