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 5A6241D5173; Thu, 5 Dec 2024 09:47:39 +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=1733392061; cv=none; b=N08Hi2In+A4nVTlXdgM5JlskHZxUzWhT1lZrPCc6yrTHuysQG3IK9aypsJyqPJguR5voM2JtdY5HARDaL8p2Y1+iNLk1FHLveYrwOH00pULuv8+eWR8nmYaCm3D23ZzqtKOijzNkpTu7G5eYK2Y60IrB/j9DWSrnN/c6MPvFpf0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733392061; c=relaxed/simple; bh=GYNvFk3PY77psIQGuKrMGsA4D+7kvXV/P4IV+wMPXk0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XK0gClAD2OKbc9usYRW6/+Wm5D+/eKrEg8kWvpwxAfSnZMCgs2n3xiiIh6xDPZW5DgwuTobYkAhoFTTdhSLcS5sTXyVQZr6CgbDNSHlWoX5yAg6cDUp8QLvdJOcYmlSprjoJ6qTovEZ8caPy7WWcOwxCBX0sYvwpB2aQ2uw6m/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=GTkUBY6H; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="GTkUBY6H" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69E04C4CED6; Thu, 5 Dec 2024 09:47:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1733392057; bh=GYNvFk3PY77psIQGuKrMGsA4D+7kvXV/P4IV+wMPXk0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GTkUBY6HAEZeuwNlxBB5w4lNe3HHVPxj1dENuZJPzLmbU+y+xy+Hmith3SwPYKACG c5+XkpQZYMgME2EsdwHp2c/O50HfVFC7TGtu21pNKBN/UUeysk+4ig++IKBV6+5xQ2 gQo+IY6/uCYQVr7xRSaIj3Y0Axzd9rMN6IzhgcxA= Date: Thu, 5 Dec 2024 10:47:19 +0100 From: Greg KH To: Lee Jones Cc: linux-kernel@vger.kernel.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 2/2] sample: rust_misc_device: Demonstrate additional get/set value functionality Message-ID: <2024120551-sternness-wilder-f417@gregkh> References: <20241204174627.1151288-1-lee@kernel.org> <20241204174627.1151288-2-lee@kernel.org> <2024120453-unfunded-oversight-5161@gregkh> <20241205083848.GD7451@google.com> <2024120517-bright-expire-955e@gregkh> <20241205092706.GG7451@google.com> 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: <20241205092706.GG7451@google.com> On Thu, Dec 05, 2024 at 09:27:06AM +0000, Lee Jones wrote: > On Thu, 05 Dec 2024, Greg KH wrote: > > > On Thu, Dec 05, 2024 at 08:38:48AM +0000, Lee Jones wrote: > > > On Wed, 04 Dec 2024, Greg KH wrote: > > > > > > > On Wed, Dec 04, 2024 at 05:46:25PM +0000, Lee Jones wrote: > > > > > Expand the complexity of the sample driver by providing the ability to > > > > > get and set an integer. The value is protected by a mutex. > > > > > > > > > > Here is a simple userspace program that fully exercises the sample > > > > > driver's capabilities. > > > > > > > > > > int main() { > > > > > int value, new_value; > > > > > int fd, ret; > > > > > > > > > > // Open the device file > > > > > printf("Opening /dev/rust-misc-device for reading and writing\n"); > > > > > fd = open("/dev/rust-misc-device", O_RDWR); > > > > > if (fd < 0) { > > > > > perror("open"); > > > > > return errno; > > > > > } > > > > > > > > > > // Make call into driver to say "hello" > > > > > printf("Calling Hello\n"); > > > > > ret = ioctl(fd, RUST_MISC_DEV_HELLO, NULL); > > > > > if (ret < 0) { > > > > > perror("ioctl: Failed to call into Hello"); > > > > > close(fd); > > > > > return errno; > > > > > } > > > > > > > > > > // Get initial value > > > > > printf("Fetching initial value\n"); > > > > > ret = ioctl(fd, RUST_MISC_DEV_GET_VALUE, &value); > > > > > if (ret < 0) { > > > > > perror("ioctl: Failed to fetch the initial value"); > > > > > close(fd); > > > > > return errno; > > > > > } > > > > > > > > > > value++; > > > > > > > > > > // Set value to something different > > > > > printf("Submitting new value (%d)\n", value); > > > > > ret = ioctl(fd, RUST_MISC_DEV_SET_VALUE, &value); > > > > > if (ret < 0) { > > > > > perror("ioctl: Failed to submit new value"); > > > > > close(fd); > > > > > return errno; > > > > > } > > > > > > > > > > // Ensure new value was applied > > > > > printf("Fetching new value\n"); > > > > > ret = ioctl(fd, RUST_MISC_DEV_GET_VALUE, &new_value); > > > > > if (ret < 0) { > > > > > perror("ioctl: Failed to fetch the new value"); > > > > > close(fd); > > > > > return errno; > > > > > } > > > > > > > > > > if (value != new_value) { > > > > > printf("Failed: Committed and retrieved values are different (%d - %d)\n", value, new_value); > > > > > close(fd); > > > > > return -1; > > > > > } > > > > > > > > > > // Call the unsuccessful