[PATCH v4 0/2] hwmon: Add Murata D1U74T-W PSU driver

[PATCH v4 0/2] hwmon: Add Murata D1U74T-W PSU driver

[Abdurrahman Hussain]

This series adds a PMBus driver for the Murata D1U74T-W AC/DC power
supply unit, used in some Open Compute Project platforms.

The PSU is PMBus-compliant and uses the linear data format. The driver
exposes:

  - input/output voltage, current and power telemetry,
  - three temperature sensors,
  - dual fan tachometer monitoring,

through the standard hwmon/pmbus sysfs interface. Probe verifies the
PMBUS_MFR_ID and PMBUS_MFR_MODEL fields before binding so the driver
only attaches to actual D1U74T-W hardware.

Patch 1 adds the compatible string to trivial-devices.yaml. The
binding declares only compatible and reg (no regulators, no supplies),
so a standalone binding file is not warranted.

Patch 2 adds the driver, hwmon documentation, Kconfig/Makefile entries
and MAINTAINERS section.

Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
Changes in v4:
- Patch 1: rewrite the commit message to describe the hardware (the
  D1U74T-W series of 1U CRPS-185 / OCP M-CRPS AC/DC PSUs, dual 12 V
  outputs, internal variable-speed fan, PMBus 1.2 on I2C) rather
  than the binding format, per Krzysztof Kozlowski's review of v3.
- Patch 2: update the Datasheet line in
  Documentation/hwmon/d1u74t.rst from "Only available under NDA" to
  reflect that the D1U74T-W series datasheets are publicly available
  on Murata's website.
- Link to v3: https://patch.msgid.link/20260513-d1u74t-v3-0-27bcd6852c45@nexthop.ai

Changes in v3 (addresses the sashiko automated review):
- Patch 2: move the new MAINTAINERS entry into the correct
  alphabetical position in the M section (between MULTIPLEXER
  SUBSYSTEM and MUSB MULTIPOINT) instead of leaving it wedged
  between CRPS DRIVER and CRYPTO API.
- Patch 2: rewrite the sysfs-entries table in
  Documentation/hwmon/d1u74t.rst to match the attributes the chip
  actually exposes. The previous table listed the PMBus-spec
  maximal set (crit/lcrit/max/min for in1/in2, crit for temp,
  max/max_alarm for curr1, etc.) but the chip only implements a
  subset; pmbus_core consequently only creates a subset of attrs.
  Cross-checked against two D1U74T-W units, both expose the same
  attribute set. Also fixes the in2_* descriptions that incorrectly
  referred to "input voltage" rather than output voltage (in2 is
  vout1).
- Patch 2: use dev_err_probe() for the MFR_ID-mismatch error path
  in d1u74t_probe(), matching the surrounding error-handling style.
- Patch 2: gate the MFR_MODEL strncmp() on rc >= 8 so a short
  block-read response cannot make the comparison read stale bytes
  left over from the previous MFR_ID read into the same buffer.
- Patch 1 is unchanged from v2.
- Link to v2: https://patch.msgid.link/20260512-d1u74t-v2-0-431d00fbb1c4@nexthop.ai

Changes in v2:
- Patch 1: move the binding into trivial-devices.yaml rather than
  carrying a standalone murata,d1u74t.yaml. The device only declares
  compatible and reg, with no regulators or supplies, so the
  standalone binding was not warranted (Conor Dooley review).
- Patch 2: fix the d1u74t.rst title underline (was 18 '=' chars under
  a 20-char title, docutils warning from the kernel test robot).
- Link to v1: https://patch.msgid.link/20260511-d1u74t-v1-0-623c2bc1532a@nexthop.ai

To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
To: Abdurrahman Hussain <abdurrahman@nexthop.ai>
To: Guenter Roeck <linux@roeck-us.net>
To: Jonathan Corbet <corbet@lwn.net>
To: Shuah Khan <skhan@linuxfoundation.org>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-hwmon@vger.kernel.org
Cc: linux-doc@vger.kernel.org

---
Abdurrahman Hussain (2):
      dt-bindings: trivial-devices: Add Murata D1U74T PSU
      hwmon: (pmbus/d1u74t) Add Murata D1U74T PSU driver

 .../devicetree/bindings/trivial-devices.yaml       |  2 +
 Documentation/hwmon/d1u74t.rst                     | 81 ++++++++++++++++++++
 Documentation/hwmon/index.rst                      |  1 +
 MAINTAINERS                                        |  7 ++
 drivers/hwmon/pmbus/Kconfig                        |  9 +++
 drivers/hwmon/pmbus/Makefile                       |  1 +
 drivers/hwmon/pmbus/d1u74t.c                       | 86 ++++++++++++++++++++++
 7 files changed, 187 insertions(+)
---
base-commit: 1f63dd8ca0dc05a8272bb8155f643c691d29bb11
change-id: 20260511-d1u74t-c0cba8f1c344

