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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E1FBC433E0 for ; Wed, 10 Feb 2021 11:32:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD72864E2F for ; Wed, 10 Feb 2021 11:32:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229475AbhBJLbq convert rfc822-to-8bit (ORCPT ); Wed, 10 Feb 2021 06:31:46 -0500 Received: from lithops.sigma-star.at ([195.201.40.130]:59474 "EHLO lithops.sigma-star.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230348AbhBJLYj (ORCPT ); Wed, 10 Feb 2021 06:24:39 -0500 Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 9C6FF6083270; Wed, 10 Feb 2021 12:23:54 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id KtIL8SOfiiUt; Wed, 10 Feb 2021 12:23:54 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 42FF06083272; Wed, 10 Feb 2021 12:23:54 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id CXmfs8niWTKH; Wed, 10 Feb 2021 12:23:54 +0100 (CET) Received: from lithops.sigma-star.at (lithops.sigma-star.at [195.201.40.130]) by lithops.sigma-star.at (Postfix) with ESMTP id 1BDFA6083270; Wed, 10 Feb 2021 12:23:54 +0100 (CET) Date: Wed, 10 Feb 2021 12:23:53 +0100 (CET) From: Richard Weinberger To: Miquel Raynal Cc: Miklos Szeredi , Vignesh Raghavendra , Boris Brezillon , Ron Minnich , sven , linux-kernel , linux-mtd , fuse-devel Message-ID: <1183985773.380599.1612956233979.JavaMail.zimbra@nod.at> In-Reply-To: <20210210121429.4fb5ecf3@xps13> References: <20210124232007.21639-1-richard@nod.at> <1507208626.379155.1612906761549.JavaMail.zimbra@nod.at> <20210210121429.4fb5ecf3@xps13> Subject: Re: [PATCH 0/8] MUSE: Userspace backed MTD v3 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Originating-IP: [195.201.40.130] X-Mailer: Zimbra 8.8.12_GA_3807 (ZimbraWebClient - FF78 (Linux)/8.8.12_GA_3809) Thread-Topic: MUSE: Userspace backed MTD v3 Thread-Index: +AWqGsxtpMS2g3tZtveYZHMCEixznQ== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Miquel, ----- Ursprüngliche Mail ----- >> Does in-band and OOB data need to be handled together? > > Short answer: yes. > >> If so, then two requests is not a good option. > > More detailed answer: > > There is a type of MTD device (NAND devices) which are composed, for > each page, of X in-band bytes plus Y out-of-band metadata bytes. > > Accessing either the in-band data, or the out-of-band data, or both at > the same time are all valid use cases. > > * Read operation details: > From a hardware point of view, the out-of-band data is (almost) > always retrieved when the in-band data is read because it contains > meta-data used to correct eventual bitflips. In this case, if both > areas are requested, it is highly non-efficient to do two requests, > that's why the MTD core allows to do both at the same time. > * Write operation details: > Even worse, in the write case, you *must* write both at the same > time. It is physically impossible to do one after the other (still > with actual hardware, of course). > > That is why it is preferable that MUSE will be able to access both in > a single request. By single request we meant FUSE op-codes. The NAND simulator in Userspace will see just one call. My plan is to abstract it in libfuse. Thanks, //richard