[PATCH v2] iio: imu: inv_icm42600: add buffer hwfifo watermark attributes

[PATCH v2] iio: imu: inv_icm42600: add buffer hwfifo watermark attributes

[Jean-Baptiste Maneyrol via B4 Relay]

From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Add hwfifo_watermark/min/max/enabled buffer attributes.
Hardware FIFO is always enabled and used.

Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
---
Changes in v2:
- Delete trailing comma after NULL terminator
- Link to v1: https://patch.msgid.link/20260623-inv-icm42600-add-buffer-hwfifo_attributes-v1-1-d190800e60de@tdk.com

To: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
To: Jonathan Cameron <jic23@kernel.org>
To: David Lechner <dlechner@baylibre.com>
To: Nuno Sá <nuno.sa@analog.com>
To: Andy Shevchenko <andy@kernel.org>
Cc: linux-iio@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/iio/imu/inv_icm42600/inv_icm42600.h        |  2 ++
 drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c  |  5 +--
 drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c | 37 ++++++++++++++++++++++
 drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.h |  1 +
 drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c   |  5 +--
 5 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600.h b/drivers/iio/imu/inv_icm42600/inv_icm42600.h
index c8b48a5c5ed0..7c9b63584a05 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600.h
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600.h
@@ -354,6 +354,8 @@ struct inv_icm42600_sensor_state {
 		cpu_to_le16((_wm) & GENMASK(11, 0))
 /* FIFO is 2048 bytes, let 12 samples for reading latency */
 #define INV_ICM42600_FIFO_WATERMARK_MAX			(2048 - 12 * 16)
+/* INV_ICM42600_FIFO_WATERMARK_MAX / 8 = 232 */
+#define INV_ICM42600_FIFO_WATERMARK_MAX_SAMPLES		232
 
 #define INV_ICM42600_REG_INT_CONFIG1			0x0064
 #define INV_ICM42600_INT_CONFIG1_TPULSE_DURATION	BIT(6)
diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
index 532d5fdffaf8..1ab73953bef6 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_accel.c
@@ -1186,8 +1186,9 @@ struct iio_dev *inv_icm42600_accel_init(struct inv_icm42600_state *st)
 	indio_dev->num_channels = ARRAY_SIZE(inv_icm42600_accel_channels);
 	indio_dev->available_scan_masks = inv_icm42600_accel_scan_masks;
 
-	ret = devm_iio_kfifo_buffer_setup(dev, indio_dev,
-					  &inv_icm42600_buffer_ops);
+	ret = devm_iio_kfifo_buffer_setup_ext(dev, indio_dev,
+					      &inv_icm42600_buffer_ops,
+					      inv_icm42600_buffer_attrs);
 	if (ret)
 		return ERR_PTR(ret);
 
diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c
index 68a395758031..f7d41584b693 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c
@@ -10,10 +10,12 @@
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/delay.h>
+#include <linux/stringify.h>
 
 #include <linux/iio/buffer.h>
 #include <linux/iio/common/inv_sensors_timestamp.h>
 #include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
 
 #include "inv_icm42600.h"
 #include "inv_icm42600_buffer.h"
@@ -437,6 +439,41 @@ const struct iio_buffer_setup_ops inv_icm42600_buffer_ops = {
 	.postdisable = inv_icm42600_buffer_postdisable,
 };
 