Best regards,
--  
Abdurrahman Hussain <abdurrahman@nexthop.ai>

[PATCH v4 1/2] dt-bindings: trivial-devices: Add Murata D1U74T PSU

[Abdurrahman Hussain]

The Murata D1U74T-W series are hot-pluggable 1U AC/DC front-end
power supplies in the Intel CRPS-185 / OCP M-CRPS form factor.
Each variant delivers a 12 V main output plus a 12 V standby output
from a wide AC input (90-264 Vac) or HVDC supply, and includes an
internal variable-speed cooling fan and on-board voltage, current,
power, fan-speed, and temperature telemetry.

The host-side digital interface is a PMBus 1.2 port on I2C.  The
PSU's other electrical signals (status, alert, current-share) live
on the CRPS edge connector and are consumed by the chassis
controller rather than the host SoC, so there are no host-described
supplies, GPIOs, clocks, or interrupts.  Add the compatible to
trivial-devices.yaml rather than carrying a standalone binding file.

Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
 Documentation/devicetree/bindings/trivial-devices.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/trivial-devices.yaml b/Documentation/devicetree/bindings/trivial-devices.yaml
index 23fd4513933a..19c8c7220858 100644
--- a/Documentation/devicetree/bindings/trivial-devices.yaml
+++ b/Documentation/devicetree/bindings/trivial-devices.yaml
@@ -352,6 +352,8 @@ properties:
           - mps,mp9941
             # Monolithic Power Systems Inc. digital step-down converter mp9945
           - mps,mp9945
+            # Murata D1U74T-W power supply unit
+          - murata,d1u74t
             # Temperature sensor with integrated fan control
           - national,lm63
             # Temperature sensor with integrated fan control

-- 
2.53.0

Re: [PATCH v4 1/2] dt-bindings: trivial-devices: Add Murata D1U74T PSU

[Krzysztof Kozlowski]

On Thu, May 14, 2026 at 08:03:25PM -0700, Abdurrahman Hussain wrote:
> The Murata D1U74T-W series are hot-pluggable 1U AC/DC front-end
> power supplies in the Intel CRPS-185 / OCP M-CRPS form factor.
> Each variant delivers a 12 V main output plus a 12 V standby output
> from a wide AC input (90-264 Vac) or HVDC supply, and includes an
> internal variable-speed cooling fan and on-board voltage, current,
> power, fan-speed, and temperature telemetry.
> 
> The host-side digital interface is a PMBus 1.2 port on I2C.  The
> PSU's other electrical signals (status, alert, current-share) live
> on the CRPS edge connector and are consumed by the chassis
> controller rather than the host SoC, so there are no host-described
> supplies, GPIOs, clocks, or interrupts.  Add the compatible to
> trivial-devices.yaml rather than carrying a standalone binding file.
> 
> Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof

[PATCH v4 2/2] hwmon: (pmbus/d1u74t) Add Murata D1U74T PSU driver

[Abdurrahman Hussain]

Add PMBUS driver for Murata D1U74T power supplies.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202605122253.zInzmUeX-lkp@intel.com/
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
 Documentation/hwmon/d1u74t.rst | 81 +++++++++++++++++++++++++++++++++++++++
 Documentation/hwmon/index.rst  |  1 +
 MAINTAINERS                    |  7 ++++
 drivers/hwmon/pmbus/Kconfig    |  9 +++++
 drivers/hwmon/pmbus/Makefile   |  1 +
 drivers/hwmon/pmbus/d1u74t.c   | 86 ++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 185 insertions(+)

