iio: flow: Sensirion SLF3S liquid flow sensor

Add a new IIO channel type for liquid volumetric flow sensors. The unit exposed via the standard _scale attribute is cubic metres per second (m^3/s), following the SI convention used by the other IIO channel types.

Update iio-core's name table, the iio_event_monitor whitelist and the sysfs-bus-iio ABI document to match. The new _scale attribute is folded into the existing shared _scale block; only the per-type _raw needs a fresh entry.

Signed-off-by Wadim Mueller <[email protected]>

---

Document the bindings for the Sensirion SLF3S family of digital liquid-flow sensors on I2C. The family currently covers the SLF3S-0600F, SLF3S-1300F and SLF3S-4000B variants.

All variants share the same register map and differ only in the flow scale factor and the calibrated measurement range, which the driver reads back from the product-information register. Since that lookup is needed in any case, a fallback compatible would buy nothing, so each variant gets its own compatible without a fallback. A future drop-in compatible part can then claim one of these compatibles and work on kernels that do not know its product ID yet.

The active calibration medium (water / IPA) is runtime-switchable via the in_volumeflow_medium sysfs attribute and therefore not a DT property.

Signed-off-by Wadim Mueller <[email protected]>

---
 .../bindings/iio/flow/sensirion,slf3s.yaml    | 55 +++++++++++++++++++
 MAINTAINERS                                   |  7 +++
 2 files changed, 62 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/flow/sensirion,slf3s.yaml

Documentation/devicetree/bindings/iio/flow/sensirion,slf3s.yaml new file +55 -0

new file mode 100644
index 000000000000..79718f4f98bd
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/flow/sensirion,slf3s.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Sensirion SLF3S liquid flow sensor
+
+maintainers:
+  - Wadim Mueller <[email protected]>
+
+description:
+  Family of digital liquid-flow sensors from Sensirion with I2C interface. All
+  family members share the same register map; sub-types differ only in the flow
+  scale factor and the calibrated measurement range. The sub-type can be
+  identified from the product-information register.
+
+properties:
+  compatible:
+    enum:
+      - sensirion,slf3s-0600f
+      - sensirion,slf3s-1300f
+      - sensirion,slf3s-4000b
+
+  reg:
+    maxItems: 1
+
+  vdd-supply: true
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        flow-sensor@8 {
+            compatible = "sensirion,slf3s-0600f";
+            reg = <0x08>;
+            vdd-supply = <&reg_3v3>;
+            interrupt-parent = <&gpio0>;
+            interrupts = <0 IRQ_TYPE_EDGE_RISING>;
+        };
+    };

MAINTAINERS +7 -0

index ce020ded5fd3..497492825f70 100644
@@ -24583,6 +24583,13 @@ S:	Maintained
 F:	Documentation/ABI/testing/sysfs-bus-iio-chemical-sgp40
 F:	drivers/iio/chemical/sgp40.c
 
+SENSIRION SLF3S LIQUID FLOW SENSOR DRIVER
+M:	Wadim Mueller <[email protected]>
+R:	Maxwell Doose <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/flow/sensirion,slf3s.yaml
+
 SENSIRION SPS30 AIR POLLUTION SENSOR DRIVER
 M:	Tomasz Duszynski <[email protected]>
 S:	Maintained

Document the bindings for the Sensirion SLF3S family of digital liquid-flow sensors on I2C. The family currently covers the SLF3S-0600F, SLF3S-1300F and SLF3S-4000B variants.

All variants share the same register map and differ only in the flow scale factor and the calibrated measurement range, which the driver reads back from the product-information register. Since that lookup is needed in any case, a fallback compatible would buy nothing, so each variant gets its own compatible without a fallback. A future drop-in compatible part can then claim one of these compatibles and work on kernels that do not know its product ID yet.

The active calibration medium (water / IPA) is runtime-switchable via the in_volumeflow_medium sysfs attribute and therefore not a DT property.

Signed-off-by Wadim Mueller <[email protected]>

---
 .../bindings/iio/flow/sensirion,slf3s.yaml    | 55 +++++++++++++++++++
 MAINTAINERS                                   |  7 +++
 2 files changed, 62 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/flow/sensirion,slf3s.yaml

Extend the IIO_VAL_DECIMAL64_* family with a femto-scaled variant (scale 15), following the existing MILLI/MICRO/NANO/PICO pattern. Both the read formatting path in __iio_format_value() and the write parsing path in iio_write_channel_info() (via kstrtodec64()) already derive their scale from "type - IIO_VAL_DECIMAL64_BASE", so the new type only needs to be added to the respective switch cases.

