[PATCH v2 0/3] iio: accel: bmc150: DMA-safe buffers and use iio_push_to_buffers_with_ts()

[PATCH v2 0/3] iio: accel: bmc150: DMA-safe buffers and use iio_push_to_buffers_with_ts()

[Yash Suthar]

The trigger path used a plain s16 buffer while the FIFO path already had
a properly typed scan member (__le16 + aligned timestamp). Those two
buffers did the same job, and s16 does not represent little-endian data.
Drop the duplicate, keep scan at the end of struct bmc150_accel_data with
IIO_DMA_MINALIGN, and use it for both the trigger and FIFO paths.

The FIFO and read_raw buffers are passed to regmap bulk/raw reads, which
is not DMA-safe. Move them into struct bmc150_accel_data after scan and
aligned to IIO_DMA_MINALIGN.

Finally, replace the deprecated iio_push_to_buffers_with_timestamp() with
iio_push_to_buffers_with_ts() so the push sites pass an explicit buffer
size.

This supersedes the earlier standalone patches:
Link: https://lore.kernel.org/linux-iio/20260808220236.421832-1-yashsuthar983@gmail.com/
Link: https://lore.kernel.org/linux-iio/20260809111303.496393-1-yashsuthar983@gmail.com/

Link to v1: https://lore.kernel.org/all/20260814101845.301769-1-yashsuthar983@gmail.com/

Changes in v2:
- patch 1: restore early error check flow
- patch 2: keep fifo_buff declaration in one line

Yash Suthar (3):
  iio: accel: bmc150: use aligned scan buffer for both trigger and fifo
  iio: accel: bmc150: use DMA-safe buffers for regmap bulk reads
  iio: accel: bmc150: use iio_push_to_buffers_with_ts()

 drivers/iio/accel/bmc150-accel-core.c | 24 +++++++++++-------------
 drivers/iio/accel/bmc150-accel.h      | 19 ++++++++++---------
 2 files changed, 21 insertions(+), 22 deletions(-)

-- 
2.43.0

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

[Yash Suthar]

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 <jic23@kernel.org>
Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>
---
 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);
 	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,
 					   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,
-- 
2.43.0

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

[Linus Walleij]

On Sat, Aug 15, 2026 at 7:57 PM Yash Suthar <yashsuthar983@gmail.com> 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 <jic23@kernel.org>
> Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>

Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij

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

[Jonathan Cameron]

On Sat, 15 Aug 2026 23:27:26 +0530
Yash Suthar <yashsuthar983@gmail.com> 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 <jic23@kernel.org>
> Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>
> ---
>  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);
>  	ret = regmap_bulk_read(data->regmap, BMC150_ACCEL_REG_XOUT_L,
> -			       data->buffer, AXIS_MAX * 2);
> +			       data->scan.channels, AXIS_MAX * 2);

Even nicer if you replace AXIS_MAX * 2 with sizeof(data->scan.channels)
and also drop the AXIS_MAX definition as no longer used.


>  	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,
>  					   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,

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

[Jonathan Cameron]

On Sat, 15 Aug 2026 23:27:26 +0530
Yash Suthar <yashsuthar983@gmail.com> 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 <jic23@kernel.org>
> Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>
> ---
>  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,

[PATCH v2 2/3] iio: accel: bmc150: use DMA-safe buffers for regmap bulk reads

[Yash Suthar]

The FIFO and read_raw buffers are passed to regmap bulk/raw reads
,which is not DMA-safe.Moved them into struct bmc150_accel_data
after scan, each aligned to IIO_DMA_MINALIGN.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>
---
 drivers/iio/accel/bmc150-accel-core.c | 14 ++++++--------
 drivers/iio/accel/bmc150-accel.h      |  5 +++++
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
index 89a475ef9a9b..e8d27fd1be3f 100644
--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -125,7 +125,6 @@
 #define BMC150_ACCEL_REG_FIFO_CONFIG0		0x30
 #define BMC150_ACCEL_REG_FIFO_CONFIG1		0x3E
 #define BMC150_ACCEL_REG_FIFO_DATA		0x3F
-#define BMC150_ACCEL_FIFO_LENGTH		32
 