diff --git a/Documentation/hwmon/d1u74t.rst b/Documentation/hwmon/d1u74t.rst
new file mode 100644
index 000000000000..3a9eedbda483
--- /dev/null
+++ b/Documentation/hwmon/d1u74t.rst
@@ -0,0 +1,81 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver d1u74t
+====================
+
+Supported chips:
+
+  * Murata D1U74T
+
+    Prefix: 'd1u74t'
+
+    Addresses scanned: -
+
+    Datasheet: Publicly available at the Murata website
+
+Authors:
+    Abdurrahman Hussain <abdurrahman@nexthop.ai>
+
+
+Description
+-----------
+
+This driver implements support for Murata D1U74T Power Supply with
+PMBus support.
+
+The driver is a client driver to the core PMBus driver.
+Please see Documentation/hwmon/pmbus.rst for details on PMBus client drivers.
+
+
+Usage Notes
+-----------
+
+This driver does not auto-detect devices. You will have to instantiate the
+devices explicitly. Please see Documentation/i2c/instantiating-devices.rst for
+details.
+
+
+Sysfs entries
+-------------
+
+======================= ======================================================
+curr1_label		"iin"
+curr1_input		Measured input current
+curr1_alarm		Input current alarm
+curr1_rated_max		Maximum rated input current
+
+curr2_label		"iout1"
+curr2_input		Measured output current
+curr2_max		Maximum output current
+curr2_max_alarm		Output current high alarm
+curr2_crit		Critical high output current
+curr2_crit_alarm	Output current critical high alarm
+curr2_rated_max		Maximum rated output current
+
+in1_label		"vin"
+in1_input		Measured input voltage
+in1_alarm		Input voltage alarm
+in1_rated_min		Minimum rated input voltage
+in1_rated_max		Maximum rated input voltage
+
+in2_label		"vout1"
+in2_input		Measured output voltage
+in2_alarm		Output voltage alarm
+in2_rated_min		Minimum rated output voltage
+in2_rated_max		Maximum rated output voltage
+
+power1_label		"pin"
+power1_input		Measured input power
+power1_alarm		Input power alarm
+power1_rated_max	Maximum rated input power
+
+temp[1-3]_input		Measured temperature
+temp[1-3]_max		Maximum temperature
+temp[1-3]_max_alarm	Maximum temperature alarm
+temp[1-3]_rated_max	Maximum rated temperature
+
+fan1_alarm		Fan 1 warning
+fan1_fault		Fan 1 fault
+fan1_input		Fan 1 speed in RPM
+fan1_target		Fan 1 target
+======================= ======================================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 8b655e5d6b68..97b1ef65b1c1 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -60,6 +60,7 @@ Hardware Monitoring Kernel Drivers
    corsair-psu
    cros_ec_hwmon
    crps
+   d1u74t
    da9052
    da9055
    dell-smm-hwmon
diff --git a/MAINTAINERS b/MAINTAINERS
index b2040011a386..3106cf725dfc 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18249,6 +18249,13 @@ F:	drivers/mux/
 F:	include/dt-bindings/mux/
 F:	include/linux/mux/
 
+MURATA D1U74T PSU DRIVER
+M:	Abdurrahman Hussain <abdurrahman@nexthop.ai>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	Documentation/hwmon/d1u74t.rst
+F:	drivers/hwmon/pmbus/d1u74t.c
+
 MUSB MULTIPOINT HIGH SPEED DUAL-ROLE CONTROLLER
 M:	Bin Liu <b-liu@ti.com>
 L:	linux-usb@vger.kernel.org
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 8f4bff375ecb..ee93b22d2887 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -113,6 +113,15 @@ config SENSORS_CRPS
 	  This driver can also be built as a module. If so, the module will
 	  be called crps.
 
+config SENSORS_D1U74T
+	tristate "Murata D1U74T Power Supply"
+	help
+	  If you say yes here you get hardware monitoring support for the Murata
+	  D1U74T Power Supply.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called d1u74t.
+
 config SENSORS_DELTA_AHE50DC_FAN
 	tristate "Delta AHE-50DC fan control module"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 7129b62bc00f..8cf7d3075371 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -76,3 +76,4 @@ obj-$(CONFIG_SENSORS_XDPE1A2G7B)	+= xdpe1a2g7b.o
 obj-$(CONFIG_SENSORS_ZL6100)	+= zl6100.o
 obj-$(CONFIG_SENSORS_PIM4328)	+= pim4328.o
 obj-$(CONFIG_SENSORS_CRPS)	+= crps.o
+obj-$(CONFIG_SENSORS_D1U74T)	+= d1u74t.o
diff --git a/drivers/hwmon/pmbus/d1u74t.c b/drivers/hwmon/pmbus/d1u74t.c
new file mode 100644
index 000000000000..286ba492e336
--- /dev/null
+++ b/drivers/hwmon/pmbus/d1u74t.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2026 Nexthop Systems.
+ */
+
+#include <linux/i2c.h>
+#include <linux/of.h>
+#include <linux/pmbus.h>
+
+#include "pmbus.h"
+
+static const struct i2c_device_id d1u74t_id[] = {
+	{ "d1u74t" },
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, d1u74t_id);
+
+static struct pmbus_driver_info d1u74t_info = {
+	.pages = 1,
+	/* PSU uses default linear data format. */
+	.func[0] = PMBUS_HAVE_PIN | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		   PMBUS_HAVE_IIN | PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT |
+		   PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT | PMBUS_HAVE_TEMP |
+		   PMBUS_HAVE_TEMP2 | PMBUS_HAVE_TEMP3 |
+		   PMBUS_HAVE_STATUS_TEMP | PMBUS_HAVE_FAN12 |
+		   PMBUS_HAVE_STATUS_FAN12,
+};
+
+static int d1u74t_probe(struct i2c_client *client)
+{
+	char buf[I2C_SMBUS_BLOCK_MAX + 2] = { 0 };
+	struct device *dev = &client->dev;
+	int rc;
+
+	rc = i2c_smbus_read_block_data(client, PMBUS_MFR_ID, buf);
+	if (rc < 0)
+		return dev_err_probe(dev, rc, "Failed to read PMBUS_MFR_ID\n");
+
+	if (rc != 9 || strncmp(buf, "Murata-PS", 9)) {
+		buf[rc] = '\0';
+		return dev_err_probe(dev, -ENODEV,
+				     "Unsupported Manufacturer ID '%s'\n",
+				     buf);
+	}
+
+	rc = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
+	if (rc < 0)
+		return dev_err_probe(dev, rc,
+				     "Failed to read PMBUS_MFR_MODEL\n");
+
+	if (rc < 8 || strncmp(buf, "D1U74T-W", 8)) {
+		buf[rc] = '\0';
+		return dev_err_probe(dev, -ENODEV, "Model '%s' not supported\n",
+				     buf);
+	}
+
+	rc = pmbus_do_probe(client, &d1u74t_info);
+	if (rc)
+		return dev_err_probe(dev, rc, "Failed to probe\n");
+
+	return 0;
+}
+
+static const struct of_device_id d1u74t_of_match[] = {
+	{
+		.compatible = "murata,d1u74t",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, d1u74t_of_match);
+
+static struct i2c_driver d1u74t_driver = {
+	.driver = {
+		.name = "d1u74t",
+		.of_match_table = d1u74t_of_match,
+	},
+	.probe = d1u74t_probe,
+	.id_table = d1u74t_id,
+};
+
+module_i2c_driver(d1u74t_driver);
+
+MODULE_AUTHOR("Abdurrahman Hussain");
+MODULE_DESCRIPTION("PMBus driver for Murata D1U74T-W power supplies");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("PMBUS");

