Re: [PATCH v4 13/13] samples: rust: add Rust platform sample driver

Danilo Krummrich
2024-12-06T08:33:37Z

On Thu, Dec 05, 2024 at 06:09:10PM +0100, Dirk Behme wrote:
> Hi Danilo,
>
> On 05.12.24 15:14, Danilo Krummrich wrote:
> > Add a sample Rust platform driver illustrating the usage of the platform
> > bus abstractions.
> >
> > This driver probes through either a match of device / driver name or a
> > match within the OF ID table.
> >
> > Signed-off-by: Danilo Krummrich <dakr@kernel.org>
>
> Not a review comment, but a question/proposal:
>
> What do you think to convert the platform sample into an example/test?
> And drop it in samples/rust then? Like [1] below?

Generally, I think doctests are indeed preferrable. In this particular case
though, I think it's better to have a sample module, since this way it can serve
as go-to example of how to write a platform driver in Rust.

Especially for (kernel) folks who do not have a Rust (for Linux) background it's
way more accessible.

>
> We would have (a) a complete example in the documentation and (b) some
> (KUnit) test coverage and (c) have one patch less in the series and
> (d) one file less to maintain long term.
>
> I think to remember that it was mentioned somewhere that a
> documentation example / KUnit test is preferred over samples/rust (?).
>
> Just an idea :)
>
> Best regards
>
> Dirk
>
> [1]
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ae576c842c51..365fc48b7041 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7035,7 +7035,6 @@ F: rust/kernel/device_id.rs
> F: rust/kernel/devres.rs
> F: rust/kernel/driver.rs
> F: rust/kernel/platform.rs
> -F: samples/rust/rust_driver_platform.rs
>
> DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
> M: Nishanth Menon <nm@ti.com>
> diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
> index 868cfddb75a2..77aeb6fc2120 100644
> --- a/rust/kernel/platform.rs
> +++ b/rust/kernel/platform.rs
> @@ -142,30 +142,55 @@ macro_rules! module_platform_driver {
> /// # Example
> ///
> ///```
> -/// # use kernel::{bindings, c_str, of, platform};
> +/// # mod mydriver {
> +/// #
> +/// # // Get this into the scope of the module to make the
> assert_eq!() buildable
> +/// # static __DOCTEST_ANCHOR: i32 = core::line!() as i32 - 4;
> +/// #
> +/// # use kernel::{c_str, of, platform, prelude::*};
> +/// #
> +/// struct MyDriver {
> +/// pdev: platform::Device,
> +/// }
> ///
> -/// struct MyDriver;
> +/// struct Info(u32);
> ///
> /// kernel::of_device_table!(
> /// OF_TABLE,
> /// MODULE_OF_TABLE,
> /// <MyDriver as platform::Driver>::IdInfo,
> -/// [
> -/// (of::DeviceId::new(c_str!("test,device")), ())
> -/// ]
> +/// [(of::DeviceId::new(c_str!("test,rust-device")), Info(42))]
> /// );
> ///
> /// impl platform::Driver for MyDriver {
> -/// type IdInfo = ();
> +/// type IdInfo = Info;
> /// const OF_ID_TABLE: platform::IdTable<Self::IdInfo> = &OF_TABLE;
> ///
> -/// fn probe(
> -/// _pdev: &mut platform::Device,
> -/// _id_info: Option<&Self::IdInfo>,
> -/// ) -> Result<Pin<KBox<Self>>> {
> -/// Err(ENODEV)
> +/// 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");
> +///
> +/// assert_eq!(info.unwrap().0, 42);
> +///
> +/// let drvdata = KBox::new(Self { pdev: pdev.clone() },
> GFP_KERNEL)?;
> +///
> +/// Ok(drvdata.into())
> +/// }
> +/// }
> +///
> +/// impl Drop for MyDriver {
> +/// fn drop(&mut self) {
> +/// dev_dbg!(self.pdev.as_ref(), "Remove Rust Platform driver
> sample.\n");
> /// }
> /// }
> +///
> +/// kernel::module_platform_driver! {
> +/// type: MyDriver,
> +/// name: "rust_driver_platform",
> +/// author: "Danilo Krummrich",
> +/// description: "Rust Platform driver",
> +/// license: "GPL v2",
> +/// }
> +/// # }
> ///```
> pub trait Driver {
> /// The type holding information about each device id supported
> by the driver.
> diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
> index 70126b750426..6d468193cdd8 100644
> --- a/samples/rust/Kconfig
> +++ b/samples/rust/Kconfig
> @@ -41,16 +41,6 @@ config SAMPLE_RUST_DRIVER_PCI
>
> If unsure, say N.
>
> -config SAMPLE_RUST_DRIVER_PLATFORM
> - tristate "Platform Driver"
> - help
> - This option builds the Rust Platform driver sample.
> -
> - To compile this as a module, choose M here:
> - the module will be called rust_driver_platform.
> -
> - If unsure, say N.
> -
> config SAMPLE_RUST_HOSTPROGS
> bool "Host programs"
> help
> diff --git a/samples/rust/Makefile b/samples/rust/Makefile
> index 761d13fff018..2f5b6bdb2fa5 100644
> --- a/samples/rust/Makefile
> +++ b/samples/rust/Makefile
> @@ -4,7 +4,6 @@ ccflags-y += -I$(src) # needed for trace events
> obj-$(CONFIG_SAMPLE_RUST_MINIMAL) += rust_minimal.o
> obj-$(CONFIG_SAMPLE_RUST_PRINT) += rust_print.o
> obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI) += rust_driver_pci.o
> -obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM) += rust_driver_platform.o
>
> rust_print-y := rust_print_main.o rust_print_events.o
>
> diff --git a/samples/rust/rust_driver_platform.rs
> b/samples/rust/rust_driver_platform.rs
> deleted file mode 100644
> index 2f0dbbe69e10..000000000000
> --- a/samples/rust/rust_driver_platform.rs
> +++ /dev/null
> @@ -1,49 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -
> -//! Rust Platform driver sample.
> -
> -use kernel::{c_str, of, platform, prelude::*};
> -
> -struct SampleDriver {
> - pdev: platform::Device,
> -}
> -
> -struct Info(u32);
> -
> -kernel::of_device_table!(
> - OF_TABLE,
> - MODULE_OF_TABLE,
> - <SampleDriver as platform::Driver>::IdInfo,
> - [(of::DeviceId::new(c_str!("test,rust-device")), Info(42))]
> -);
> -
> -impl platform::Driver for SampleDriver {
> - type IdInfo = Info;
> - const OF_ID_TABLE: platform::IdTable<Self::IdInfo> = &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");
> -
> - if let Some(info) = info {
> - dev_info!(pdev.as_ref(), "Probed with info: '{}'.\n",
> info.0);
> - }
> -
> - let drvdata = KBox::new(Self { pdev: pdev.clone() },
> GFP_KERNEL)?;
> -
> - Ok(drvdata.into())
> - }
> -}
> -
> -impl Drop for SampleDriver {
> - fn drop(&mut self) {
> - dev_dbg!(self.pdev.as_ref(), "Remove Rust Platform driver
> sample.\n");
> - }
> -}
> -
> -kernel::module_platform_driver! {
> - type: SampleDriver,
> - name: "rust_driver_platform",
> - author: "Danilo Krummrich",
> - description: "Rust Platform driver",
> - license: "GPL v2",
> -}
>