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 09B8B58222; Fri, 6 Dec 2024 06:42:53 +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=1733467374; cv=none; b=hhRWeo5/NAgQ+Rah0ndka+1RCGb4nsUu+x4zmYd08Sthss3alAvt6/k9h6QY1lmX7fLKVgF2a0ZIHZzV5Rq4Vi6NZQF35fZ9cSOAfrM7veoC7X27B7Z4LfXYWFMnh7N14+J+F2Co69L0F3lYjkl2Vyov4zsjlDGx5nEAlLrubzI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733467374; c=relaxed/simple; bh=lc2eNUxj94J3so9pJfyH+alTtf29ra0uAXnLKam+tck=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=oxDiVMk240Nbghc9w7QPT6SUvyZ5kvowM7vrQa7e9/KI9ndfwFlxbW+fano9Hq0NhzXKJSqQciTi1avGgTS3vJiEVgHLumNdiX6DbUtcaH7kH5MooqPjk1+j/tZe+Ad01XI2IymZnV3ql1W5wyLYa8uHK1YG76OtnU/ddNh3aPs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QBDHZQYb; 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="QBDHZQYb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2336C4CED1; Fri, 6 Dec 2024 06:42:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1733467373; bh=lc2eNUxj94J3so9pJfyH+alTtf29ra0uAXnLKam+tck=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QBDHZQYbLHrcnuJGPuSUMI2oqAqCCS/Cww6miVgyictF7S4bHUKIQnVGTW1rZz80a axVsxMrIYURovPR8PvMcTe+gksS3wo0OAcJXxHXMq2FXNVDIq2+xmbGTcAcO2NhkUc 1p5VjLk5f1zcNhoUys7vZU+XRQmPT0W0RXR4VPOs= Date: Fri, 6 Dec 2024 07:42:50 +0100 From: Greg KH To: Lee Jones 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 1/5] rust: miscdevice: Provide accessor to pull out miscdevice::this_device Message-ID: <2024120648-finch-shrubbery-c6f5@gregkh> References: <20241205162531.1883859-1-lee@kernel.org> <20241205162531.1883859-2-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: <20241205162531.1883859-2-lee@kernel.org> On Thu, Dec 05, 2024 at 04:25:18PM +0000, Lee Jones wrote: > There are situations where a pointer to a `struct device` will become > necessary (e.g. for calling into dev_*() functions). This accessor > allows callers to pull this out from the `struct miscdevice`. > > Signed-off-by: Lee Jones > --- > rust/kernel/miscdevice.rs | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs > index 7e2a79b3ae26..55340f316006 100644 > --- a/rust/kernel/miscdevice.rs > +++ b/rust/kernel/miscdevice.rs > @@ -10,11 +10,13 @@ > > use crate::{ > bindings, > + device::Device, > error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR}, > prelude::*, > str::CStr, > types::{ForeignOwnable, Opaque}, > }; > + > use core::{ > ffi::{c_int, c_long, c_uint, c_ulong}, > marker::PhantomData, > @@ -84,6 +86,13 @@ pub fn register(opts: MiscDeviceOptions) -> impl PinInit { > pub fn as_raw(&self) -> *mut bindings::miscdevice { > self.inner.get() > } > + > + /// Returns a pointer to the current Device > + pub fn device(&self) -> &Device { > + // SAFETY: This is only accessible after a successful register() which always > + // initialises this_device with a valid device. > + unsafe { Device::as_ref((*self.as_raw()).this_device) } A "raw" pointer that you can do something with without incrementing the reference count of it? Oh wait, no, it's the rust device structure. If so, why isn't this calling the get_device() interface instead? That way it's properly incremented and decremented when it "leaves the scope" right? Or am I missing something here as to why that wouldn't work and this is the only way to get access to the 'struct device' of this miscdevice? thanks, greg k-h