 enum bmc150_accel_axis {
 	AXIS_X,
@@ -622,7 +621,6 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
 	struct device *dev = regmap_get_device(data->regmap);
 	int ret;
 	int axis = chan->scan_index;
-	__le16 raw_val;
 
 	mutex_lock(&data->mutex);
 	ret = bmc150_accel_set_power_state(data, true);
@@ -632,14 +630,14 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
 	}
 
 	ret = regmap_bulk_read(data->regmap, BMC150_ACCEL_AXIS_TO_REG(axis),
-			       &raw_val, sizeof(raw_val));
+			       &data->regval, sizeof(data->regval));
 	if (ret < 0) {
 		dev_err(dev, "Error reading axis %d\n", axis);
 		bmc150_accel_set_power_state(data, false);
 		mutex_unlock(&data->mutex);
 		return ret;
 	}
-	*val = sign_extend32(le16_to_cpu(raw_val) >> chan->scan_type.shift,
+	*val = sign_extend32(le16_to_cpu(data->regval) >> chan->scan_type.shift,
 			     chan->scan_type.realbits - 1);
 	ret = bmc150_accel_set_power_state(data, false);
 	mutex_unlock(&data->mutex);
@@ -918,7 +916,7 @@ static int bmc150_accel_set_watermark(struct iio_dev *indio_dev, unsigned val)
  * frame data is discarded.
  */
 static int bmc150_accel_fifo_transfer(struct bmc150_accel_data *data,
-				      char *buffer, int samples)
+				      void *buffer, int samples)
 {
 	struct device *dev = regmap_get_device(data->regmap);
 	int sample_length = 3 * 2;
@@ -941,7 +939,6 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
 	struct device *dev = regmap_get_device(data->regmap);
 	int ret, i;
 	u8 count;
-	u16 buffer[BMC150_ACCEL_FIFO_LENGTH * 3];
 	int64_t tstamp;
 	uint64_t sample_period;
 	unsigned int val;
@@ -993,7 +990,7 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
 
 	count = min_t(u8, count, BMC150_ACCEL_FIFO_LENGTH);
 
-	ret = bmc150_accel_fifo_transfer(data, (u8 *)buffer, count);
+	ret = bmc150_accel_fifo_transfer(data, data->fifo_buff, count);
 	if (ret)
 		return ret;
 
@@ -1008,7 +1005,8 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
 
 		j = 0;
 		iio_for_each_active_channel(indio_dev, bit)
-			memcpy(&data->scan.channels[j++], &buffer[i * 3 + bit],
+			memcpy(&data->scan.channels[j++],
+			       &data->fifo_buff[i * 3 + bit],
 			       sizeof(data->scan.channels[0]));
 
 		iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
diff --git a/drivers/iio/accel/bmc150-accel.h b/drivers/iio/accel/bmc150-accel.h
index 9deff256aed5..8f64b24339e4 100644
--- a/drivers/iio/accel/bmc150-accel.h
+++ b/drivers/iio/accel/bmc150-accel.h
@@ -56,6 +56,8 @@ enum bmc150_accel_trigger_id {
 	BMC150_ACCEL_TRIGGERS,
 };
 
+#define BMC150_ACCEL_FIFO_LENGTH		32
+
 struct bmc150_accel_data {
 	struct regmap *regmap;
 	int irq;
@@ -81,6 +83,9 @@ struct bmc150_accel_data {
 		__le16 channels[3];
 		aligned_s64 ts;
 	} scan __aligned(IIO_DMA_MINALIGN);
+	/* DMA-safe buffers for bulk/raw reads */
+	__le16 fifo_buff[BMC150_ACCEL_FIFO_LENGTH * 3] __aligned(IIO_DMA_MINALIGN);
+	__le16 regval __aligned(IIO_DMA_MINALIGN);
 };
 
 int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
-- 
2.43.0

Re: [PATCH v2 2/3] iio: accel: bmc150: use DMA-safe buffers for regmap bulk reads