ioctl > > > > > printf("Attempting to call in to an non-existent IOCTL\n"); > > > > > ret = ioctl(fd, RUST_MISC_DEV_FAIL, NULL); > > > > > if (ret < 0) { > > > > > perror("ioctl: Succeeded to fail - this was expected"); > > > > > } else { > > > > > printf("ioctl: Failed to fail\n"); > > > > > close(fd); > > > > > return -1; > > > > > } > > > > > > > > > > // Close the device file > > > > > printf("Closing /dev/rust-misc-device\n"); > > > > > close(fd); > > > > > > > > > > printf("Success\n"); > > > > > return 0; > > > > > } > > > > > > > > > > Signed-off-by: Lee Jones > > > > > --- > > > > > samples/rust/rust_misc_device.rs | 82 ++++++++++++++++++++++++-------- > > > > > 1 file changed, 62 insertions(+), 20 deletions(-) > > > > > > > > > > diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs > > > > > index 5f1b69569ef7..9c041497d881 100644 > > > > > --- a/samples/rust/rust_misc_device.rs > > > > > +++ b/samples/rust/rust_misc_device.rs > > > > > @@ -2,13 +2,20 @@ > > > > > > > > > > //! Rust misc device sample. > > > > > > > > > > +use core::pin::Pin; > > > > > + > > > > > use kernel::{ > > > > > c_str, > > > > > - ioctl::_IO, > > > > > + ioctl::{_IO, _IOC_SIZE, _IOR, _IOW}, > > > > > miscdevice::{MiscDevice, MiscDeviceOptions, MiscDeviceRegistration}, > > > > > + new_mutex, > > > > > prelude::*, > > > > > + sync::Mutex, > > > > > + uaccess::{UserSlice, UserSliceReader, UserSliceWriter}, > > > > > }; > > > > > > > > > > +const RUST_MISC_DEV_GET_VALUE: u32 = _IOR::('R' as u32, 7); > > > > > +const RUST_MISC_DEV_SET_VALUE: u32 = _IOW::('R' as u32, 8); > > > > > > > > Shouldn't this be 'W'? > > > > > > No, I don't think so. > > > > > > 'W' doesn't mean 'write'. It's supposed to be a unique identifier: > > > > > > 'W' 00-1F linux/watchdog.h conflict! > > > 'W' 00-1F linux/wanrouter.h conflict! (pre 3.9) > > > 'W' 00-3F sound/asound.h conflict! > > > 'W' 40-5F drivers/pci/switch/switchtec.c > > > 'W' 60-61 linux/watch_queue.h > > > > > > 'R' isn't registered for this either: > > > > > > 'R' 00-1F linux/random.h conflict! > > > 'R' 01 linux/rfkill.h conflict! > > > 'R' 20-2F linux/trace_mmap.h > > > 'R' C0-DF net/bluetooth/rfcomm.h > > > 'R' E0 uapi/linux/fsl_mc.h > > > > > > ... but since this is just example code with no real purpose, I'm going > > > to hold short of registering a unique identifier for it. > > > > Ah, sorry, I missed that this is the ioctl "name". As the ptrace people > > will complain, why not use a new one? Ick, ioctl-number.rst is way out > > of date, but I guess we should carve out one for "sample drivers, do not > > use in anything real" use cases like here. > > I can carve one out for Samples. > > > > > > + fn get_value(&self, mut writer: UserSliceWriter) -> Result { > > > > > + let guard = self.inner.lock(); > > > > > + > > > > > + pr_info!("-> Copying data to userspace (value: {})\n", &guard.value); > > > > > + > > > > > + writer.write::(&guard.value)?; > > > > > > > > What happens if it fails, shouldn't your pr_info() happen after this? > > > > > > If this fails, I need the line in the log to show where it failed. > > > > pr_info() doesn't show file lines from what I remember has that changed? > > > > But wait, this is a misc device, you should be using dev_info() and > > friends here, no pr_*() stuff please. > > Looks like no other Rust driver does this, so I would be the first. Yes, because those macros just got added this release cycle :) Also, moving the existing in-tree drivers to use these macros would be a good idea. > I need to figure out how to obtain Device data via these APIs. You should have access to it from the misc device structure. > Can I put it on the subsequent work priority list _before_ read/write? It should be in patch 1 :) > > > It says "copying" as in "attempting to copy", rather than "copied". > > > > Fair enough, but if the copy fails, nothing gets printed out, right? > > Not from the kernel, but userspace catches it without issue: > > ioctl: Failed to submit new value: Bad address > > This does not appear to be common practice in kernel Rust. > > The commonly used ? operator seems to just propagate. Ok, nice! automatic error handling is going to be one of the killer features here. greg k-h