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=-0.8 required=3.0 tests=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 5D781C31E40 for ; Sat, 3 Aug 2019 11:22:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D0972075C for ; Sat, 3 Aug 2019 11:22:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389768AbfHCLWJ (ORCPT ); Sat, 3 Aug 2019 07:22:09 -0400 Received: from mx2.suse.de ([195.135.220.15]:38084 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389690AbfHCLWI (ORCPT ); Sat, 3 Aug 2019 07:22:08 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id BF9CCAD3B; Sat, 3 Aug 2019 11:22:06 +0000 (UTC) Date: Sat, 03 Aug 2019 13:22:09 +0200 Message-ID: From: Takashi Iwai To: Christoph Hellwig Cc: iommu@lists.linux-foundation.org, Marek Szyprowski , linux-xtensa@linux-xtensa.org, Michal Simek , linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, Robin Murphy , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 5/5] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP In-Reply-To: <20190803103024.GA32624@lst.de> References: <20190725063401.29904-1-hch@lst.de> <20190725063401.29904-6-hch@lst.de> <20190802070354.GA8280@lst.de> <20190803103024.GA32624@lst.de> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 03 Aug 2019 12:30:24 +0200, Christoph Hellwig wrote: > > On Fri, Aug 02, 2019 at 10:24:02AM +0200, Takashi Iwai wrote: > > I wasn't careful enough to look at that change, sorry. > > > > The code there tries to check whether dma_mmap_coherent() would always > > fail on some platforms. Then the driver clears the mmap capability > > flag at the device open time and notifies user-space to fall back to > > the dumb read/write mode. > > > > So I'm afraid that simply dropping the check would cause the behavior > > regression, e.g. on PARISC. > > > > Is there any simple way to test whether dma_mmap_coherent() would work > > or not in general on the target platform? It's not necessarily in an > > ifdef at all. > > This isn't really a platform, but a per-device question. I can add a > "bool dma_can_mmap(struct device *dev)" helper to check that. Yes, this would fit perfect. > But how > do I get at a suitable struct device in hw_support_mmap()? substream->dma_buffer.dev.dev can be that, which is used in the mmap helper side, snd_pcm_lib_default_mmap(). Thanks! Takashi