[Linus Walleij]

On Sat, Aug 15, 2026 at 7:57 PM Yash Suthar <yashsuthar983@gmail.com> wrote:

> The FIFO and read_raw buffers are passed to regmap bulk/raw reads
> ,which is not DMA-safe.Moved them into struct bmc150_accel_data
> after scan, each aligned to IIO_DMA_MINALIGN.
>
> Suggested-by: Jonathan Cameron <jic23@kernel.org>
> Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>

Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij

Re: [PATCH v2 2/3] iio: accel: bmc150: use DMA-safe buffers for regmap bulk reads

[Jonathan Cameron]

On Sat, 15 Aug 2026 23:27:27 +0530
Yash Suthar <yashsuthar983@gmail.com> wrote:

> The FIFO and read_raw buffers are passed to regmap bulk/raw reads
> ,which is not DMA-safe.Moved them into struct bmc150_accel_data

Move the comma up a line.

> after scan, each aligned to IIO_DMA_MINALIGN.
> 
> Suggested-by: Jonathan Cameron <jic23@kernel.org>
> Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>

My main question here is around locking and whether we need
to space all 3 buffers out in a cache line each. That is painful
on some architectures.  If we ensure that DMA to one of these
never overlaps with the CPU accessing a different one, then we can
just mark the first one as IIO_DMA_MINALIGN.

Jonathan

> ---
>  drivers/iio/accel/bmc150-accel-core.c | 14 ++++++--------
>  drivers/iio/accel/bmc150-accel.h      |  5 +++++
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> index 89a475ef9a9b..e8d27fd1be3f 100644
> --- a/drivers/iio/accel/bmc150-accel-core.c
> +++ b/drivers/iio/accel/bmc150-accel-core.c
> @@ -125,7 +125,6 @@
>  #define BMC150_ACCEL_REG_FIFO_CONFIG0		0x30
>  #define BMC150_ACCEL_REG_FIFO_CONFIG1		0x3E
>  #define BMC150_ACCEL_REG_FIFO_DATA		0x3F
> -#define BMC150_ACCEL_FIFO_LENGTH		32
>  
>  enum bmc150_accel_axis {
>  	AXIS_X,
> @@ -622,7 +621,6 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
>  	struct device *dev = regmap_get_device(data->regmap);
>  	int ret;
>  	int axis = chan->scan_index;
> -	__le16 raw_val;
>  
>  	mutex_lock(&data->mutex);
>  	ret = bmc150_accel_set_power_state(data, true);
> @@ -632,14 +630,14 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
>  	}
>  
>  	ret = regmap_bulk_read(data->regmap, BMC150_ACCEL_AXIS_TO_REG(axis),
> -			       &raw_val, sizeof(raw_val));
> +			       &data->regval, sizeof(data->regval));
>  	if (ret < 0) {
>  		dev_err(dev, "Error reading axis %d\n", axis);
>  		bmc150_accel_set_power_state(data, false);
>  		mutex_unlock(&data->mutex);
>  		return ret;
>  	}
> -	*val = sign_extend32(le16_to_cpu(raw_val) >> chan->scan_type.shift,
> +	*val = sign_extend32(le16_to_cpu(data->regval) >> chan->scan_type.shift,
>  			     chan->scan_type.realbits - 1);
>  	ret = bmc150_accel_set_power_state(data, false);
>  	mutex_unlock(&data->mutex);
> @@ -918,7 +916,7 @@ static int bmc150_accel_set_watermark(struct iio_dev *indio_dev, unsigned val)
>   * frame data is discarded.
>   */
>  static int bmc150_accel_fifo_transfer(struct bmc150_accel_data *data,
> -				      char *buffer, int samples)
> +				      void *buffer, int samples)
>  {
>  	struct device *dev = regmap_get_device(data->regmap);
>  	int sample_length = 3 * 2;
> @@ -941,7 +939,6 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
>  	struct device *dev = regmap_get_device(data->regmap);
>  	int ret, i;
>  	u8 count;
> -	u16 buffer[BMC150_ACCEL_FIFO_LENGTH * 3];
>  	int64_t tstamp;
>  	uint64_t sample_period;
>  	unsigned int val;
> @@ -993,7 +990,7 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
>  
>  	count = min_t(u8, count, BMC150_ACCEL_FIFO_LENGTH);
>  
> -	ret = bmc150_accel_fifo_transfer(data, (u8 *)buffer, count);
> +	ret = bmc150_accel_fifo_transfer(data, data->fifo_buff, count);
>  	if (ret)
>  		return ret;
>  
> @@ -1008,7 +1005,8 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
>  
>  		j = 0;
>  		iio_for_each_active_channel(indio_dev, bit)
> -			memcpy(&data->scan.channels[j++], &buffer[i * 3 + bit],
> +			memcpy(&data->scan.channels[j++],
> +			       &data->fifo_buff[i * 3 + bit],
>  			       sizeof(data->scan.channels[0]));
>  
>  		iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
> diff --git a/drivers/iio/accel/bmc150-accel.h b/drivers/iio/accel/bmc150-accel.h
> index 9deff256aed5..8f64b24339e4 100644
> --- a/drivers/iio/accel/bmc150-accel.h
> +++ b/drivers/iio/accel/bmc150-accel.h
> @@ -56,6 +56,8 @@ enum bmc150_accel_trigger_id {
>  	BMC150_ACCEL_TRIGGERS,
>  };
>  
> +#define BMC150_ACCEL_FIFO_LENGTH		32
> +
>  struct bmc150_accel_data {
>  	struct regmap *regmap;
>  	int irq;
> @@ -81,6 +83,9 @@ struct bmc150_accel_data {
>  		__le16 channels[3];
>  		aligned_s64 ts;
>  	} scan __aligned(IIO_DMA_MINALIGN);
> +	/* DMA-safe buffers for bulk/raw reads */
> +	__le16 fifo_buff[BMC150_ACCEL_FIFO_LENGTH * 3] __aligned(IIO_DMA_MINALIGN);
> +	__le16 regval __aligned(IIO_DMA_MINALIGN);

