Re: [PATCH 10/10] samples: rust: platform: Add property read examples

Rob Herring
2025-03-26T22:01:31Z

On Wed, Mar 26, 2025 at 06:13:49PM +0100, Remo Senekowitsch wrote:
> Add some example usage of the device property read methods for
> DT/ACPI/swnode properties.
>
> 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>
> ---
> drivers/of/unittest-data/tests-platform.dtsi | 3 ++
> samples/rust/rust_driver_platform.rs | 56 +++++++++++++++++++-
> 2 files changed, 58 insertions(+), 1 deletion(-)
>
> 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..ed25a3781 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,
> @@ -28,6 +28,60 @@ fn probe(pdev: &mut platform::Device, info: Option<&Self::IdInfo>) -> Result<Pin
> dev_info!(pdev.as_ref(), "Probed with info: '{}'.\n", info.0);
> }
>
> + let dev = pdev.as_ref();

We should move this to the top and replace all the 'pdev.as_ref()' with
'dev'.

> + if let Ok(idx) = dev.property_match_string(c_str!("compatible"), c_str!("test,rust-device"))
> + {
> + dev_info!(pdev.as_ref(), "matched compatible string idx = {}\n", idx);

Like here. (Looks like this is my fault.)

> + }
> +
> + if let Ok(str) = dev
> + .property_read::<CString>(c_str!("compatible"))
> + .required()
> + {
> + dev_info!(pdev.as_ref(), "compatible string = {:?}\n", str);
> + }
> +
> + let prop = dev
> + .property_read::<bool>(c_str!("test,bool-prop"))
> + .required()?;

The 'required' is kind of odd for boolean properties. They are never
required as not present is the only way to to get false.

> + dev_info!(dev, "bool prop is {}\n", prop);
> +
> + if dev.property_present(c_str!("test,u32-prop")) {
> + dev_info!(dev, "'test,u32-prop' is present\n");
> + }
> +
> + let prop = dev
> + .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 _ = dev
> + .property_read::<u32>(c_str!("test,u32-required-prop"))
> + .required()?;
> +
> + let prop: u32 = dev.property_read(c_str!("test,u32-prop")).required()?;
> + dev_info!(dev, "'test,u32-prop' is {:#x}\n", prop);
> +
> + let prop: [i16; 4] = dev.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",
> + dev.property_count_elem::<u16>(c_str!("test,i16-array"))
> + .unwrap()
> + );
> +
> + let prop: KVec<i16> = dev
> + .property_read_array_vec(c_str!("test,i16-array"), 4)?
> + .required()?;
> + dev_info!(dev, "'test,i16-array' is KVec {:?}\n", prop);
> +
> let drvdata = KBox::new(Self { pdev: pdev.clone() }, GFP_KERNEL)?;
>
> Ok(drvdata.into())
> --
> 2.49.0
>