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Message-ID: <df1473dc-99a4-4a6c-bfc3-09c37b9883d5@de.bosch.com>
Date: Mon, 28 Oct 2024 08:13:59 +0100
From: Dirk Behme <dirk.behme@...bosch.com>
To: "Rob Herring (Arm)" <robh@...nel.org>, Saravana Kannan
<saravanak@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>, 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>, Dirk Behme
<dirk.behme@...il.com>
CC: <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<rust-for-linux@...r.kernel.org>
Subject: Re: [PATCH RFC 3/3] samples: rust: platform: Add property read
examples
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@...nel.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())
>
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