This is potentially a lot of padding that might not be necessary.
What locking protects these?  I'd kind of expect all 3 to be used
under a single lock.  If that's the case and locks are held for all
such usage, then we can just force alignment of the first one.


>  };
>  
>  int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,

Re: [PATCH v2 2/3] iio: accel: bmc150: use DMA-safe buffers for regmap bulk reads

[Yash Suthar]

Hi Jonathan
thanks for review
i agreed with you, earlier i did same as you mentioned see:
https://lore.kernel.org/all/20260814101845.301769-2-yashsuthar983@gmail.com/
but after review from Andy Shevchenko:
https://lore.kernel.org/all/aoApEqsbXp9Pd7Mf@ashevche-desk.local/#t
I agreed and revert the flow for v2, but in doing so I moved
mutex_unlock() before
push.

In v3 will hold mutex for both read and push, single IIO_DMA_MINALIGN on scan
is sufficient, so fifo_buff and regval no longer need separate
__aligned(IIO_DMA_MINALIGN)
Will also replace AXIS_MAX*2 with sizeof(data->scan.channels) and drop
the unused AXIS_MAX.

Sincerely,
Yash Suthar

On Sun, Aug 23, 2026 at 3:36 AM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Sat, 15 Aug 2026 23:27:27 +0530
> Yash Suthar <yashsuthar983@gmail.com> wrote:
>
> > The FIFO and read_raw buffers are passed to regmap bulk/raw reads
> > ,which is not DMA-safe.Moved them into struct bmc150_accel_data
>
> Move the comma up a line.
>
> > after scan, each aligned to IIO_DMA_MINALIGN.
> >
> > Suggested-by: Jonathan Cameron <jic23@kernel.org>
> > Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>
>
> My main question here is around locking and whether we need
> to space all 3 buffers out in a cache line each. That is painful
> on some architectures.  If we ensure that DMA to one of these
> never overlaps with the CPU accessing a different one, then we can
> just mark the first one as IIO_DMA_MINALIGN.
>
> Jonathan
>
> > ---
> >  drivers/iio/accel/bmc150-accel-core.c | 14 ++++++--------
> >  drivers/iio/accel/bmc150-accel.h      |  5 +++++
> >  2 files changed, 11 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> > index 89a475ef9a9b..e8d27fd1be3f 100644
> > --- a/drivers/iio/accel/bmc150-accel-core.c
> > +++ b/drivers/iio/accel/bmc150-accel-core.c
> > @@ -125,7 +125,6 @@
> >  #define BMC150_ACCEL_REG_FIFO_CONFIG0                0x30
> >  #define BMC150_ACCEL_REG_FIFO_CONFIG1                0x3E
> >  #define BMC150_ACCEL_REG_FIFO_DATA           0x3F
> > -#define BMC150_ACCEL_FIFO_LENGTH             32
> >
> >  enum bmc150_accel_axis {
> >       AXIS_X,
> > @@ -622,7 +621,6 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
> >       struct device *dev = regmap_get_device(data->regmap);
> >       int ret;
> >       int axis = chan->scan_index;
> > -     __le16 raw_val;
> >
> >       mutex_lock(&data->mutex);
> >       ret = bmc150_accel_set_power_state(data, true);
> > @@ -632,14 +630,14 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
> >       }
> >
> >       ret = regmap_bulk_read(data->regmap, BMC150_ACCEL_AXIS_TO_REG(axis),
> > -                            &raw_val, sizeof(raw_val));
> > +                            &data->regval, sizeof(data->regval));
> >       if (ret < 0) {
> >               dev_err(dev, "Error reading axis %d\n", axis);
