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 62F1B345CD0; Tue, 18 Nov 2025 11:22:01 +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=1763464921; cv=none; b=nYcdWVAOKvwz1SHNsLDc+rqAAuCjdlLXaRMm/+YrKLrRlkDobHxcBUnHin9JZFbmJ9mujr7bXEoBNrFUr2/M7Pk7YqaWmZl/hZlOONDT/nZ8SAqrUnNkjgOakJNqgAJsK7/8EuvJz0fdMyLv8ELEEN2s8rFDCgIb3t0k2BBX4Ho= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763464921; c=relaxed/simple; bh=OSqrTzVKPfEphWSOWozqjN2DP6jQ1KyGCt3LKIzrAwA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nKuflkr3uMeHWXmjsjte6c11WP/XEWppW4d9JkGKJReZquBjrwc9eFAARyu5XxKif2/YPP3uaIGfTShJf+TJ4m/9ffMjhQd/IK57XLsqzNmyDuOt4aDTrUjVCM6baXAOnDW07O3OAuM1mzptn7W4O/k3/aRNc4Yd9oGmQIaZwIQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PiVE8uzM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PiVE8uzM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD7B3C19423; Tue, 18 Nov 2025 11:21:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763464920; bh=OSqrTzVKPfEphWSOWozqjN2DP6jQ1KyGCt3LKIzrAwA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PiVE8uzMlUpbGMOt63k6vT8hw2abfpbdQAia0dP8s95gP0HGX5fqQBVw6T71VApzj KxmYgAGG71dqGOdUg4HjnG6IuQfg5PpRaH9zD70xx5QpJ7SyM66AJNLOx41zAmQA76 Se7qyl+Bj42AlkZ9gFU1Kz+G0qbs1PPVvgf6TZpliCSjdo57yFzup0baGiLn44pKgD ovt78WFggNj7PnxWuPJy7GVjcsYBZ9hWBPefxqqiLlACZYHUOKyU51ZYZ1hV8/c5am LqW7CgaFMV4iZ3wVEipl+0eGPKrwlgcDDl07AGZJpMGkGhJL2ogQFrtaNtLOsITVkS VYdo9nZgRP7GA== Date: Tue, 18 Nov 2025 13:21:34 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, ptyadav@amazon.de, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, jgg@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com, hughd@google.com, skhawaja@google.com, chrisl@kernel.org Subject: Re: [PATCH v6 02/20] liveupdate: luo_core: integrate with KHO Message-ID: References: <20251115233409.768044-1-pasha.tatashin@soleen.com> <20251115233409.768044-3-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-api@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 Mon, Nov 17, 2025 at 11:22:54PM -0500, Pasha Tatashin wrote: > > You can avoid that complexity if you register the device with a different > > fops, but that's technicality. > > > > Your point about treating the incoming FDT as an underlying resource that > > failed to initialize makes sense, but nevertheless userspace needs a > > reliable way to detect it and parsing dmesg is not something we should rely > > on. > > I see two solutions: > > 1. LUO fails to retrieve the preserved data, the user gets informed by > not finding /dev/liveupdate, and studying the dmesg for what has > happened (in reality in fleets version mismatches should not be > happening, those should be detected in quals). > 2. Create a zombie device to return some errno on open, and still > study dmesg to understand what really happened. User should not study dmesg. We need another solution. What's wrong with e.g. ioctl()? > I think that 1 is better > > Pasha -- Sincerely yours, Mike.