Add a sample to the samples folder, demonstrating the intended use of the
rust configfs API.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 samples/rust/Kconfig          |  11 +++
 samples/rust/Makefile         |   1 +
 samples/rust/rust_configfs.rs | 179 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 191 insertions(+)

diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index 918dbead2c0b..2f97bf9a7b4c 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -10,6 +10,17 @@ menuconfig SAMPLES_RUST
 
 if SAMPLES_RUST
 
+config SAMPLE_RUST_CONFIGFS
+	tristate "Configfs sample"
+	depends on CONFIGFS_FS
+	help
+	  This option builds the Rust configfs sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_configfs.
+
+	  If unsure, say N.
+
 config SAMPLE_RUST_MINIMAL
 	tristate "Minimal"
 	help
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index 5a8ab0df0567..72122f010caf 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE)		+= rust_misc_device.o
 obj-$(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
+obj-$(CONFIG_SAMPLE_RUST_CONFIGFS)		+= rust_configfs.o
 
 rust_print-y := rust_print_main.o rust_print_events.o
 
diff --git a/samples/rust/rust_configfs.rs b/samples/rust/rust_configfs.rs
new file mode 100644
index 000000000000..36a2c848a979
--- /dev/null
+++ b/samples/rust/rust_configfs.rs
@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust configfs sample.
+
+use kernel::alloc::flags;
+use kernel::c_str;
+use kernel::configfs;
+use kernel::configfs_attrs;
+use kernel::new_mutex;
+use kernel::page::PAGE_SIZE;
+use kernel::prelude::*;
+use kernel::sync::Mutex;
+
+module! {
+    type: RustConfigfs,
+    name: "rust_configfs",
+    author: "Rust for Linux Contributors",
+    description: "Rust configfs sample",
+    license: "GPL",
+}
+
+#[pin_data]
+struct RustConfigfs {
+    #[pin]
+    config: configfs::Subsystem<Configuration>,
+}
+
+#[pin_data]
+struct Configuration {
+    message: &'static CStr,
+    #[pin]
+    bar: Mutex<(KBox<[u8; PAGE_SIZE]>, usize)>,
+}
+
+impl Configuration {
+    fn new() -> impl PinInit<Self, Error> {
+        try_pin_init!(Self {
+            message: c_str!("Hello World\n"),
+            bar <- new_mutex!((KBox::new([0; PAGE_SIZE], flags::GFP_KERNEL)?, 0)),
+        })
+    }
+}
+
+impl kernel::InPlaceModule for RustConfigfs {
+    fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
+        pr_info!("Rust configfs sample (init)\n");
+
+        let item_type = configfs_attrs! {
+            container: configfs::Subsystem<Configuration>,
+            data: Configuration,
+            child: Child,
+            attributes: [
+                message: 0,
+                bar: 1,
+            ],
+        };
+
+        try_pin_init!(Self {
+            config <- configfs::Subsystem::new(
+                c_str!("rust_configfs"), item_type, Configuration::new()
+            ),
+        })
+    }
+}
+
+#[vtable]
+impl configfs::GroupOperations for Configuration {
+    type Child = Child;
+
+    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<Child>, Error>> {
+        let tpe = configfs_attrs! {
+            container: configfs::Group<Child>,
+            data: Child,
+            child: GrandChild,
+            attributes: [
+                baz: 0,
+            ],
+        };
+
+        Ok(configfs::Group::new(name.try_into()?, tpe, Child::new()))
+    }
+}
+
+#[vtable]
+impl configfs::AttributeOperations<0> for Configuration {
+    type Data = Configuration;
+
+    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+        pr_info!("Show message\n");
+        let data = container.message;
+        page[0..data.len()].copy_from_slice(data);
+        Ok(data.len())
+    }
+}
+
+#[vtable]
+impl configfs::AttributeOperations<1> for Configuration {
+    type Data = Configuration;
+
+    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+        pr_info!("Show bar\n");
+        let guard = container.bar.lock();
+        let data = guard.0.as_slice();
+        let len = guard.1;
+        page[0..len].copy_from_slice(&data[0..len]);
+        Ok(len)
+    }
+
+    fn store(container: &Configuration, page: &[u8]) -> Result {
+        pr_info!("Store bar\n");
+        let mut guard = container.bar.lock();
+        guard.0[0..page.len()].copy_from_slice(page);
+        guard.1 = page.len();
+        Ok(())
+    }
+}
+
+#[pin_data]
+struct Child {}
+
+impl Child {
+    fn new() -> impl PinInit<Self, Error> {
+        try_pin_init!(Self {})
+    }
+}
+
+#[vtable]
+impl configfs::GroupOperations for Child {
+    type Child = GrandChild;
+
+    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<GrandChild>, Error>> {
+        let tpe = configfs_attrs! {
+            container: configfs::Group<GrandChild>,
+            data: GrandChild,
+            attributes: [
+                gc: 0,
+            ],
+        };
+
+        Ok(configfs::Group::new(
+            name.try_into()?,
+            tpe,
+            GrandChild::new(),
+        ))
+    }
+}
+
+#[vtable]
+impl configfs::AttributeOperations<0> for Child {
+    type Data = Child;
+
+    fn show(_container: &Child, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+        pr_info!("Show baz\n");
+        let data = c"Hello Baz\n".to_bytes();
+        page[0..data.len()].copy_from_slice(data);
+        Ok(data.len())
+    }
+}
+
+#[pin_data]
+struct GrandChild {}
+
+impl GrandChild {
+    fn new() -> impl PinInit<Self, Error> {
+        try_pin_init!(Self {})
+    }
+}
+
+#[vtable]
+impl configfs::AttributeOperations<0> for GrandChild {
+    type Data = GrandChild;
+
+    fn show(_container: &GrandChild, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+        pr_info!("Show baz\n");
+        let data = c"Hello GC\n".to_bytes();
+        page[0..data.len()].copy_from_slice(data);
+        Ok(data.len())
+    }
+}

