From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 821A310706CC for ; Sat, 14 Mar 2026 11:52:38 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B21D010E490; Sat, 14 Mar 2026 11:52:37 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="s9+v0ZA6"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id EF71D10E490 for ; Sat, 14 Mar 2026 11:52:35 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 8249240E24; Sat, 14 Mar 2026 11:52:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82A56C116C6; Sat, 14 Mar 2026 11:52:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1773489155; bh=YtuOZ55W8PDmlGkVLBE4be0lCpswLb+7bbBVz7Kd9Gw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s9+v0ZA6+GWWKYRvJli/W2sGWMVldNwhLNWxqAFjZ5rblzbxzv+HV5KlIdTDLjT8K 3BBzTsWonv56AhpnRF5hqtt4nY58f0l4pzxhxqtBJkTNyuloB6bsl+/t6uqQNbHVRy hrlhYQ0VlW8oXaaO1rEAAiIrimDaIXCWNv0He5JI= Date: Sat, 14 Mar 2026 12:52:31 +0100 From: Greg Kroah-Hartman To: Markus Probst Cc: Rob Herring , Jiri Slaby , Miguel Ojeda , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Kari Argillander , "Rafael J. Wysocki" , Viresh Kumar , Boqun Feng , David Airlie , Simona Vetter , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-pm@vger.kernel.org, driver-core@lists.linux.dev, dri-devel@lists.freedesktop.org Subject: Re: [PATCH v3 2/4] serdev: add rust private data to serdev_device Message-ID: <2026031422-shaded-matchbook-5078@gregkh> References: <20260313-rust_serdev-v3-0-c9a3af214f7f@posteo.de> <20260313-rust_serdev-v3-2-c9a3af214f7f@posteo.de> <2026031402-absence-graph-af5d@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Sat, Mar 14, 2026 at 11:42:02AM +0000, Markus Probst wrote: > On Sat, 2026-03-14 at 09:07 +0100, Greg Kroah-Hartman wrote: > > On Fri, Mar 13, 2026 at 06:12:31PM +0000, Markus Probst wrote: > > > Add rust private data to `struct serdev_device`, as it is required by the > > > rust abstraction added in the following commit > > > (rust: add basic serial device bus abstractions). > > > > why is rust "special" here? What's wrong with the existing private > > pointer in this structure? Why must we add another one? > Because in rust, the device drvdata will be set after probe has run. In > serdev, once the device has been opened, it can receive data. It must > be opened either inside probe or before probe, because it can only be > configured (baudrate, flow control etc.) and data written to after it > has been opened. Because it can receive data before drvdata has been > set yet, we need to ensure it waits on data receival for the probe to > be finished. Otherwise this would be a null pointer dereference. To do > this, we need to store a `Completion` for it to wait and a `bool` in > case the probe exits with an error. We cannot store this data in the > device drvdata, because this is where the drivers drvdata goes. We also > cannot create a wrapper of the drivers drvdata, because > `Device::drvdata::()` would always fail in that case. That is why we > need a "rust_private_data" for this abstraction to store the > `Completion` and `bool`. So why is this any different from any other bus type? I don't see the "uniqueness" here that has not required this to happen for PCI or USB or anything else. What am I missing? Also, all of this information MUST be in the changelog text in order for us to be able to accept it. You need to say _why_ a change is needed, not just _what_ the change does, as you know. thanks, greg k-h