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

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Message-ID: <20250326220129.GD2844851-robh@kernel.org>
Date: Wed, 26 Mar 2025 17:01:29 -0500
From: Rob Herring <robh@...nel.org>
To: Remo Senekowitsch <remo@...nzli.dev>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Daniel Scally <djrscally@...il.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Dirk Behme <dirk.behme@...bosch.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...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>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	devicetree@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 10/10] samples: rust: platform: Add property read examples

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@...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         | 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
>