+static ssize_t inv_icm42600_buffer_get_watermark(struct device *dev,
+						 struct device_attribute *attr,
+						 char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct inv_icm42600_state *st = iio_device_get_drvdata(indio_dev);
+	unsigned int wm;
+
+	guard(mutex)(&st->lock);
+
+	if (indio_dev == st->indio_accel)
+		wm = st->fifo.watermark.eff_accel;
+	else if (indio_dev == st->indio_gyro)
+		wm = st->fifo.watermark.eff_gyro;
+	else
+		return -EINVAL;
+
+	return sysfs_emit(buf, "%u\n", wm);
+}
+
+IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_watermark_min, "1");
+IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_watermark_max,
+			     __stringify(INV_ICM42600_FIFO_WATERMARK_MAX_SAMPLES));
+static IIO_DEVICE_ATTR(hwfifo_watermark, 0444, inv_icm42600_buffer_get_watermark,
+		       NULL, 0);
+IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_enabled, "1");
+
+const struct iio_dev_attr *inv_icm42600_buffer_attrs[] = {
+	&iio_dev_attr_hwfifo_watermark_min,
+	&iio_dev_attr_hwfifo_watermark_max,
+	&iio_dev_attr_hwfifo_watermark,
+	&iio_dev_attr_hwfifo_enabled,
+	NULL
+};
+
 int inv_icm42600_buffer_fifo_read(struct inv_icm42600_state *st,
 				  unsigned int max)
 {
diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.h b/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.h
index ffca4da1e249..522e158accc9 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.h
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.h
@@ -79,6 +79,7 @@ ssize_t inv_icm42600_fifo_decode_packet(const void *packet, const void **accel,
 					const void **timestamp, unsigned int *odr);
 
 extern const struct iio_buffer_setup_ops inv_icm42600_buffer_ops;
+extern const struct iio_dev_attr *inv_icm42600_buffer_attrs[];
 
 int inv_icm42600_buffer_init(struct inv_icm42600_state *st);
 
diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
index 11339ddf1da3..7d4f6701f124 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_gyro.c
@@ -772,8 +772,9 @@ struct iio_dev *inv_icm42600_gyro_init(struct inv_icm42600_state *st)
 	indio_dev->available_scan_masks = inv_icm42600_gyro_scan_masks;
 	indio_dev->setup_ops = &inv_icm42600_buffer_ops;
 
-	ret = devm_iio_kfifo_buffer_setup(dev, indio_dev,
-					  &inv_icm42600_buffer_ops);
+	ret = devm_iio_kfifo_buffer_setup_ext(dev, indio_dev,
+					      &inv_icm42600_buffer_ops,
+					      inv_icm42600_buffer_attrs);
 	if (ret)
 		return ERR_PTR(ret);
 

---
base-commit: cc746297b23e89bd5df9f91f3a0ca209e8991763
change-id: 20260622-inv-icm42600-add-buffer-hwfifo_attributes-aced0415e341

Best regards,
--  
Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Re: [PATCH v2] iio: imu: inv_icm42600: add buffer hwfifo watermark attributes

[Andy Shevchenko]

On Wed, Jun 24, 2026 at 10:25:46AM +0200, Jean-Baptiste Maneyrol via B4 Relay wrote:

> Add hwfifo_watermark/min/max/enabled buffer attributes.
> Hardware FIFO is always enabled and used.

...

> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c

>  #include <linux/pm_runtime.h>
>  #include <linux/regmap.h>
>  #include <linux/delay.h>
> +#include <linux/stringify.h>
>  
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/common/inv_sensors_timestamp.h>
>  #include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>

Since I have another comment below, I would note that the list of inclusions
perhaps needs a preparatory patch to be sorted and regrouped a bit:

<linux/*.h>
...blank line...
<linux/iio/*.h>
...blank line...
<linux/iio/common/inv_*.h> // since it's quite custom but world visible header.
...blank line...
"*.h"

...

> +IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_watermark_min, "1");
> +IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_watermark_max,
> +			     __stringify(INV_ICM42600_FIFO_WATERMARK_MAX_SAMPLES));
> +static IIO_DEVICE_ATTR(hwfifo_watermark, 0444, inv_icm42600_buffer_get_watermark,
> +		       NULL, 0);

So, why not IIO_DEVICE_ATTR_RO()?

> +IIO_STATIC_CONST_DEVICE_ATTR(hwfifo_enabled, "1");

-- 
With Best Regards,
Andy Shevchenko