-- 
2.47.0

Hi Andreas,

> On 24 Feb 2025, at 10:21, Andreas Hindborg <a.hindborg@kernel.org> wrote:
> 
> Add a sample to the samples folder, demonstrating the intended use of the
> rust configfs API.

nit: this is not the first time I see Rust not capitalized in this series.

> 
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
> samples/rust/Kconfig          |  11 +++
> samples/rust/Makefile         |   1 +
> samples/rust/rust_configfs.rs | 179 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 191 insertions(+)
> 
> diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
> index 918dbead2c0b..2f97bf9a7b4c 100644
> --- a/samples/rust/Kconfig
> +++ b/samples/rust/Kconfig
> @@ -10,6 +10,17 @@ menuconfig SAMPLES_RUST
> 
> if SAMPLES_RUST
> 
> +config SAMPLE_RUST_CONFIGFS
> + tristate "Configfs sample"
> + depends on CONFIGFS_FS
> + help
> +  This option builds the Rust configfs sample.
> +
> +  To compile this as a module, choose M here:
> +  the module will be called rust_configfs.
> +
> +  If unsure, say N.
> +
> config SAMPLE_RUST_MINIMAL
> tristate "Minimal"
> help
> diff --git a/samples/rust/Makefile b/samples/rust/Makefile
> index 5a8ab0df0567..72122f010caf 100644
> --- a/samples/rust/Makefile
> +++ b/samples/rust/Makefile
> @@ -6,6 +6,7 @@ obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE) += rust_misc_device.o
> obj-$(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
> +obj-$(CONFIG_SAMPLE_RUST_CONFIGFS) += rust_configfs.o
> 
> rust_print-y := rust_print_main.o rust_print_events.o
> 
> diff --git a/samples/rust/rust_configfs.rs b/samples/rust/rust_configfs.rs
> new file mode 100644
> index 000000000000..36a2c848a979
> --- /dev/null
> +++ b/samples/rust/rust_configfs.rs
> @@ -0,0 +1,179 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Rust configfs sample.
> +
> +use kernel::alloc::flags;
> +use kernel::c_str;
> +use kernel::configfs;
> +use kernel::configfs_attrs;
> +use kernel::new_mutex;
> +use kernel::page::PAGE_SIZE;
> +use kernel::prelude::*;
> +use kernel::sync::Mutex;
> +
> +module! {
> +    type: RustConfigfs,
> +    name: "rust_configfs",
> +    author: "Rust for Linux Contributors",
> +    description: "Rust configfs sample",
> +    license: "GPL",
> +}
> +
> +#[pin_data]
> +struct RustConfigfs {
> +    #[pin]
> +    config: configfs::Subsystem<Configuration>,
> +}
> +
> +#[pin_data]
> +struct Configuration {
> +    message: &'static CStr,
> +    #[pin]
> +    bar: Mutex<(KBox<[u8; PAGE_SIZE]>, usize)>,
> +}
> +
> +impl Configuration {
> +    fn new() -> impl PinInit<Self, Error> {
> +        try_pin_init!(Self {
> +            message: c_str!("Hello World\n"),
> +            bar <- new_mutex!((KBox::new([0; PAGE_SIZE], flags::GFP_KERNEL)?, 0)),
> +        })
> +    }
> +}
> +
> +impl kernel::InPlaceModule for RustConfigfs {
> +    fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
> +        pr_info!("Rust configfs sample (init)\n");
> +
> +        let item_type = configfs_attrs! {
> +            container: configfs::Subsystem<Configuration>,
> +            data: Configuration,
> +            child: Child,
> +            attributes: [
> +                message: 0,
> +                bar: 1,
> +            ],
> +        };

As I said in the previous patch, this macro is a bit complex. Is there anything more you can do with it?

