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,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,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 3FF96C433DF for ; Thu, 20 Aug 2020 04:44:49 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (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 B96C420786 for ; Thu, 20 Aug 2020 04:44:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="stHI9DLv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B96C420786 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 1F63E1677; Thu, 20 Aug 2020 06:43:57 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 1F63E1677 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1597898687; bh=DYFNEahJ3bPqhkhK1wL47kRwrWGAXmyTirAgnDYThRQ=; h=Date:From:To:Subject:References:In-Reply-To:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=stHI9DLvbAeE4zlC0dU7PlO+43EuWZ8tPWvFVfKFxOmRtOYcMpE2HOJQACGyvqZXh q/VMZEw8noM6WKBgWRkPYTmgMwZmljNjY72yEi1+F5oQ8vXY12wlw57K1qJsqZdWIK GnWHRQH8k5aKoFS1N+vkY6xQ1QemK6R3JhZT1gmw= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id 884C4F801F9; Thu, 20 Aug 2020 06:43:56 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id CF2B2F80228; Thu, 20 Aug 2020 06:43:53 +0200 (CEST) Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 2AA8AF80114 for ; Thu, 20 Aug 2020 06:43:49 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 2AA8AF80114 Received: by verein.lst.de (Postfix, from userid 2407) id 5BE8868BEB; Thu, 20 Aug 2020 06:43:47 +0200 (CEST) Date: Thu, 20 Aug 2020 06:43:47 +0200 From: Christoph Hellwig To: Tomasz Figa Subject: Re: [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT Message-ID: <20200820044347.GA4533@lst.de> References: <20200819065555.1802761-1-hch@lst.de> <20200819065555.1802761-6-hch@lst.de> <20200819135454.GA17098@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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-mips@vger.kernel.org, "James E.J. Bottomley" , linux-mm@kvack.org, Christoph Hellwig , Marek Szyprowski , linux-samsung-soc , Joonyoung Shim , linux-scsi@vger.kernel.org, Kyungmin Park , 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 Kernel Mailing List , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" 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. > Also, it of course might be disputable as an out-of-tree usage, but > selecting CONFIG_DMA_NONCOHERENT_CACHE_SYNC makes the flag actually do > something on other platforms, including ARM64. It isn't just disputable, but by kernel policies simply is not relevant.