-- 
2.53.0

Re: [PATCH v4 2/2] hwmon: (pmbus/d1u74t) Add Murata D1U74T PSU driver

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] Missing includes for <linux/module.h> and <linux/string.h>.
- [Low] Logging raw I2C device strings without escaping.
--

commit f645f72f2f4d8cc53bec169fb4350e6231e649a4
Author: Abdurrahman Hussain <abdurrahman@nexthop.ai>

hwmon: (pmbus/d1u74t) Add Murata D1U74T PSU driver

This commit adds a PMBus client driver for the Murata D1U74T power supplies.

Closes: https://lore.kernel.org/oe-kbuild-all/202605122253.zInzmUeX-lkp@intel.com/

> diff --git a/drivers/hwmon/pmbus/d1u74t.c b/drivers/hwmon/pmbus/d1u74t.c
> new file mode 100644
> index 0000000000000..286ba492e3362
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/d1u74t.c
> @@ -0,0 +1,86 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright 2026 Nexthop Systems.
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/of.h>
> +#include <linux/pmbus.h>
> +
> +#include "pmbus.h"

This isn't a bug, but should this file include <linux/module.h> and
<linux/string.h>? It uses module-specific macros like MODULE_DEVICE_TABLE
and MODULE_AUTHOR, as well as the strncmp function. While compilation might
succeed due to transitive includes, it could lead to build failures or
implicit declaration warnings on some architectures.

[ ... ]

> +static int d1u74t_probe(struct i2c_client *client)
> +{
> +	char buf[I2C_SMBUS_BLOCK_MAX + 2] = { 0 };
> +	struct device *dev = &client->dev;
> +	int rc;
> +
> +	rc = i2c_smbus_read_block_data(client, PMBUS_MFR_ID, buf);
> +	if (rc < 0)
> +		return dev_err_probe(dev, rc, "Failed to read PMBUS_MFR_ID\n");
> +
> +	if (rc != 9 || strncmp(buf, "Murata-PS", 9)) {
> +		buf[rc] = '\0';
> +		return dev_err_probe(dev, -ENODEV,
> +				     "Unsupported Manufacturer ID '%s'\n",
> +				     buf);
> +	}
> +
> +	rc = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
> +	if (rc < 0)
> +		return dev_err_probe(dev, rc,
> +				     "Failed to read PMBUS_MFR_MODEL\n");
> +
> +	if (rc < 8 || strncmp(buf, "D1U74T-W", 8)) {
> +		buf[rc] = '\0';
> +		return dev_err_probe(dev, -ENODEV, "Model '%s' not supported\n",
> +				     buf);
> +	}

Does this code log potentially unescaped strings directly from the device?

Since the I2C bus can return garbage data or unprintable characters from a
malfunctioning device, using the %s format specifier could result in
corrupted log output. Would it be safer to use the %*pE specifier to safely
escape these untrusted strings?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260514-d1u74t-v4-0-1f1ee7b002ec@nexthop.ai?part=2