Re: [PATCH 1/2] samples: rust: Provide example using the new Rust MiscDevice abstraction

[Lee Jones <lee@kernel.org>]

On Thu, 05 Dec 2024, Lee Jones wrote:

> On Thu, 05 Dec 2024, Benoît du Garreau wrote:
> 
> > On Wed, 4 Dec 2024 17:46:24 +0000 Lee Jones <lee@kernel.org> wrote:
> > 
> > > This sample driver demonstrates the following basic operations:
> > >
> > > * Register a Misc Device
> > > * Create /dev/rust-misc-device
> > > * Open the aforementioned character device
> > > * Operate on the character device via a simple ioctl()
> > > * Close the character device
> > >
> > > Signed-off-by: Lee Jones <lee@kernel.org>
> > > ---
> > >  samples/rust/Kconfig             | 10 ++++
> > >  samples/rust/Makefile            |  1 +
> > >  samples/rust/rust_misc_device.rs | 84 ++++++++++++++++++++++++++++++++
> > >  3 files changed, 95 insertions(+)
> > >  create mode 100644 samples/rust/rust_misc_device.rs
> > >
> > > diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
> > > index b0f74a81c8f9..df384e679901 100644
> > > --- a/samples/rust/Kconfig
> > > +++ b/samples/rust/Kconfig
> > > @@ -20,6 +20,16 @@ config SAMPLE_RUST_MINIMAL
> > >
> > >  	  If unsure, say N.
> > >
> > > +config SAMPLE_RUST_MISC_DEVICE
> > > +	tristate "Misc device"
> > > +	help
> > > +	  This option builds the Rust misc device.
> > > +
> > > +	  To compile this as a module, choose M here:
> > > +	  the module will be called rust_misc_device.
> > > +
> > > +	  If unsure, say N.
> > > +
> > >  config SAMPLE_RUST_PRINT
> > >  	tristate "Printing macros"
> > >  	help
> > > diff --git a/samples/rust/Makefile b/samples/rust/Makefile
> > > index c1a5c1655395..ad4b97a98580 100644
> > > --- a/samples/rust/Makefile
> > > +++ b/samples/rust/Makefile
> > > @@ -2,6 +2,7 @@
> > >  ccflags-y += -I$(src)				# needed for trace events
> > >
> > >  obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
> > > +obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE)		+= rust_misc_device.o
> > >  obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
> > >
> > >  rust_print-y := rust_print_main.o rust_print_events.o
> > > diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
> > > new file mode 100644
> > > index 000000000000..5f1b69569ef7
> > > --- /dev/null
> > > +++ b/samples/rust/rust_misc_device.rs
> > > @@ -0,0 +1,84 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +
> > > +//! Rust misc device sample.
> > > +
> > > +use kernel::{
> > > +    c_str,
> > > +    ioctl::_IO,
> > > +    miscdevice::{MiscDevice, MiscDeviceOptions, MiscDeviceRegistration},
> > > +    prelude::*,
> > > +};
> > > +
> > > +const RUST_MISC_DEV_HELLO: u32 = _IO('R' as u32, 9);
> > > +
> > > +module! {
> > > +    type: RustMiscDeviceModule,
> > > +    name: "rust_misc_device",
> > > +    author: "Lee Jones",
> > > +    description: "Rust misc device sample",
> > > +    license: "GPL",
> > > +}
> > > +
> > > +struct RustMiscDeviceModule {
> > > +    _miscdev: Pin<KBox<MiscDeviceRegistration<RustMiscDevice>>>,
> > > +}
> > > +
> > > +impl kernel::Module for RustMiscDeviceModule {
> > 
> > This could probably use `kernel::InPlaceModule` and avoid allocating
> > the registration.
> 
> Is there a way to do this and keep the print?

Seeing as this is the concept/API demonstrator, I think what I'd sooner
do, is demonstrate some actual initialisation.  Maybe with a head-nod to
`kernel::InPlaceModule` in a comment.

-- 
Lee Jones [李琼斯]