linux-kernel - Re: [PATCH 0/3] rust: miscdevice: Add additional data to MiscDeviceRegistration

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Message-ID: <41cee8ac-f773-4e7b-8249-2de5d7807287@gmail.com>
Date: Tue, 21 Jan 2025 11:29:40 +0100
From: Christian Schrefl <chrisi.schrefl@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: 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>, Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>, Arnd Bergmann <arnd@...db.de>,
 Lee Jones <lee@...nel.org>, rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] rust: miscdevice: Add additional data to
 MiscDeviceRegistration


On 20.01.25 6:46 AM, Greg Kroah-Hartman wrote:
> On Sun, Jan 19, 2025 at 11:11:12PM +0100, Christian Schrefl wrote:
>> This set is based on Greg's driver-core-next tree.
>>
>> Currently there is no good way to pass arbitrary data from the driver to
>> a miscdevice or to share data between individual handles to a miscdevice in rust.
> 
> Why would you want to do this?  A misc device instance should be "self
> contained" with the needed stuff to make it work.
> 
> Do you have an example of where this is needed as I can't figure out the
> goal here, sorry.

The main reason for needing this was that I could not figure out how to otherwise
use a Devres from the platfrom driver probe in the implementation of the miscdevice.
The reason to add this to MiscDeviceRegistration is to avoid race-conditions between
the fops and driver registration/deregistration.
(See the commit description of patch 2/3)

If there is a better or more intended way to achieve that please let me know.

> 
> thanks,
> 
> greg k-h