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 C086C1AF4D5; Sat, 14 Mar 2026 11:52:35 +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=1773489155; cv=none; b=NMPJjy/wlC2iazgmQEKuds5MgIfsAuJEILaOlyoPkh9soQCsXfa4nuLgX9V9dJNQB+CGzDOBYXMEW8aFJK9oMnyqk87I3c68MwkCkk7/tPicXgMupInT15ImyyN3TTsmH5Pz6u+hYc1oFDSHrdQyCgVgRyGtlGRV8c7zQx43+oc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773489155; c=relaxed/simple; bh=YtuOZ55W8PDmlGkVLBE4be0lCpswLb+7bbBVz7Kd9Gw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Te6tn57jL5w2+6lW3jDDob9Y+qrWFnEu0KHHgHkNqh3dTaa7debviRvNP3VOwj2cgcv/AoL/ad958qSAy7WmlQciMaev5mq0Pzfy0QDvwGBaZRbLml1DrLMiex0u/xuVzNjs6nFD4QQlWN23ONGKZw1GHGQmyZdvpXdCQho0YPU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=s9+v0ZA6; 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="s9+v0ZA6" 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> Precedence: bulk X-Mailing-List: linux-serial@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: 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