This is needed by drivers reporting very small SI quantities where the existing pico scale loses precision. For example the Sensirion SLF3S liquid flow sensor reports its volume-flow scale in m^3/s, where the SLF3S-0600F scale is ~1.667e-12 m^3/s: at pico scale only a single significant digit survives, whereas femto scale preserves the full sensor resolution.

Signed-off-by Wadim Mueller <[email protected]>

Reviewed-by Rodrigo Alencar <[email protected]>

---
 drivers/iio/industrialio-core.c | 2 ++
 include/linux/iio/types.h       | 1 +
 2 files changed, 3 insertions(+)

drivers/iio/industrialio-core.c +2 -0

index 37cf2817b3d0..767a7794624a 100644
@@ -715,6 +715,7 @@ static ssize_t __iio_format_value(char *buf, size_t offset, unsigned int type,
 	case IIO_VAL_DECIMAL64_MICRO:
 	case IIO_VAL_DECIMAL64_NANO:
 	case IIO_VAL_DECIMAL64_PICO:
+	case IIO_VAL_DECIMAL64_FEMTO:
 	{
 		int scale = type - IIO_VAL_DECIMAL64_BASE;
 		s64 frac;

@@ -1032,6 +1033,7 @@ static ssize_t iio_write_channel_info(struct device *dev,
 		case IIO_VAL_DECIMAL64_MICRO:
 		case IIO_VAL_DECIMAL64_NANO:
 		case IIO_VAL_DECIMAL64_PICO:
+		case IIO_VAL_DECIMAL64_FEMTO:
 			dec_scale = type - IIO_VAL_DECIMAL64_BASE;
 			fallthrough;
 		case IIO_VAL_INT_64:

include/linux/iio/types.h +0 -0

index 924ac9dc6893..d8944c9e5e90 100644

Quoted 51 lines · Wadim Mueller

Extend the IIO_VAL_DECIMAL64_* family with a femto-scaled variant (scale 15), following the existing MILLI/MICRO/NANO/PICO pattern. Both the read formatting path in __iio_format_value() and the write parsing path in iio_write_channel_info() (via kstrtodec64()) already derive their scale from "type - IIO_VAL_DECIMAL64_BASE", so the new type only needs to be added to the respective switch cases.

This is needed by drivers reporting very small SI quantities where the existing pico scale loses precision. For example the Sensirion SLF3S liquid flow sensor reports its volume-flow scale in m^3/s, where the SLF3S-0600F scale is ~1.667e-12 m^3/s: at pico scale only a single significant digit survives, whereas femto scale preserves the full sensor resolution.

Signed-off-by Wadim Mueller <[email protected]>

Reviewed-by Rodrigo Alencar <[email protected]>

---
 drivers/iio/industrialio-core.c | 2 ++
 include/linux/iio/types.h       | 1 +
 2 files changed, 3 insertions(+)

drivers/iio/industrialio-core.c +2 -0

index 37cf2817b3d0..767a7794624a 100644
@@ -715,6 +715,7 @@ static ssize_t __iio_format_value(char *buf, size_t offset, unsigned int type,
 	case IIO_VAL_DECIMAL64_MICRO:
 	case IIO_VAL_DECIMAL64_NANO:
 	case IIO_VAL_DECIMAL64_PICO:
+	case IIO_VAL_DECIMAL64_FEMTO:
 	{
 		int scale = type - IIO_VAL_DECIMAL64_BASE;
 		s64 frac;

@@ -1032,6 +1033,7 @@ static ssize_t iio_write_channel_info(struct device *dev,
 		case IIO_VAL_DECIMAL64_MICRO:
 		case IIO_VAL_DECIMAL64_NANO:
 		case IIO_VAL_DECIMAL64_PICO:
+		case IIO_VAL_DECIMAL64_FEMTO:
 			dec_scale = type - IIO_VAL_DECIMAL64_BASE;
 			fallthrough;
 		case IIO_VAL_INT_64:

include/linux/iio/types.h +1 -0

index 924ac9dc6893..d8944c9e5e90 100644
@@ -42,6 +42,7 @@ enum iio_event_info {
 #define IIO_VAL_DECIMAL64_MICRO		(IIO_VAL_DECIMAL64_BASE + 6)
 #define IIO_VAL_DECIMAL64_NANO		(IIO_VAL_DECIMAL64_BASE + 9)
 #define IIO_VAL_DECIMAL64_PICO		(IIO_VAL_DECIMAL64_BASE + 12)
+#define IIO_VAL_DECIMAL64_FEMTO		(IIO_VAL_DECIMAL64_BASE + 15)
 

include/linux/iio/types.h enum iio_event_info { · line 48

Quoted 2 lines

include/linux/iio/types.h +0 -0

 static inline s64 iio_val_s64_compose(s32 val0, s32 val1)
 {  

Would be nice to add this to drivers/iio/test/iio-test-format.c too.

