linux-kernel - Re: [PATCH v3 2/3] rust: miscdevice: access the `struct miscdevice` from fops->open()

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Message-ID: <20241213164745.GC2418536@google.com>
Date: Fri, 13 Dec 2024 16:47:45 +0000
From: Lee Jones <lee@...nel.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] rust: miscdevice: access the `struct miscdevice`
 from fops->open()

On Wed, 11 Dec 2024, Lee Jones wrote:

> On Tue, 10 Dec 2024, Alice Ryhl wrote:
> 
> > Providing access to the underlying `struct miscdevice` is useful for
> > various reasons. For example, this allows you access the miscdevice's
> > internal `struct device` for use with the `dev_*` printing macros.
> > 
> > Note that since the underlying `struct miscdevice` could get freed at
> > any point after the fops->open() call (if misc_deregister is called),
> > only the open call is given access to it. To use `dev_*` printing macros
> > from other fops hooks, take a refcount on `miscdevice->this_device` to
> > keep it alive. See the linked thread for further discussion on the
> > lifetime of `struct miscdevice`.
> > 
> > Link: https://lore.kernel.org/r/2024120951-botanist-exhale-4845@gregkh
> > Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> > ---
> >  rust/kernel/miscdevice.rs | 30 ++++++++++++++++++++++--------
> >  1 file changed, 22 insertions(+), 8 deletions(-)
> 
> Reviewed-by: Lee Jones <lee@...nel.org>

Tested-by: Lee Jones <lee@...nel.org>

-- 
Lee Jones [李琼斯]