If so, it better be in this driver, because I hardly think anybody will go through the source code itself
to figure out. My 2c.


> +
> +        try_pin_init!(Self {
> +            config <- configfs::Subsystem::new(
> +                c_str!("rust_configfs"), item_type, Configuration::new()
> +            ),
> +        })
> +    }
> +}
> +
> +#[vtable]
> +impl configfs::GroupOperations for Configuration {
> +    type Child = Child;
> +
> +    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<Child>, Error>> {
> +        let tpe = configfs_attrs! {
> +            container: configfs::Group<Child>,
> +            data: Child,
> +            child: GrandChild,
> +            attributes: [
> +                baz: 0,
> +            ],
> +        };
> +
> +        Ok(configfs::Group::new(name.try_into()?, tpe, Child::new()))
> +    }
> +}
> +
> +#[vtable]
> +impl configfs::AttributeOperations<0> for Configuration {
> +    type Data = Configuration;
> +
> +    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
> +        pr_info!("Show message\n");
> +        let data = container.message;
> +        page[0..data.len()].copy_from_slice(data);
> +        Ok(data.len())
> +    }
> +}
> +
> +#[vtable]
> +impl configfs::AttributeOperations<1> for Configuration {
> +    type Data = Configuration;
> +
> +    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
> +        pr_info!("Show bar\n");
> +        let guard = container.bar.lock();
> +        let data = guard.0.as_slice();
> +        let len = guard.1;
> +        page[0..len].copy_from_slice(&data[0..len]);
> +        Ok(len)
> +    }
> +
> +    fn store(container: &Configuration, page: &[u8]) -> Result {
> +        pr_info!("Store bar\n");
> +        let mut guard = container.bar.lock();
> +        guard.0[0..page.len()].copy_from_slice(page);
> +        guard.1 = page.len();
> +        Ok(())
> +    }
> +}
> +
> +#[pin_data]
> +struct Child {}

nit: you don’t need the braces here

> +
> +impl Child {
> +    fn new() -> impl PinInit<Self, Error> {
> +        try_pin_init!(Self {})
> +    }
> +}
> +
> +#[vtable]
> +impl configfs::GroupOperations for Child {
> +    type Child = GrandChild;
> +
> +    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<GrandChild>, Error>> {
> +        let tpe = configfs_attrs! {
> +            container: configfs::Group<GrandChild>,
> +            data: GrandChild,
> +            attributes: [
> +                gc: 0,
> +            ],
> +        };
> +
> +        Ok(configfs::Group::new(
> +            name.try_into()?,
> +            tpe,
> +            GrandChild::new(),
> +        ))
> +    }
> +}
> +
> +#[vtable]
> +impl configfs::AttributeOperations<0> for Child {
> +    type Data = Child;
> +
> +    fn show(_container: &Child, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
> +        pr_info!("Show baz\n");
> +        let data = c"Hello Baz\n".to_bytes();
> +        page[0..data.len()].copy_from_slice(data);
> +        Ok(data.len())
> +    }
> +}
> +
> +#[pin_data]
> +struct GrandChild {}

…nor here

> +
> +impl GrandChild {
> +    fn new() -> impl PinInit<Self, Error> {
> +        try_pin_init!(Self {})
> +    }
> +}
> +
> +#[vtable]
> +impl configfs::AttributeOperations<0> for GrandChild {
> +    type Data = GrandChild;
> +
> +    fn show(_container: &GrandChild, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
> +        pr_info!("Show baz\n");

As I said in the cover letter, perhaps this one slip through :)

> +        let data = c"Hello GC\n".to_bytes();
> +        page[0..data.len()].copy_from_slice(data);
> +        Ok(data.len())
> +    }
> +}
> 
> -- 
> 2.47.0
> 
> 

I’m OK with this patch. It works, and it does what it’s supposed to do, i.e.: showcase the API.

With the “Show baz” nit fixed:

Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>

"Daniel Almeida" <daniel.almeida@collabora.com> writes:

> Hi Andreas,
>
>> On 24 Feb 2025, at 10:21, Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> Add a sample to the samples folder, demonstrating the intended use of the
>> rust configfs API.
>
> nit: this is not the first time I see Rust not capitalized in this series.

Will fix 👍

[...]

