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 C62891E1022; Fri, 6 Dec 2024 09:29:16 +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=1733477357; cv=none; b=gUV14L+y+v5zfVosODhF8k6EXECFrCXLaC+nMNubBKsLmPohL1ZKIJ3K+GgFRHy9fFsk6C1l7/I+Glt3rFbCUD5h6GjAlfsIS6FrwQcNU15HhxXbfYHu1pq5dzIuMixhCiJKyPvZXwkl0EoyTYSKORM6c//RvMn5/NIFgfvzy4g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733477357; c=relaxed/simple; bh=bDttRsnyVJw/ISB0XyqLGm2dkQcrbpIOGlqcwn0yjps=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i+4ayfGU3oT9fLlGkf19Q6wDMO01GtzTBGUHZLcjZYdvOos1IiFe7/qSaH07NhpyfC2AIBNh9hMiL+RV5v6jP3Ww0D5L0caJMuF4ybRjk+Laq4oa7LPWLHtkDqHdXyZ+BprQapjfSZtOJMbpqGV2h6hCPE30sRvA9HNF4kWm2tg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=a2JYy2jj; 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="a2JYy2jj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E4E8AC4CED1; Fri, 6 Dec 2024 09:29:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733477356; bh=bDttRsnyVJw/ISB0XyqLGm2dkQcrbpIOGlqcwn0yjps=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=a2JYy2jjS/gVqj16h3fI9c7eMU3tb10aK/4TxGX4rAqd36KHCnHKmbTxfSvFXp1FT AMN897nnw62yg2/AbTb+oXq7zjR1dlWRwj6QJdJH5O9zCZZDtvIXBTAuqUOuqj1KHC 0aDBgInEPyx5uD9lIgp9ZddMzwcZd4WoeciUmmCjANY6I8YSIUBRSes/QuLvjyS03H QB0qd4Fo+v0/0QK+GMavbQPaezcC0aYzCyB7WVDeE6PTfI6pqQTv864Vb+ON0rP6y+ TIl1KtT9FQnMmHb9NtdRKAQcoulrBqWdL6ecr6meCPRVcs6Ku6Lpy0h5QdXdvNAQyP 3QF50eQBKG6HA== Date: Fri, 6 Dec 2024 10:29:07 +0100 From: Danilo Krummrich To: Lee Jones Cc: linux-kernel@vger.kernel.org, arnd@arndb.de, gregkh@linuxfoundation.org, 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 v4 2/4] samples: rust: Provide example using the new Rust MiscDevice abstraction Message-ID: References: <20241206090515.752267-1-lee@kernel.org> <20241206090515.752267-5-lee@kernel.org> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241206090515.752267-5-lee@kernel.org> On Fri, Dec 06, 2024 at 09:05:06AM +0000, Lee Jones wrote: > This sample driver demonstrates the following basic operations: > > * Register a Misc Device > * Create /dev/rust-misc-device > * Provide open call-back for the aforementioned character device > * Operate on the character device via a simple ioctl() > * Provide close call-back for 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..3837532d259e > --- /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('|' 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, > + )?, > + }) Since this v4 was sent just when I was commenting on v3: Why do we add examples where we ask people to allocate those structures with kmalloc()? `MiscDevice` should switch to the generic `Registration` type in [1] and use `InPlaceModule`, such that those structures land in the .data section of the binary. [1] https://lore.kernel.org/rust-for-linux/20241205141533.111830-3-dakr@kernel.org/ > + } > +} > + > +struct RustMiscDevice; > + > +#[vtable] > +impl MiscDevice for RustMiscDevice { > + type Ptr = KBox; > + > + fn open() -> Result> { > + pr_info!("Opening Rust Misc Device Sample\n"); This should be `dev_info!`, but I see why you don't have access to the device structure here... @Greg: How do miscdev drivers do this in C? I looked at a couple of them, but all of those seem to use pr_* macros. They can't get the device pointer from the inode or file pointer. However, C drivers could refer to the struct miscdevice directly since it's almost always a static variable in the file scope. In Rust we do the static allocation part with `InPlaceModule` as mentioned above. However, this still doesn't let us refer to the underlying struct miscdevice. This all would be much cleaner if there'd be a "fake" probe() callback for a struct miscdevice. This way we could perfectly align the miscdevice abstraction with the abstractions for all other drivers, such as PCI, platform, etc. - Danilo > + > + 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(ENOTTY); > + } > + } > + > + Ok(0) > + } > +} > + > +impl Drop for RustMiscDevice { > + fn drop(&mut self) { > + pr_info!("Exiting the Rust Misc Device Sample\n"); > + } > +} > -- > 2.47.0.338.g60cca15819-goog > >