Hello,

drivers/iio/flow/slf3s.c line 32

Quoted 3 lines · Wadim Mueller

drivers/iio/flow/slf3s.c new file +2 -0

+#include <linux/i2c.h>
[...]
+#include <linux/mod_devicetable.h>  

<linux/i2c.h> already makes sure that of_device_id and i2c_device_id are available and <linux/mod_devicetable.h> will go away soon.

So please drop the latter #include.

Best regards
Uwe

Add a driver for the Sensirion SLF3S family of digital liquid-flow sensors on I2C. Currently supported variants are SLF3S-0600F, SLF3S-1300F and SLF3S-4000B; they share the same register map and differ only in flow-scale factor and calibrated measurement range. The variant (and therefore the scale) is auto-detected from the product-information register at probe time; a sensor reporting an unknown sub-type falls back to the variant named in the device tree / I2C table, so a drop-in replacement part keeps working on a kernel that does not know its sub-type yet.

Quoted 10 lines · Wadim Mueller

Add a driver for the Sensirion SLF3S family of digital liquid-flow sensors on I2C. Currently supported variants are SLF3S-0600F, SLF3S-1300F and SLF3S-4000B; they share the same register map and differ only in flow-scale factor and calibrated measurement range. The variant (and therefore the scale) is auto-detected from the product-information register at probe time; a sensor reporting an unknown sub-type falls back to the variant named in the device tree / I2C table, so a drop-in replacement part keeps working on a kernel that does not know its sub-type yet.

...

drivers/iio/flow/slf3s.c line 165

Quoted 11 lines

drivers/iio/flow/slf3s.c new file +11 -0

+static bool slf3s_crc_valid(const struct slf3s_data *sf, const u8 *block)
+{
+	return crc8(sf->crc_table, block, 2, SLF3S_CRC8_INIT) == block[2];
+}
+
+/*
+ * Read the product-info block and pick the matching variant.  The
+ * sub-type byte returned by the sensor is the source of truth; a
+ * DT-supplied compatible only seeds an initial guess and is overridden
+ * on mismatch (with an informational message so misconfigured device
+ * trees are easy to spot).  

In the past, Jonathan has always argued that the devicetree should be trusted more than what the device self-reports. This seems a departure from that. Why are we making an exception here?

We have to trust that the devicetree is correct for everything else that can't self-detect anyway.

Hi all,

this series adds a driver for the Sensirion SLF3S family of I2C liquid flow sensors (SLF3S-0600F / -1300F / -4000B) and a new IIO_VOLUMEFLOW channel type.

First of all: sorry for the noise. Patch 4/4 of v5 never made it to the list or to patchwork - it got lost on the way out from the machine I sent v5 from, as Jonathan noticed:

https://lore.kernel.org/linux-iio/20260720032927.14fc4f9f@jic23-huawei/

So this v6 is mostly a resend of v5 with the driver patch actually included, plus the binding change we converged on in the meantime. The driver changes that were listed in the v5 changelog are repeated below, since nobody got to see them.

The series is based on iio.git testing, which already contains Rodrigo Alencar's IIO_VAL_DECIMAL64_* core formatting work; patch 3/4 adds the IIO_VAL_DECIMAL64_FEMTO format type on top of it.

