samples: rust: platform: Add property read examples

Add some example usage of the device property read methods for
DT/ACPI/swnode properties.

Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Co-developed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Remo Senekowitsch <remo@buenzli.dev>

Author: senekor

drivers/of/unittest-data/tests-platform.dtsi

@@ -37,6 +37,9 @@
 			test-device@2 {
 				compatible = "test,rust-device";
 				reg = <0x2>;
+
+				test,u32-prop = <0xdeadbeef>;
+				test,i16-array = /bits/ 16 <1 2 (-3) (-4)>;
 			};
 		};
 

samples/rust/rust_driver_platform.rs

@@ -2,7 +2,14 @@
 
 //! Rust Platform driver sample.
 
-use kernel::{c_str, device::Core, of, platform, prelude::*, types::ARef};
+use kernel::{
+    c_str,
+    device::{self, Core},
+    of, platform,
+    prelude::*,
+    str::CString,
+    types::ARef,
+};
 
 struct SampleDriver {
     pdev: ARef<platform::Device>,
@@ -31,12 +38,63 @@ impl platform::Driver for SampleDriver {
             dev_info!(pdev.as_ref(), "Probed with info: '{}'.\n", info.0);
         }
 
+        Self::properties_parse(pdev.as_ref())?;
+
         let drvdata = KBox::new(Self { pdev: pdev.into() }, GFP_KERNEL)?;
 
         Ok(drvdata.into())
     }
 }
 
+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_str!("compatible"), c_str!("test,rust-device"))
+        {
+            dev_info!(dev, "matched compatible string idx = {}\n", idx);
+        }
+
+        let name = c_str!("compatible");
+        let prop = fwnode.property_read::<CString>(name).required_by(dev)?;
+        dev_info!(dev, "'{name}'='{prop:?}'\n");
+
+        let name = c_str!("test,bool-prop");
+        let prop = fwnode.property_read_bool(c_str!("test,bool-prop"));
+        dev_info!(dev, "'{name}'='{prop}'\n");
+
+        if fwnode.property_present(c_str!("test,u32-prop")) {
+            dev_info!(dev, "'test,u32-prop' is present\n");
+        }
+
+        let name = c_str!("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_str!("test,u32-required-prop");
+        let _ = fwnode.property_read::<u32>(name).required_by(dev);
+
+        let name = c_str!("test,u32-prop");
+        let prop: u32 = fwnode.property_read(name).required_by(dev)?;
+        dev_info!(dev, "'{name}'='{prop:#x}'\n");
+
+        let name = c_str!("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_str!("test,i16-array");
+        let prop: KVec<i16> = fwnode.property_read_array_vec(name, 4)?.required_by(dev)?;
+        dev_info!(dev, "'{name}'='{prop:?}' (KVec)\n");
+
+        Ok(())
+    }
+}
+
 impl Drop for SampleDriver {
     fn drop(&mut self) {
         dev_dbg!(self.pdev.as_ref(), "Remove Rust Platform driver sample.\n");