[PATCH RFC 3/4] samples: rust: add Rust serial device bus sample device driver

[Markus Probst <markus.probst@posteo.de>]

Add a sample Rust serial device bus device driver illustrating the usage
of the platform bus abstractions.

This drivers probes through either a match of device / driver name or a
match within the OF ID table.
---
 samples/rust/Kconfig               |  10 +++
 samples/rust/Makefile              |   1 +
 samples/rust/rust_driver_serdev.rs | 175 +++++++++++++++++++++++++++++++++++++
 3 files changed, 186 insertions(+)

diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index 3efa51bfc8ef..3b6663b4bc9b 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -161,6 +161,16 @@ config SAMPLE_RUST_DRIVER_AUXILIARY
 
 	  If unsure, say N.
 
+config SAMPLE_RUST_DRIVER_SERDEV
+	tristate "Serial Device Bus Device Driver"
+	help
+	  This option builds the Rust serial device bus driver sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_driver_serdev.
+
+	  If unsure, say N.
+
 config SAMPLE_RUST_HOSTPROGS
 	bool "Host programs"
 	help
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index f65885d1d62b..ec5cb8065fb7 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM)	+= rust_driver_platform.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_USB)		+= rust_driver_usb.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_FAUX)		+= rust_driver_faux.o
 obj-$(CONFIG_SAMPLE_RUST_DRIVER_AUXILIARY)	+= rust_driver_auxiliary.o
+obj-$(CONFIG_SAMPLE_RUST_DRIVER_SERDEV)		+= rust_driver_serdev.o
 obj-$(CONFIG_SAMPLE_RUST_CONFIGFS)		+= rust_configfs.o
 
