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 8C6B43164B0; Thu, 16 Oct 2025 11:24:15 +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=1760613855; cv=none; b=LLAjnZd2yj5QWqEpW20wZEZ94kksyCl4ZqMvVfADwsbVyRNaRcLGVgSjdmA4YUPrMyZqgAnZ70mtAXfH9ofCqYRyJf8oTcsrpPg5Jisz0S2gM1/BUrmwdVzuOe84BUTZkJr5e8h/64FGKhbXouyh8dSD82ckkKqkpozZ5CfNtLw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760613855; c=relaxed/simple; bh=0bHQoUy2ApllpsdZzdPazW2pJSX7I7p81GYZ3kyAd0k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rh1f7f2LzHvl0EdmXdPfgAmkLGVetJoUdjSGJOn1RJOFawD35UUplD9k6eXTEGbNSW6X3aHLDb4r/88mMrmujUA7rqd5wm4mRLVEaNuZf6/V9kPScbDCXlAYhL7si+DzdxtJ/UBAgfu68l1G07aDVzmZ4667yWAyKU3GjHA9sTs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=v2tuFb3w; 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="v2tuFb3w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7FAF4C4CEF1; Thu, 16 Oct 2025 11:24:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760613855; bh=0bHQoUy2ApllpsdZzdPazW2pJSX7I7p81GYZ3kyAd0k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=v2tuFb3wo3hjC4GT6QT5kqPgB6bGYyQvgR1FkkPoc3l/HK7MEuKqhxwX908cDG1SE tbQtmPdl+hMEGTjW9G8MsDHQBgOdK51A4lCByHb2H09kbIEK6HnNdf0glTNODQa5X2 hW0z103OSPya/i3cmqIxir/nKZ/YGpo+IG/9vK4M= Date: Thu, 16 Oct 2025 13:24:12 +0200 From: Greg KH To: Ryosuke Yasuoka Cc: arnd@arndb.de, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH rust-next v2 0/3] rust: miscdevice: add llseek support Message-ID: <2025101610-detention-dangle-cef6@gregkh> References: <20251015040246.151141-1-ryasuoka@redhat.com> <2025101544-stopper-rifling-00e0@gregkh> Precedence: bulk X-Mailing-List: linux-fsdevel@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 Thu, Oct 16, 2025 at 07:19:51PM +0900, Ryosuke Yasuoka wrote: > On Wed, Oct 15, 2025 at 07:40:12AM +0200, Greg KH wrote: > > On Wed, Oct 15, 2025 at 01:02:40PM +0900, Ryosuke Yasuoka wrote: > > > Hi all, > > > > > > This patch series add support for the llseek file operation to misc > > > devices written in Rust. > > > > Cool, but what miscdevice driver needs llseek support? Do you have a > > real user for this that we can see as well? > > Currently no. Because lseek is one of fundamental functions for device > driver, I think it's valuable to add support. I believe we'll have real > users based on read, write, and this lseek support. Char devices that use lseek are "odd", don't you agree? There are no such current users under drivers/misc/ and only a rare few under drivers/char/ (the huge user of that is mem.c but we aren't going to be reimplementing that in rust any time soon...) So without a real user of this api, I suggest we hold-off on adding it. Let's not add it until someone comes up with a very valid reason for it. thanks, greg k-h