>> +impl kernel::InPlaceModule for RustConfigfs {
>> +    fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
>> +        pr_info!("Rust configfs sample (init)\n");
>> +
>> +        let item_type = configfs_attrs! {
>> +            container: configfs::Subsystem<Configuration>,
>> +            data: Configuration,
>> +            child: Child,
>> +            attributes: [
>> +                message: 0,
>> +                bar: 1,
>> +            ],
>> +        };
>
> As I said in the previous patch, this macro is a bit complex. Is there anything more you can do with it?
>
> If so, it better be in this driver, because I hardly think anybody will go through the source code itself
> to figure out. My 2c.

I can add some inline comments on the usage here. Is that what you are
thinking of?

>
>
>> +
>> +        try_pin_init!(Self {
>> +            config <- configfs::Subsystem::new(
>> +                c_str!("rust_configfs"), item_type, Configuration::new()
>> +            ),
>> +        })
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::GroupOperations for Configuration {
>> +    type Child = Child;
>> +
>> +    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<Child>, Error>> {
>> +        let tpe = configfs_attrs! {
>> +            container: configfs::Group<Child>,
>> +            data: Child,
>> +            child: GrandChild,
>> +            attributes: [
>> +                baz: 0,
>> +            ],
>> +        };
>> +
>> +        Ok(configfs::Group::new(name.try_into()?, tpe, Child::new()))
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<0> for Configuration {
>> +    type Data = Configuration;
>> +
>> +    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show message\n");
>> +        let data = container.message;
>> +        page[0..data.len()].copy_from_slice(data);
>> +        Ok(data.len())
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<1> for Configuration {
>> +    type Data = Configuration;
>> +
>> +    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show bar\n");
>> +        let guard = container.bar.lock();
>> +        let data = guard.0.as_slice();
>> +        let len = guard.1;
>> +        page[0..len].copy_from_slice(&data[0..len]);
>> +        Ok(len)
>> +    }
>> +
>> +    fn store(container: &Configuration, page: &[u8]) -> Result {
>> +        pr_info!("Store bar\n");
>> +        let mut guard = container.bar.lock();
>> +        guard.0[0..page.len()].copy_from_slice(page);
>> +        guard.1 = page.len();
>> +        Ok(())
>> +    }
>> +}
>> +
>> +#[pin_data]
>> +struct Child {}
>
> nit: you don’t need the braces here

Can't do that. The `pin_data` macro won't eat it. I'll add a comment.

>
>> +
>> +impl Child {
>> +    fn new() -> impl PinInit<Self, Error> {
>> +        try_pin_init!(Self {})
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::GroupOperations for Child {
>> +    type Child = GrandChild;
>> +
>> +    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<GrandChild>, Error>> {
>> +        let tpe = configfs_attrs! {
>> +            container: configfs::Group<GrandChild>,
>> +            data: GrandChild,
>> +            attributes: [
>> +                gc: 0,
>> +            ],
>> +        };
>> +
>> +        Ok(configfs::Group::new(
>> +            name.try_into()?,
>> +            tpe,
>> +            GrandChild::new(),
>> +        ))
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<0> for Child {
>> +    type Data = Child;
>> +
>> +    fn show(_container: &Child, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show baz\n");
>> +        let data = c"Hello Baz\n".to_bytes();
>> +        page[0..data.len()].copy_from_slice(data);
>> +        Ok(data.len())
>> +    }
>> +}
>> +
>> +#[pin_data]
>> +struct GrandChild {}
>
> …nor here

>
>> +
>> +impl GrandChild {
>> +    fn new() -> impl PinInit<Self, Error> {
>> +        try_pin_init!(Self {})
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<0> for GrandChild {
>> +    type Data = GrandChild;
>> +
>> +    fn show(_container: &GrandChild, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show baz\n");
>
> As I said in the cover letter, perhaps this one slip through :)

Yes, thank you.

>
>> +        let data = c"Hello GC\n".to_bytes();
>> +        page[0..data.len()].copy_from_slice(data);
>> +        Ok(data.len())
>> +    }
>> +}
>>
>> --
>> 2.47.0
>>
>>
>
> I’m OK with this patch. It works, and it does what it’s supposed to do, i.e.: showcase the API.
>
> With the “Show baz” nit fixed:
>
> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>

Thanks!


Best regards,
Andreas Hindborg

>> 
>> As I said in the previous patch, this macro is a bit complex. Is there anything more you can do with it?
>> 
>> If so, it better be in this driver, because I hardly think anybody will go through the source code itself
>> to figure out. My 2c.
> 
> I can add some inline comments on the usage here. Is that what you are
> thinking of?
> 

That can’t hurt, but my point is, if you can think of any other example that is substantially different from
what you have, include it, specially if it involves some different syntax somehow.

Otherwise this is fine as is.

— Daniel