Changes since v5
----------------
* 4/4 is included this time - v5 only had 1-3 on the list
* dt-bindings: dropped the fallback compatible entirely; each variant now has its own compatible, per the conclusion of the v4 discussion between Krzysztof and Jonathan. Since the driver has to look at the product-information register anyway, a fallback buys nothing, while separate compatibles let a future drop-in part claim a known compatible and work on older kernels
* dt-bindings: dropped Krzysztof's Reviewed-by, since the compatible schema changed
* dt-bindings: commit message and example updated accordingly
* driver: reworded the slf3s_detect_variant() comment and the commit message, which referred to the now-gone fallback compatible. The behaviour is unchanged: an unknown sub-type still falls back to the variant named in the device tree / I2C table
* rebased onto current iio.git testing

Changes since v4 (from the v5 posting, repeated because 4/4 was lost)
---------------------------------------------------------------------
* driver: include err.h for PTR_ERR() and math.h for struct s32_fract, per Andy
* driver: fold the per-variant scale_num/scale_den pair into a struct s32_fract, per Andy
* driver: add enum slf3s_variant_id and use it for the variant table and the I2C/OF match tables instead of bare indices, per Andy
* driver: slf3s_send_cmd(): drop the "at_least 2" parameter annotation, decouple the ret assignment from its declaration and check errors first, per Andy
* driver: use sizeof() instead of ARRAY_SIZE() for the measurement byte buffer, per Andy
* driver: parenthesise the (FEMTO / MILLI) factor so it folds into a single constant multiplication, per Andy
* driver: derive the temperature scale from MILLIDEGREE_PER_DEGREE instead of a bare 1000, per Andy
* driver: checked the struct slf3s_data layout (re Andy's pahole question): the non-pointer members total 260 bytes, so one 4-byte hole remains for any member order; left as is
* driver: drop the inline comment on the mutex that duplicated the kernel-doc, per Jonathan (checkpatch still moans about it)
* driver: fix the duplicated argument in the DT/sensor variant mismatch dev_info(), per Jonathan
* driver: reformat the i2c_device_id/of_device_id tables to one member per line, per Jonathan
* MAINTAINERS: updated Maxwell's address in the R: entry to [email protected], as he requested on the v4 thread

The signaling-flags word (air-in-line / high-flow / smoothing status) in each measurement frame is intentionally not read; exposing it can be a later follow-up.

v5: https://lore.kernel.org/linux-iio/[email protected]/
v4: https://lore.kernel.org/linux-iio/[email protected]/

Thanks,
Wadim

Wadim Mueller (4):
iio: types: add IIO_VOLUMEFLOW channel type
dt-bindings: iio: flow: add Sensirion SLF3S liquid flow sensor
iio: core: add IIO_VAL_DECIMAL64_FEMTO format type
iio: flow: add Sensirion SLF3S liquid flow sensor driver

 Documentation/ABI/testing/sysfs-bus-iio       |  11 +
 Documentation/ABI/testing/sysfs-bus-iio-flow  |  21 +
 .../bindings/iio/flow/sensirion,slf3s.yaml    |  55 ++
 MAINTAINERS                                   |   8 +
 drivers/iio/Kconfig                           |   1 +
 drivers/iio/Makefile                          |   1 +
 drivers/iio/flow/Kconfig                      |  22 +
 drivers/iio/flow/Makefile                     |   7 +
 drivers/iio/flow/slf3s.c                      | 543 ++++++++++++++++++
 drivers/iio/industrialio-core.c               |   3 +
 include/linux/iio/types.h                     |   1 +
 include/uapi/linux/iio/types.h                |   1 +
 tools/iio/iio_event_monitor.c                 |   2 +
 13 files changed, 676 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-flow
 create mode 100644 Documentation/devicetree/bindings/iio/flow/sensirion,slf3s.yaml
 create mode 100644 drivers/iio/flow/Kconfig
 create mode 100644 drivers/iio/flow/Makefile
 create mode 100644 drivers/iio/flow/slf3s.c

base-commit: e0484d62e8e1cff75b210938be835ea6221bda59

Quoted 5 lines · On Tue, 28 Jul 2026 23:49:39 +0200 Wadim Mueller <[email protected]> wrote:

Hi all,

this series adds a driver for the Sensirion SLF3S family of I2C liquid flow sensors (SLF3S-0600F / -1300F / -4000B) and a new IIO_VOLUMEFLOW channel type.

I'm going to apply this now, but as it will be in my testing branch (which I do rebase) for a few days fully welcome any additional comments or tags.

Applied to the testing branch of iio.git

Thanks,

Jonathan

Quoted 101 lines

First of all: sorry for the noise. Patch 4/4 of v5 never made it to the list or to patchwork - it got lost on the way out from the machine I sent v5 from, as Jonathan noticed:

https://lore.kernel.org/linux-iio/20260720032927.14fc4f9f@jic23-huawei/

So this v6 is mostly a resend of v5 with the driver patch actually included, plus the binding change we converged on in the meantime. The driver changes that were listed in the v5 changelog are repeated below, since nobody got to see them.

