linux-kernel - [PATCH v3 7/7] samples: rust: platform: Add property read examples

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Message-ID: <20250425150130.13917-8-remo@buenzli.dev>
Date: Fri, 25 Apr 2025 17:01:30 +0200
From: Remo Senekowitsch <remo@...nzli.dev>
To: Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Dirk Behme <dirk.behme@...bosch.com>,
	Remo Senekowitsch <remo@...nzli.dev>
Cc: linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Subject: [PATCH v3 7/7] samples: rust: platform: Add property read examples

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

Co-developed-by: Rob Herring (Arm) <robh@...nel.org>
Signed-off-by: Rob Herring (Arm) <robh@...nel.org>
Signed-off-by: Remo Senekowitsch <remo@...nzli.dev>
---
 drivers/of/unittest-data/tests-platform.dtsi |  3 +
 samples/rust/rust_driver_platform.rs         | 72 +++++++++++++++++++-
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/drivers/of/unittest-data/tests-platform.dtsi b/drivers/of/unittest-data/tests-platform.dtsi
index 4171f43cf..50a51f38a 100644
--- a/drivers/of/unittest-data/tests-platform.dtsi
+++ b/drivers/of/unittest-data/tests-platform.dtsi
@@ -37,6 +37,9 @@ dev@100 {
 			test-device@2 {
 				compatible = "test,rust-device";
 				reg = <0x2>;
+
+				test,u32-prop = <0xdeadbeef>;
+				test,i16-array = /bits/ 16 <1 2 (-3) (-4)>;
 			};
 		};
 
diff --git a/samples/rust/rust_driver_platform.rs b/samples/rust/rust_driver_platform.rs
index 8120609e2..04731baa7 100644
--- a/samples/rust/rust_driver_platform.rs
+++ b/samples/rust/rust_driver_platform.rs
@@ -2,7 +2,7 @@
 
 //! Rust Platform driver sample.
 
-use kernel::{c_str, of, platform, prelude::*};
+use kernel::{c_str, of, platform, prelude::*, str::CString};
 
 struct SampleDriver {
     pdev: platform::Device,
@@ -22,18 +22,84 @@ impl platform::Driver for SampleDriver {
     const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
 
     fn probe(pdev: &mut platform::Device, info: Option<&Self::IdInfo>) -> Result<Pin<KBox<Self>>> {
-        dev_dbg!(pdev.as_ref(), "Probe Rust Platform driver sample.\n");
+        let dev = pdev.as_ref();
+
+        dev_dbg!(dev, "Probe Rust Platform driver sample.\n");
 
         if let Some(info) = info {
-            dev_info!(pdev.as_ref(), "Probed with info: '{}'.\n", info.0);
+            dev_info!(dev, "Probed with info: '{}'.\n", info.0);
         }
 
+        Self::properties_parse(dev)?;
+
         let drvdata = KBox::new(Self { pdev: pdev.clone() }, GFP_KERNEL)?;
 
         Ok(drvdata.into())
     }
 }
 
+impl SampleDriver {
+    fn properties_parse(dev: &kernel::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);
+        }
+
+        if let Ok(str) = fwnode
+            .property_read::<CString>(c_str!("compatible"))
+            .required()
+        {
+            dev_info!(dev, "compatible string = {:?}\n", str);
+        }
+
+        let prop = fwnode.property_read_bool(c_str!("test,bool-prop"));
+        dev_info!(dev, "bool prop is {}\n", prop);
+
+        if fwnode.property_present(c_str!("test,u32-prop")) {
+            dev_info!(dev, "'test,u32-prop' is present\n");
+        }
+
+        let prop = fwnode
+            .property_read::<u32>(c_str!("test,u32-optional-prop"))
+            .or(0x12);
+        dev_info!(
+            dev,
+            "'test,u32-optional-prop' is {:#x} (default = {:#x})\n",
+            prop,
+            0x12
+        );
+
+        // Missing property without a default will print an error
+        let _ = fwnode
+            .property_read::<u32>(c_str!("test,u32-required-prop"))
+            .required();
+
+        let prop: u32 = fwnode.property_read(c_str!("test,u32-prop")).required()?;
+        dev_info!(dev, "'test,u32-prop' is {:#x}\n", prop);
+
+        // TODO: remove or replace with u16? `Property` is not implemented for
+        // unsigned integers, as suggested by Andy Shevchenko.
+
+        let prop: [i16; 4] = fwnode.property_read(c_str!("test,i16-array")).required()?;
+        dev_info!(dev, "'test,i16-array' is {:?}\n", prop);
+        dev_info!(
+            dev,
+            "'test,i16-array' length is {}\n",
+            fwnode.property_count_elem::<u16>(c_str!("test,i16-array"))?,
+        );
+
+        let prop: KVec<i16> = fwnode
+            .property_read_array_vec(c_str!("test,i16-array"), 4)?
+            .required()?;
+        dev_info!(dev, "'test,i16-array' is KVec {:?}\n", prop);
+
+        Ok(())
+    }
+}
+
 impl Drop for SampleDriver {
     fn drop(&mut self) {
         dev_dbg!(self.pdev.as_ref(), "Remove Rust Platform driver sample.\n");
-- 
2.49.0