Re: [PATCH v2 5/5] samples: rust: platform: Add property read examples

[Dirk Behme <dirk.behme@de.bosch.com>]

Hi Remo,

On 14/04/2025 17:26, 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         | 69 +++++++++++++++++++-
>  2 files changed, 69 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)>;


Is "test,u32-required-prop" missing here? See below ...


>  			};
>  		};
>  
> diff --git a/samples/rust/rust_driver_platform.rs b/samples/rust/rust_driver_platform.rs
> index 8120609e2..0284f1840 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 +22,81 @@ 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<()> {
> +        if let Ok(idx) = dev.property_match_string(c_str!("compatible"), c_str!("test,rust-device"))
> +        {
> +            dev_info!(dev, "matched compatible string idx = {}\n", idx);
> +        }
> +
> +        if let Ok(str) = dev
> +            .property_read::<CString>(c_str!("compatible"))
> +            .required()
> +        {
> +            dev_info!(dev, "compatible string = {:?}\n", str);
> +        }
> +
> +        let prop = dev.property_read_bool(c_str!("test,bool-prop"));
> +        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()?;


On x86 using above dtsi it seems it error exits here:

[    2.178227] rust_driver_platform
testcase-data:platform-tests:test-device@2: Probed with info: '42'.


[    2.178715] rust_driver_platform
testcase-data:platform-tests:test-device@2: matched compatible string
idx = 0

[    2.179122] rust_driver_platform
testcase-data:platform-tests:test-device@2: compatible string =
"test,rust-device"

[    2.179563] rust_driver_platform
testcase-data:platform-tests:test-device@2: bool prop is false


[    2.179841] rust_driver_platform
testcase-data:platform-tests:test-device@2: 'test,u32-prop' is present


[    2.180200] rust_driver_platform
testcase-data:platform-tests:test-device@2: 'test,u32-optional-prop' is
0x12 (default = 0x12)

[    2.180598] rust_driver_platform
testcase-data:platform-tests:test-device@2:
/testcase-data/platform-tests/test-device@2: property
'test,u32-required-prop' is missing
[    2.181244] rust_driver_platform
testcase-data:platform-tests:test-device@2: probe with driver
rust_driver_platform failed with error -22

I'm not sure if this is what we want?

Best regards

Dirk


> +        let prop: u32 = dev.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] = 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"))?,
> +        );
> +
> +        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);
> +
> +        Ok(())
> +    }
> +}
> +