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

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
---
 drivers/of/unittest-data/tests-platform.dtsi |  3 +++
 samples/rust/rust_driver_platform.rs         | 22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/drivers/of/unittest-data/tests-platform.dtsi b/drivers/of/unittest-data/tests-platform.dtsi
index 2caaf1c10ee6..a5369b9343b8 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 5cf4a8f86c13..95c290806862 100644
--- a/samples/rust/rust_driver_platform.rs
+++ b/samples/rust/rust_driver_platform.rs
@@ -41,6 +41,28 @@ fn probe(pdev: &mut platform::Device, info: Option<&Self::IdInfo>) -> Result<Pin
             }
         };
 
+        let dev = pdev.as_ref();
+        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);
+        }
+
+        let prop = dev.property_read_bool(c_str!("test,bool-prop"));
+        dev_info!(dev, "bool prop is {}\n", prop);
+
+        let _prop = dev.property_read::<u32>(c_str!("test,u32-prop"))?;
+        let prop: u32 = dev.property_read(c_str!("test,u32-prop"))?;
+        dev_info!(dev, "'test,u32-prop' is {:#x}\n", prop);
+
+        let prop: [i16; 4] = dev.property_read_array(c_str!("test,i16-array"))?;
+        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 drvdata = KBox::new(Self { pdev: pdev.clone() }, GFP_KERNEL)?;
 
         Ok(drvdata.into())

-- 
2.45.2

On 25.10.2024 23:05, Rob Herring (Arm) wrote:
> Add some example usage of the device property read methods for
> DT/ACPI/swnode properties.
> 
> Signed-off-by: Rob Herring (Arm) <robh@kernel.org>


I think that we should mention that this works only with 
CONFIG_OF_UNITTEST enabled? And/or maybe wrap the whole somehow with

#[cfg(CONFIG_OF_UNITTEST)]

?

> ---
>   drivers/of/unittest-data/tests-platform.dtsi |  3 +++
>   samples/rust/rust_driver_platform.rs         | 22 ++++++++++++++++++++++
>   2 files changed, 25 insertions(+)
> 
> diff --git a/drivers/of/unittest-data/tests-platform.dtsi b/drivers/of/unittest-data/tests-platform.dtsi
> index 2caaf1c10ee6..a5369b9343b8 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 5cf4a8f86c13..95c290806862 100644
> --- a/samples/rust/rust_driver_platform.rs
> +++ b/samples/rust/rust_driver_platform.rs
> @@ -41,6 +41,28 @@ fn probe(pdev: &mut platform::Device, info: Option<&Self::IdInfo>) -> Result<Pin
>               }
>           };
>   
> +        let dev = pdev.as_ref();


Maybe move this up and use it in Danilo's part, as well? To stay consistent?

--- a/samples/rust/rust_driver_platform.rs
+++ b/samples/rust/rust_driver_platform.rs
@@ -26,25 +26,25 @@ impl platform::Driver for SampleDriver {

      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();

          match (Self::of_match_device(pdev), info) {
              (Some(id), Some(info)) => {
                  dev_info!(
-                    pdev.as_ref(),
+                    dev,
                      "Probed by OF compatible match: '{}' with info: 
'{}'.\n",
                      id.compatible(),
                      info.0
                  );
              }
              _ => {
-                dev_info!(pdev.as_ref(), "Probed by name.\n");
+                dev_info!(dev, "Probed by name.\n");
              }
          };

-        let dev = pdev.as_ref();
          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);
+            dev_info!(dev, "matched compatible string idx = {}\n", idx);
          }

          let prop = dev.property_read_bool(c_str!("test,bool-prop"));
@@ -56,12 +56,10 @@ fn probe(pdev: &mut platform::Device, info: 
Option<&Self::IdInfo>) -> Result<Pin


> +        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);
> +        }
> +
> +        let prop = dev.property_read_bool(c_str!("test,bool-prop"));

I stopped reading here with "hey, "test,bool-prop" isn't in the 
tests-platform.dtsi above, no?". Until I realized that this is 
intentional to get back false. So whats about adding a comment like

// Intentionally check for an non-existent property to get back false

?


> +        dev_info!(dev, "bool prop is {}\n", prop);
> +
> +        let _prop = dev.property_read::<u32>(c_str!("test,u32-prop"))?;
> +        let prop: u32 = dev.property_read(c_str!("test,u32-prop"))?;
> +        dev_info!(dev, "'test,u32-prop' is {:#x}\n", prop);
> +
> +        let prop: [i16; 4] = dev.property_read_array(c_str!("test,i16-array"))?;
> +        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()


In the error case unwrap() (or expect()) will result in panic(). Besides 
some very rare cases I don't see a reason why device drivers should 
panic. Esp. not if reading some array length from the device tree fails 
;) So I don't think we should encourage using unwrap() or expect() in 
drivers by using them even in example code. Which most probably will be 
copied quite often, then ;)

What's about anything like this instead?

          let prop: [i16; 4] = 
dev.property_read_array(c_str!("test,i16-array"))?;
          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 len = dev.property_count_elem::<u16>(c_str!("test,i16-array"));
+        if let Ok(length) = len {
+            dev_info!(dev, "'test,i16-array' length is {}\n", length);
+        }

          let drvdata = KBox::new(Self { pdev: pdev.clone() }, GFP_KERNEL)?;

Or if we want a reasonable error message in the error case, as well, we 
could switch to a match, instead.

Best regards

Dirk



> +        );
> +
>           let drvdata = KBox::new(Self { pdev: pdev.clone() }, GFP_KERNEL)?;
>   
>           Ok(drvdata.into())
>