 rust_print-y := rust_print_main.o rust_print_events.o
diff --git a/samples/rust/rust_driver_serdev.rs b/samples/rust/rust_driver_serdev.rs
new file mode 100644
index 000000000000..f23b38a26c32
--- /dev/null
+++ b/samples/rust/rust_driver_serdev.rs
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust Serial device bus device driver sample.
+
+use kernel::{
+    acpi,
+    device::{
+        self,
+        property::{
+            FwNodeReferenceArgs,
+            NArgs, //
+        },
+        Bound,
+        Core, //
+    },
+    of,
+    prelude::*,
+    serdev,
+    str::CString,
+    sync::aref::ARef, //
+};
+
+struct SampleDriver {
+    sdev: ARef<serdev::Device>,
+}
+
+struct Info(u32);
+
+kernel::of_device_table!(
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <SampleDriver as serdev::Driver>::IdInfo,
+    [(of::DeviceId::new(c"test,rust_driver_serdev"), Info(42))]
+);
+
+kernel::acpi_device_table!(
+    ACPI_TABLE,
+    MODULE_ACPI_TABLE,
+    <SampleDriver as serdev::Driver>::IdInfo,
+    [(acpi::DeviceId::new(c"LNUXBEEF"), Info(0))]
+);
+
+#[vtable]
+impl serdev::Driver for SampleDriver {
+    type IdInfo = Info;
+    type InitialData = ();
+    type LateProbeData = ();
+    const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+    const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = Some(&ACPI_TABLE);
+
+    fn probe(sdev: &serdev::Device, info: Option<&Self::IdInfo>) -> impl PinInit<Self, Error> {
+        let dev = sdev.as_ref();
+
+        dev_dbg!(dev, "Probe Rust Serial device bus device driver sample.\n");
+
+        if let Some(info) = info {
+            dev_info!(dev, "Probed with info: '{}'.\n", info.0);
+        }
+
+        if dev.fwnode().is_some_and(|node| node.is_of_node()) {
+            Self::properties_parse(dev)?;
+        }
+
+        Ok(Self { sdev: sdev.into() })
+    }
+
+    fn configure(
+        sdev: &serdev::Device<Core>,
+        _this: Pin<&Self>,
+        _id_info: Option<&Self::IdInfo>,
+    ) -> Result {
+        dev_dbg!(
+            sdev.as_ref(),
+            "Configure Rust Serial device bus device driver sample.\n"
+        );
+
+        sdev.set_baudrate(115200);
+        sdev.set_flow_control(false);
+        sdev.set_parity(serdev::Parity::None)?;
+        Ok(())
+    }
+
+    fn late_probe(
+        sdev: &serdev::Device<Bound>,
+        _this: Pin<&Self>,
+        _initial_data: Self::InitialData,
+    ) -> impl PinInit<Self::LateProbeData, Error> {
+        dev_dbg!(
+            sdev.as_ref(),
+            "Late Probe Rust Serial device bus device driver sample.\n"
+        );
+        Ok(())
+    }
+
+    fn receive(
+        sdev: &serdev::Device<Bound>,
+        _this: Pin<&Self>,
+        _late_probe_this: Pin<&Self::LateProbeData>,
+        data: &[u8],
+    ) -> usize {
+        let _ = sdev.write_all(data, serdev::Timeout::MaxScheduleTimeout);
+        data.len()
+    }
+}
+
+impl SampleDriver {
+    fn properties_parse(dev: &device::Device) -> Result {
+        let fwnode = dev.fwnode().ok_or(ENOENT)?;
+
+        if let Ok(idx) = fwnode.property_match_string(c"compatible", c"test,rust-device") {
+            dev_info!(dev, "matched compatible string idx = {}\n", idx);
+        }
+
+        let name = c"compatible";
+        let prop = fwnode.property_read::<CString>(name).required_by(dev)?;
+        dev_info!(dev, "'{name}'='{prop:?}'\n");
+
+        let name = c"test,bool-prop";
+        let prop = fwnode.property_read_bool(c"test,bool-prop");
+        dev_info!(dev, "'{name}'='{prop}'\n");
+
+        if fwnode.property_present(c"test,u32-prop") {
+            dev_info!(dev, "'test,u32-prop' is present\n");
+        }
+
+        let name = c"test,u32-optional-prop";
+        let prop = fwnode.property_read::<u32>(name).or(0x12);
+        dev_info!(dev, "'{name}'='{prop:#x}' (default = 0x12)\n");
+
+        // A missing required property will print an error. Discard the error to
+        // prevent properties_parse from failing in that case.
+        let name = c"test,u32-required-prop";
+        let _ = fwnode.property_read::<u32>(name).required_by(dev);
+
+        let name = c"test,u32-prop";
+        let prop: u32 = fwnode.property_read(name).required_by(dev)?;
+        dev_info!(dev, "'{name}'='{prop:#x}'\n");
+
+        let name = c"test,i16-array";
+        let prop: [i16; 4] = fwnode.property_read(name).required_by(dev)?;
+        dev_info!(dev, "'{name}'='{prop:?}'\n");
+        let len = fwnode.property_count_elem::<u16>(name)?;
+        dev_info!(dev, "'{name}' length is {len}\n");
+
+        let name = c"test,i16-array";
+        let prop: KVec<i16> = fwnode.property_read_array_vec(name, 4)?.required_by(dev)?;
+        dev_info!(dev, "'{name}'='{prop:?}' (KVec)\n");
+
+        for child in fwnode.children() {
+            let name = c"test,ref-arg";
+            let nargs = NArgs::N(2);
+            let prop: FwNodeReferenceArgs = child.property_get_reference_args(name, nargs, 0)?;
+            dev_info!(dev, "'{name}'='{prop:?}'\n");
+        }
+
+        Ok(())
+    }
+}
+
+impl Drop for SampleDriver {
+    fn drop(&mut self) {
+        dev_dbg!(
+            self.sdev.as_ref(),
+            "Remove Rust Serial device bus device driver sample.\n"
+        );
+    }
+}
+
+kernel::module_serdev_device_driver! {
+    type: SampleDriver,
+    name: "rust_driver_serdev",
+    authors: ["Markus Probst"],
+    description: "Rust Serial device bus device driver",
+    license: "GPL v2",
+}

-- 
2.51.2