> >               bmc150_accel_set_power_state(data, false);
> >               mutex_unlock(&data->mutex);
> >               return ret;
> >       }
> > -     *val = sign_extend32(le16_to_cpu(raw_val) >> chan->scan_type.shift,
> > +     *val = sign_extend32(le16_to_cpu(data->regval) >> chan->scan_type.shift,
> >                            chan->scan_type.realbits - 1);
> >       ret = bmc150_accel_set_power_state(data, false);
> >       mutex_unlock(&data->mutex);
> > @@ -918,7 +916,7 @@ static int bmc150_accel_set_watermark(struct iio_dev *indio_dev, unsigned val)
> >   * frame data is discarded.
> >   */
> >  static int bmc150_accel_fifo_transfer(struct bmc150_accel_data *data,
> > -                                   char *buffer, int samples)
> > +                                   void *buffer, int samples)
> >  {
> >       struct device *dev = regmap_get_device(data->regmap);
> >       int sample_length = 3 * 2;
> > @@ -941,7 +939,6 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
> >       struct device *dev = regmap_get_device(data->regmap);
> >       int ret, i;
> >       u8 count;
> > -     u16 buffer[BMC150_ACCEL_FIFO_LENGTH * 3];
> >       int64_t tstamp;
> >       uint64_t sample_period;
> >       unsigned int val;
> > @@ -993,7 +990,7 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
> >
> >       count = min_t(u8, count, BMC150_ACCEL_FIFO_LENGTH);
> >
> > -     ret = bmc150_accel_fifo_transfer(data, (u8 *)buffer, count);
> > +     ret = bmc150_accel_fifo_transfer(data, data->fifo_buff, count);
> >       if (ret)
> >               return ret;
> >
> > @@ -1008,7 +1005,8 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
> >
> >               j = 0;
> >               iio_for_each_active_channel(indio_dev, bit)
> > -                     memcpy(&data->scan.channels[j++], &buffer[i * 3 + bit],
> > +                     memcpy(&data->scan.channels[j++],
> > +                            &data->fifo_buff[i * 3 + bit],
> >                              sizeof(data->scan.channels[0]));
> >
> >               iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
> > diff --git a/drivers/iio/accel/bmc150-accel.h b/drivers/iio/accel/bmc150-accel.h
> > index 9deff256aed5..8f64b24339e4 100644
> > --- a/drivers/iio/accel/bmc150-accel.h
> > +++ b/drivers/iio/accel/bmc150-accel.h
> > @@ -56,6 +56,8 @@ enum bmc150_accel_trigger_id {
> >       BMC150_ACCEL_TRIGGERS,
> >  };
> >
> > +#define BMC150_ACCEL_FIFO_LENGTH             32
> > +
> >  struct bmc150_accel_data {
> >       struct regmap *regmap;
> >       int irq;
> > @@ -81,6 +83,9 @@ struct bmc150_accel_data {
> >               __le16 channels[3];
> >               aligned_s64 ts;
> >       } scan __aligned(IIO_DMA_MINALIGN);
> > +     /* DMA-safe buffers for bulk/raw reads */
> > +     __le16 fifo_buff[BMC150_ACCEL_FIFO_LENGTH * 3] __aligned(IIO_DMA_MINALIGN);
> > +     __le16 regval __aligned(IIO_DMA_MINALIGN);
>
> This is potentially a lot of padding that might not be necessary.
> What locking protects these?  I'd kind of expect all 3 to be used
> under a single lock.  If that's the case and locks are held for all
> such usage, then we can just force alignment of the first one.
>
>
> >  };
> >
> >  int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
>

