From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D535F1DA0E9; Fri, 6 Dec 2024 07:13:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733469181; cv=none; b=qKyyji76H54EX5tv5nKIlnfwK9Qt7PeUWf7j3RhDyn2HfT5Cepy0e9osiIs0/KTdyH8j1hnL6We3VrebTDEo1nF7o8BUaD33unb5Z5S71ExAO0e4Sl7kLzSBcClrU1nWFH347TFEM7a6NNmXd5r3Yiz6wZtQJfti0DBBdV8Xlcg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733469181; c=relaxed/simple; bh=E7BtaM4w2sZ9Ofgw+4DsejwJANfQSqIJgDgyOLUYe1o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dxbPkrOpQdJrWl7rgRo1Rb54qb8I7FyVvAivJMZYvBvvfzdYZuyirwScutaiH7XR4Juy2IDg/j9WD1wfPjJtBCbadlzUu9HRu4Qxel2ooQW0Okup1nQvbWV45/9WaIvss8ycmC40IiRWyI0umeaFCJXqt0+U/2+L7GIG/dLLTKo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NrdeLKgv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NrdeLKgv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F350FC4CED1; Fri, 6 Dec 2024 07:12:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733469181; bh=E7BtaM4w2sZ9Ofgw+4DsejwJANfQSqIJgDgyOLUYe1o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NrdeLKgv1bEVeuse7guIYPKovP0S68PQMjxNy2EFpm0F3o62fXiv8/JLVo7kel+w/ 3Ap8tIwqwGhC1aAcEM2RLP1xYkxhlcJxZ3GwRO9lBgED7GvgmKDa1GZ/yFrpf+18b8 tF2KiCVq1stc4XLD3bYVS6HQXOkgX85MM0sEJ/4LFXk24BN+tyuJ1ACn5pEneEeYQe vsQ6UYYFxAxgWqyAMB/93KuMvZ6Nv2At7U5IYNcM2uBGQE2ffvlLuY/xBviRvz62Qt l8+SDqZRR79s/LDiCoV6KtE/ia0ow+BohgBYRRMh+QyXyafHqcZux4qVwsQZfy0+yS x4LIgCeD8fYaA== Date: Fri, 6 Dec 2024 07:12:56 +0000 From: Lee Jones To: Greg KH Cc: linux-kernel@vger.kernel.org, arnd@arndb.de, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, rust-for-linux@vger.kernel.org Subject: Re: [PATCH v3 3/5] samples: rust: Provide example using the new Rust MiscDevice abstraction Message-ID: <20241206071256.GB8882@google.com> References: <20241205162531.1883859-1-lee@kernel.org> <20241205162531.1883859-4-lee@kernel.org> <2024120642-trend-omnivore-69d3@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2024120642-trend-omnivore-69d3@gregkh> On Fri, 06 Dec 2024, Greg KH wrote: > On Thu, Dec 05, 2024 at 04:25:20PM +0000, Lee Jones 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 > > --- > > samples/rust/Kconfig | 10 ++++ > > samples/rust/Makefile | 1 + > > samples/rust/rust_misc_device.rs | 80 ++++++++++++++++++++++++++++++++ > > 3 files changed, 91 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..f50925713f1a > > --- /dev/null > > +++ b/samples/rust/rust_misc_device.rs > > @@ -0,0 +1,80 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > + > > +// Copyright (C) 2024 Google LLC. > > + > > +//! 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>>, > > +} > > + > > +impl kernel::Module for RustMiscDeviceModule { > > + fn init(_module: &'static ThisModule) -> Result { > > + pr_info!("Initialising Rust Misc Device Sample\n"); > > + > > + let options = MiscDeviceOptions { > > + name: c_str!("rust-misc-device"), > > + }; > > + > > + Ok(Self { > > + _miscdev: KBox::pin_init( > > + MiscDeviceRegistration::::register(options), > > + GFP_KERNEL, > > + )?, > > + }) > > + } > > +} > > + > > +struct RustMiscDevice; > > + > > +#[vtable] > > +impl MiscDevice for RustMiscDevice { > > + type Ptr = KBox; > > + > > + fn open() -> Result> { > > + pr_info!("Opening Rust Misc Device Sample\n"); > > + > > + Ok(KBox::new(RustMiscDevice, GFP_KERNEL)?) > > + } > > + > > + fn ioctl( > > + _device: ::Borrowed<'_>, > > + cmd: u32, > > + _arg: usize, > > + ) -> Result { > > + pr_info!("IOCTLing Rust Misc Device Sample\n"); > > + > > + match cmd { > > + RUST_MISC_DEV_HELLO => pr_info!("Hello from the Rust Misc Device\n"), > > + _ => { > > + pr_err!("IOCTL not recognised: {}\n", cmd); > > + return Err(ENOIOCTLCMD); > > To quote errno.h: > These should never be seen by user programs > > The correct value here is ENOTTY. > > Yeah, fun stuff. Not intuitive at all, sorry. I read the instructions in: Documentation/driver-api/ioctl.rst "When the ioctl callback is called with an unknown command number, the handler returns either -ENOTTY or -ENOIOCTLCMD, which also results in -ENOTTY being returned from the system call. Some subsystems return -ENOSYS or -EINVAL here for historic reasons, but this is wrong." This makes it sound like the system call itself converts one to the other. Either way, I'll make the change. Thanks. -- Lee Jones [李琼斯]