The series is based on iio.git testing, which already contains Rodrigo Alencar's IIO_VAL_DECIMAL64_* core formatting work; patch 3/4 adds the IIO_VAL_DECIMAL64_FEMTO format type on top of it.

Changes since v5
----------------
* 4/4 is included this time - v5 only had 1-3 on the list
* dt-bindings: dropped the fallback compatible entirely; each variant now has its own compatible, per the conclusion of the v4 discussion between Krzysztof and Jonathan. Since the driver has to look at the product-information register anyway, a fallback buys nothing, while separate compatibles let a future drop-in part claim a known compatible and work on older kernels
* dt-bindings: dropped Krzysztof's Reviewed-by, since the compatible schema changed
* dt-bindings: commit message and example updated accordingly
* driver: reworded the slf3s_detect_variant() comment and the commit message, which referred to the now-gone fallback compatible. The behaviour is unchanged: an unknown sub-type still falls back to the variant named in the device tree / I2C table
* rebased onto current iio.git testing

Changes since v4 (from the v5 posting, repeated because 4/4 was lost)
---------------------------------------------------------------------
* driver: include err.h for PTR_ERR() and math.h for struct s32_fract, per Andy
* driver: fold the per-variant scale_num/scale_den pair into a struct s32_fract, per Andy
* driver: add enum slf3s_variant_id and use it for the variant table and the I2C/OF match tables instead of bare indices, per Andy
* driver: slf3s_send_cmd(): drop the "at_least 2" parameter annotation, decouple the ret assignment from its declaration and check errors first, per Andy
* driver: use sizeof() instead of ARRAY_SIZE() for the measurement byte buffer, per Andy
* driver: parenthesise the (FEMTO / MILLI) factor so it folds into a single constant multiplication, per Andy
* driver: derive the temperature scale from MILLIDEGREE_PER_DEGREE instead of a bare 1000, per Andy
* driver: checked the struct slf3s_data layout (re Andy's pahole question): the non-pointer members total 260 bytes, so one 4-byte hole remains for any member order; left as is
* driver: drop the inline comment on the mutex that duplicated the kernel-doc, per Jonathan (checkpatch still moans about it)
* driver: fix the duplicated argument in the DT/sensor variant mismatch dev_info(), per Jonathan
* driver: reformat the i2c_device_id/of_device_id tables to one member per line, per Jonathan
* MAINTAINERS: updated Maxwell's address in the R: entry to [email protected], as he requested on the v4 thread

The signaling-flags word (air-in-line / high-flow / smoothing status) in each measurement frame is intentionally not read; exposing it can be a later follow-up.

v5: https://lore.kernel.org/linux-iio/[email protected]/
v4: https://lore.kernel.org/linux-iio/[email protected]/

Thanks,
Wadim

Wadim Mueller (4):
iio: types: add IIO_VOLUMEFLOW channel type
dt-bindings: iio: flow: add Sensirion SLF3S liquid flow sensor
iio: core: add IIO_VAL_DECIMAL64_FEMTO format type
iio: flow: add Sensirion SLF3S liquid flow sensor driver

 Documentation/ABI/testing/sysfs-bus-iio       |  11 +
 Documentation/ABI/testing/sysfs-bus-iio-flow  |  21 +
 .../bindings/iio/flow/sensirion,slf3s.yaml    |  55 ++
 MAINTAINERS                                   |   8 +
 drivers/iio/Kconfig                           |   1 +
 drivers/iio/Makefile                          |   1 +
 drivers/iio/flow/Kconfig                      |  22 +
 drivers/iio/flow/Makefile                     |   7 +
 drivers/iio/flow/slf3s.c                      | 543 ++++++++++++++++++
 drivers/iio/industrialio-core.c               |   3 +
 include/linux/iio/types.h                     |   1 +
 include/uapi/linux/iio/types.h                |   1 +
 tools/iio/iio_event_monitor.c                 |   2 +
 13 files changed, 676 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-flow
 create mode 100644 Documentation/devicetree/bindings/iio/flow/sensirion,slf3s.yaml
 create mode 100644 drivers/iio/flow/Kconfig
 create mode 100644 drivers/iio/flow/Makefile
 create mode 100644 drivers/iio/flow/slf3s.c

base-commit: e0484d62e8e1cff75b210938be835ea6221bda59