mctpd: Support MCTP Discovery Notify command

CHANGELOG.md

@@ -18,6 +18,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
    To support this, the minimum meson version has been bumped to 0.60,
    previously 0.59.
 
+3. `mctpd` now supports autonomous periodic discovery on point-to-point
+   physical links (e.g. Serial, USB, KCS) operating in Bus Owner mode.
+   Background probing automatically discovers and assigns EIDs to endpoints
+   once the interface is brought UP, with support for per-interface probe
+   intervals and static EID reservations.
+
 ### Fixes
 
 1. In v2.6. we lost the peer initial MTU sematics, which gave us a safe minimum

conf/mctpd.conf

@@ -20,3 +20,27 @@ max_pool_size = 15
 # Bus Owner/bridge polling interval (ms) to check endpoint accessibility.
 # A value of 0 disables polling.
 endpoint_poll_ms = 0
+
+# Autonomous periodic discovery for point-to-point addressless interfaces (e.g. Serial, USB, KCS)
+# Default is false.
+auto_discovery = false
+
+# Periodic probing interval (ms) for point-to-point interfaces (100 - 60000 ms)
+probe_interval_ms = 1000
+
+# Interface specific configuration examples:
+#
+# [[interface]]
+# match = { phys-type = "serial" }
+# role = "bus-owner"
+# auto_discovery = true
+# probe_interval_ms = 500
+# static_eid = 8
+#
+# [[interface]]
+# match = { phys-type = "usb" }
+# role = "bus-owner"
+# auto_discovery = true
+# probe_interval_ms = 500
+# static_eid = 9
+

docs/mctpd.md

@@ -434,6 +434,24 @@ Such periodic polling is common for all the briged endpoints among allocated
 pool space [`.PoolStart` - `.PoolEnd`] of the bridge.
 Polling could be provisioned to be disabled via setting the value as ```0```.
 
+#### `auto_discovery`: Autonomous periodic probing on point-to-point links
+
+* type: boolean
+* default: `false`
+
+Enables autonomous background probing (`Get Endpoint ID` 0x02) for addressless
+point-to-point links (e.g. Serial, USB, KCS) running in `bus-owner` mode. When enabled,
+`mctpd` automatically probes the link when brought `IFF_UP` until the endpoint
+responds, assigns an EID, and transitions the link to `DISCOVERY_DISCOVERED`.
+
+#### `probe_interval_ms`: Periodic probing interval for point-to-point links
+
+* type: integer, in milliseconds
+* default: 1000
+
+Specifies the period between probe attempts on point-to-point links. Valid range is
+`100` ms to `60000` ms.
+
 ### `[[interface]]`: per-interface configuration
 
 The `[[interface]]` table allows configuration to be applied to specific
@@ -443,12 +461,34 @@ determines which MCTP interfaces the table applies to.
 Matches are processed in the order they appear in the configuration file;
 the first `[[interface]]` section that matches is applied.
 
-Other content of the interface table is configuration to be applied. The
-only setting currently supported is `role`, to set mctpd's role as
-either bus-owner or endpoint on this interface.
+Supported settings per interface:
+* `role`: sets mctpd's role as either `bus-owner` or `endpoint` on this interface.
+* `auto_discovery`: overrides global `auto_discovery` for this interface (`true`/`false`).
+* `probe_interval_ms`: overrides global probe interval in milliseconds (`100` - `60000`).
+* `static_eid`: assigns a fixed static EID (must be in `[8, dynamic_eid_start)`) upon successful probe response, preventing dynamic EID allocation collisions.
+
+For example, to configure static EIDs and custom probe intervals on point-to-point links:
 
-For example, to apply a `bus-owner` role globally, with interface-specific
-`endpoint` roles for all i2c devices, and one particular (USB) device:
+```toml
+[bus-owner]
+dynamic_eid_range = [16, 64]
+auto_discovery = true
+probe_interval_ms = 1000
+
+[[interface]]
+match = { phys-type = "serial" }
+role = "bus-owner"
+auto_discovery = true
+probe_interval_ms = 500
+static_eid = 8
+
+[[interface]]
+match = { phys-type = "usb" }
+role = "bus-owner"
+auto_discovery = true
+probe_interval_ms = 500
+static_eid = 9
+```
 
 ```toml
 role = "bus-owner"