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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 9A0CEC433E3 for ; Thu, 20 Aug 2020 05:20:13 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 73B1020786 for ; Thu, 20 Aug 2020 05:20:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 73B1020786 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 3019187D5F; Thu, 20 Aug 2020 05:20:13 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id g5kPZy68qUuo; Thu, 20 Aug 2020 05:20:10 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id 9DF7587D51; Thu, 20 Aug 2020 05:20:10 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 80916C07FF; Thu, 20 Aug 2020 05:20:10 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 6A1CEC0051 for ; Thu, 20 Aug 2020 05:20:09 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 41DC1204A6 for ; Thu, 20 Aug 2020 05:20:09 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id P3uoWqVDpXMN for ; Thu, 20 Aug 2020 05:20:08 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by silver.osuosl.org (Postfix) with ESMTPS id 475D5203AC for ; Thu, 20 Aug 2020 05:20:08 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 4B4A168BEB; Thu, 20 Aug 2020 07:20:04 +0200 (CEST) Date: Thu, 20 Aug 2020 07:20:04 +0200 From: Christoph Hellwig To: Tomasz Figa Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT Message-ID: <20200820052004.GA5305@lst.de> References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> <20200820044347.GA4533@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200820044347.GA4533@lst.de> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: alsa-devel@alsa-project.org, linux-ia64@vger.kernel.org, Linux Doc Mailing List , nouveau@lists.freedesktop.org, linux-nvme@lists.infradead.org, Linux Kernel Mailing List , "James E.J. Bottomley" , linux-mm@kvack.org, Christoph Hellwig , linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Ben Skeggs , Matt Porter , Linux Media Mailing List , Tom Lendacky , Pawel Osciak , Mauro Carvalho Chehab , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, Kyungmin Park X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Thu, Aug 20, 2020 at 06:43:47AM +0200, Christoph Hellwig wrote: > On Wed, Aug 19, 2020 at 03:57:53PM +0200, Tomasz Figa wrote: > > > > Could you explain what makes you think it's unused? It's a feature of > > > > the UAPI generally supported by the videobuf2 framework and relied on > > > > by Chromium OS to get any kind of reasonable performance when > > > > accessing V4L2 buffers in the userspace. > > > > > > Because it doesn't do anything except on PARISC and non-coherent MIPS, > > > so by definition it isn't used by any of these media drivers. > > > > It's still an UAPI feature, so we can't simply remove the flag, it > > must stay there as a no-op, until the problem is resolved. > > Ok, I'll switch to just ignoring it for the next version. So I took a deeper look. I don't really think it qualifies as a UAPI in our traditional sense. For one it only appeared in 5.9-rc1, so we can trivially expedite the patch into 5.9-rc and not actually make it show up in any released kernel version. And even as of the current Linus' tree the only user is a test driver. So I really think the best way to go ahead is to just revert it ASAP as the design wasn't thought out at all. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu