diff --git a/Cargo.lock b/Cargo.lock
index 19b984cebb..ece9f7bd9e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3146,7 +3146,7 @@ checksum = "e6d5a32815ae3f33302d95fdcb2ce17862f8c65363dcfd29360480ba1001fc9c"
 [[package]]
 name = "gateway-ereport-messages"
 version = "0.1.0"
-source = "git+https://github.com/oxidecomputer/management-gateway-service#177c9c719e12896c566a1b6b5416c9bc686531d3"
+source = "git+https://github.com/oxidecomputer/management-gateway-service#745a508cb97b7ca9b4c10ec9592c980eb769b10d"
 dependencies = [
  "zerocopy 0.8.27",
 ]
@@ -3154,7 +3154,7 @@ dependencies = [
 [[package]]
 name = "gateway-messages"
 version = "0.1.0"
-source = "git+https://github.com/oxidecomputer/management-gateway-service#177c9c719e12896c566a1b6b5416c9bc686531d3"
+source = "git+https://github.com/oxidecomputer/management-gateway-service#745a508cb97b7ca9b4c10ec9592c980eb769b10d"
 dependencies = [
  "bitflags 2.9.4",
  "hubpack",
diff --git a/build/i2c/src/lib.rs b/build/i2c/src/lib.rs
index 6774116bd7..4305f8ccf2 100644
--- a/build/i2c/src/lib.rs
+++ b/build/i2c/src/lib.rs
@@ -1782,6 +1782,27 @@ pub struct I2cDeviceDescription {
     pub sensors: Vec<DeviceSensor>,
     pub device_id: Option<String>,
     pub name: Option<String>,
+    /// If this is a PMBus device, this field contains additional data about the
+    /// PMBus device to be used for generating PMBus-y code.
+    pub pmbus: Option<PmbusDeviceDescription>,
+}
+
+#[derive(Debug, Clone)]
+pub struct PmbusDeviceDescription {
+    pub rails: Vec<PmbusRailDescription>,
+}
+
+#[derive(Debug, Clone)]
+pub struct PmbusRailDescription {
+    pub name: String,
+    pub phases: Vec<u8>,
+}
+
+impl I2cDeviceDescription {
+    /// Returns `true` if this device is a PMBus device.
+    pub fn is_pmbus(&self) -> bool {
+        self.pmbus.is_some()
+    }
 }
 
 ///
@@ -1801,12 +1822,59 @@ pub fn device_descriptions() -> impl Iterator<Item = I2cDeviceDescription> {
     g.devices.into_iter().zip(sensors.device_sensors).map(
         |(device, sensors)| {
             let device_id = device.refdes.as_ref().map(Refdes::to_component_id);
+            let pmbus = device.power.as_ref().and_then(|power| {
+                if !power.pmbus {
+                    return None;
+                }
+
+                let rails = match (power.rails.as_ref(), power.phases.as_ref())
+                {
+                    (Some(rails), Some(phases)) => {
+                        assert_eq!(
+                            rails.len(),
+                            phases.len(),
+                            "invalid config: PMBus device {device_id:?}'s \
+                             `power.rails` and  `power.phases` lists are not \
+                             the same length"
+                        );
+                        rails
+                            .iter()
+                            .cloned()
+                            .zip(phases.iter().cloned())
+                            .map(|(name, phases)| PmbusRailDescription {
+                                name,
+                                phases,
+                            })
+                            .collect()
+                    }
+                    (Some(rails), None) => rails
+                        .iter()
+                        .cloned()
+                        .map(|name| PmbusRailDescription {
+                            name,
+                            phases: Vec::new(),
+                        })
+                        .collect(),
+                    (None, Some(_)) => {
+                        panic!(
+                            "invalid config: PMBus device {device_id:?} \
+                            defines a `power.phases` list, but not a \
+                            `power.rails` list"
+                        );
+                    }
+                    (None, None) => Vec::new(),
+                };
+
+                Some(PmbusDeviceDescription { rails })
+            });
+
             I2cDeviceDescription {
                 device: device.device,
                 description: device.description,
                 sensors,
                 device_id,
                 name: device.name,
+                pmbus,
             }
         },
     )
diff --git a/task/control-plane-agent/src/inventory.rs b/task/control-plane-agent/src/inventory.rs
index f9bead6fa2..1ccc860bda 100644
--- a/task/control-plane-agent/src/inventory.rs
+++ b/task/control-plane-agent/src/inventory.rs
@@ -123,6 +123,9 @@ impl Inventory {
         };
 
         let mut capabilities = DeviceCapabilities::empty();
+        if device.is_pmbus {
+            capabilities |= DeviceCapabilities::IS_PMBUS;
+        }
         if !device.sensors.is_empty() {
             capabilities |= DeviceCapabilities::HAS_MEASUREMENT_CHANNELS;
         }
diff --git a/task/validate-api/build.rs b/task/validate-api/build.rs
index 869ef1c4dc..4f0d3c8b40 100644
--- a/task/validate-api/build.rs
+++ b/task/validate-api/build.rs
@@ -59,12 +59,13 @@ fn write_pub_device_descriptions() -> anyhow::Result<()> {
     let mut id2idx = std::collections::BTreeMap::new();
 
     for (idx, dev) in devices.into_iter().enumerate() {
+        let is_pmbus = dev.is_pmbus();
         writeln!(file, "    DeviceDescription {{")?;
         writeln!(file, "        device: {:?},", dev.device)?;
         writeln!(file, "        description: {:?},", dev.description)?;
         if let Some(id) = dev.device_id {
             if let Ok(component) = SpComponent::try_from(id.as_ref()) {
-                write!(file, "        id: {:?},", component.id)?;
+                writeln!(file, "        id: {:?},", component.id)?;
                 if id2idx.insert(component.id, idx).is_some() {
                     println!("cargo::error=duplicate device id {id:?}",);
                     duplicate_ids += 1;
@@ -83,6 +84,7 @@ fn write_pub_device_descriptions() -> anyhow::Result<()> {
             );
             missing_ids += 1;
         };
+        writeln!(file, "        is_pmbus: {is_pmbus:?},")?;
         writeln!(file, "        sensors: &[")?;
         for s in dev.sensors {
             writeln!(file, "            SensorDescription {{")?;
diff --git a/task/validate-api/src/lib.rs b/task/validate-api/src/lib.rs
index 3884406f07..b55d93cd14 100644
--- a/task/validate-api/src/lib.rs
+++ b/task/validate-api/src/lib.rs
@@ -75,6 +75,7 @@ pub struct DeviceDescription {
     pub description: &'static str,
     pub sensors: &'static [SensorDescription],
     pub id: [u8; MAX_ID_LENGTH],
+    pub is_pmbus: bool,
 }
 
 include!(concat!(env!("OUT_DIR"), "/device_descriptions.rs"));