[PATCH v2 3/3] iio: accel: bmc150: use iio_push_to_buffers_with_ts()

[Yash Suthar]

Replace deprecated iio_push_to_buffers_with_timestamp() with
iio_push_to_buffers_with_ts() to allow source size runtime checks.

Suggested-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>
---
 drivers/iio/accel/bmc150-accel-core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
index e8d27fd1be3f..b6d67965b984 100644
--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -1009,8 +1009,8 @@ static int __bmc150_accel_fifo_flush(struct iio_dev *indio_dev,
 			       &data->fifo_buff[i * 3 + bit],
 			       sizeof(data->scan.channels[0]));
 
-		iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
-						   tstamp);
+		iio_push_to_buffers_with_ts(indio_dev, &data->scan,
+					    sizeof(data->scan), tstamp);
 
 		tstamp += sample_period;
 	}
@@ -1194,8 +1194,8 @@ static irqreturn_t bmc150_accel_trigger_handler(int irq, void *p)
 	if (ret < 0)
 		goto err_read;
 
-	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
-					   pf->timestamp);
+	iio_push_to_buffers_with_ts(indio_dev, &data->scan,
+				    sizeof(data->scan), pf->timestamp);
 err_read:
 	iio_trigger_notify_done(indio_dev->trig);
 
-- 
2.43.0

Re: [PATCH v2 3/3] iio: accel: bmc150: use iio_push_to_buffers_with_ts()

[Linus Walleij]

On Sat, Aug 15, 2026 at 7:57 PM Yash Suthar <yashsuthar983@gmail.com> wrote:

> Replace deprecated iio_push_to_buffers_with_timestamp() with
> iio_push_to_buffers_with_ts() to allow source size runtime checks.
>
> Suggested-by: David Lechner <dlechner@baylibre.com>
> Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>

Reviewed-by: Linus Walleij <linusw@kernel.org>

Yours,
Linus Walleij

Re: [PATCH v2 0/3] iio: accel: bmc150: DMA-safe buffers and use iio_push_to_buffers_with_ts()

[Gabriel Rondon]

On Sat, 15 Aug 2026 23:27:25 +0530, Yash Suthar wrote:
> The trigger path used a plain s16 buffer while the FIFO path already had
> a properly typed scan member (__le16 + aligned timestamp). Those two
> buffers did the same job, and s16 does not represent little-endian data.

Built the series on top of current iio/togreg with gcc 13.3, x86_64
allmodconfig and W=1: the three bmc150 objects (core, i2c, spi) compile
cleanly with no new warnings.

I also used it as the base for v4 of my bmc150 series (event-enable
race fix + guard(mutex) conversion), which is rebased on top of these
patches:
https://lore.kernel.org/linux-iio/20260816234231.14168-1-grondon@gmail.com/

Gabriel