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,DKIM_SIGNED, DKIM_VALID,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 C3210C433E2 for ; Mon, 14 Sep 2020 15:27:51 +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 6A6E120665 for ; Mon, 14 Sep 2020 15:27:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="k3lvLg5w"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="M80c+D3B" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A6E120665 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 2961616AF; Mon, 14 Sep 2020 17:26:57 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 2961616AF DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1600097267; bh=+fuKzsdD6GGAWfgaunNdIsI1FDobsMLAJmSSvG7gzGU=; h=Date:From:To:Subject:References:In-Reply-To:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=k3lvLg5wujKZoTZyOfB186Z6uxatunbh4B26p+rAsYd5NDF2ZgVSwOBWjGslApZsb cryP+oBvVbKTlFzxIA3Jr32Mr2twQPViHDhwIdoY3wjPuh9wAeQBC2TE17Z1Bkh0Jj XQJ0LRKg4Q+H3L9ijhVYF45TmtENiACA8NzMFe+k= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id AE5A0F80150; Mon, 14 Sep 2020 17:26:56 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 45098F8015A; Mon, 14 Sep 2020 17:26:55 +0200 (CEST) Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id B7047F80105 for ; Mon, 14 Sep 2020 17:26:48 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz B7047F80105 Authentication-Results: alsa1.perex.cz; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="M80c+D3B" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=7O2Rc307Jq8KkaDn7zbVItvtt/ecHc/too3yP9zxMNw=; b=M80c+D3BqJySppi+H3eNYCcnH/ gkfi1LX5tkOxqiYr7vGlDhimfScWmyFoD4H7IZc29yxj59fxiZw4CTf73qE/Frs6kv2D1VP9Z0cDk mxHwC6y23VXZp0GWVeuCJj/TuYsYfRbshYeLxTfn4NkxNbZt/mCYZDG48aAzhZnPSD26Tjx+8/mwu 2BX9yzKsoQKr11uV/Bwnigc9od3UdV8s2rG69+T+l2QU+9l3XPVzWYgBbLqR3TeV+3H8nv+hHYZRQ AbZDHlAxP767K2OWIVLYATsG32mlziFsc93sPs4pmGxH1oa7RFwa/hq19KGZWcLA7yuKXtQ9v35Ul oAwe3FdQ==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kHqN0-0004bK-27; Mon, 14 Sep 2020 15:26:18 +0000 Date: Mon, 14 Sep 2020 16:26:17 +0100 From: Matthew Wilcox To: Christoph Hellwig Subject: Re: a saner API for allocating DMA addressable pages v2 Message-ID: <20200914152617.GR6583@casper.infradead.org> References: <20200914144433.1622958-1-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200914144433.1622958-1-hch@lst.de> Cc: alsa-devel@alsa-project.org, linux-doc@vger.kernel.org, nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org, "James E.J. Bottomley" , linux-mm@kvack.org, linux1394-devel@lists.sourceforge.net, Marek Szyprowski , linux-samsung-soc@vger.kernel.org, Joonyoung Shim , linux-scsi@vger.kernel.org, Ben Skeggs , Matt Porter , linux-media@vger.kernel.org, Mauro Carvalho Chehab , linux-arm-kernel@lists.infradead.org, Thomas Bogendoerfer , linux-parisc@vger.kernel.org, netdev@vger.kernel.org, Seung-Woo Kim , linux-mips@vger.kernel.org, Tomasz Figa , iommu@lists.linux-foundation.org, Stefan Richter 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 Mon, Sep 14, 2020 at 04:44:16PM +0200, Christoph Hellwig wrote: > I'm still a little unsure about the API naming, as alloc_pages sort of > implies a struct page return value, but we return a kernel virtual > address. Erm ... dma_alloc_pages() returns a struct page, so is this sentence stale? >From patch 14: +struct page *dma_alloc_pages(struct device *dev, size_t size, + dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp); > The other alternative would be to name the API > dma_alloc_noncoherent, but the whole non-coherent naming seems to put > people off. You say that like it's a bad thing. I think the problem is more that people don't understand what non-coherent means and think they're supporting it when they're not. dma_alloc_manual_flushing()? > As a follow up I plan to move the implementation of the > DMA_ATTR_NO_KERNEL_MAPPING flag over to this framework as well, given > that is also is a fundamentally non coherent allocation. The replacement > for that flag would then return a struct page, as it is allowed to > actually return pages without a kernel mapping as the name suggested > (although most of the time they will actually have a kernel mapping..) If the page doesn't have a kernel mapping, shouldn't it return a PFN or a phys_addr?