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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55A17CDB47E for ; Wed, 18 Oct 2023 18:07:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232110AbjJRSHh (ORCPT ); Wed, 18 Oct 2023 14:07:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231865AbjJRSHc (ORCPT ); Wed, 18 Oct 2023 14:07:32 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23120113 for ; Wed, 18 Oct 2023 11:07:30 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 6B3B121B6E; Wed, 18 Oct 2023 18:07:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1697652448; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rgWIZctOW4uIbvAqVFAKuzU4R6bejxr6bFDySXRomUs=; b=TKfib127vE0yESnlakrcaG6iYKuFRLAxet2Tw0XvVsK0VF2QIFdEE4w/3pUi7pycvYRzci Y+kO6EJoxJIUve1e2qRayrB04uP5SkBGeSR5wRL2dTOPoav6a69gjY+juqQb8id6GRpPe8 qZNghYKuNBzo1Nzw4UyZ9zC0l/2iqp4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1697652448; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rgWIZctOW4uIbvAqVFAKuzU4R6bejxr6bFDySXRomUs=; b=rPq8p6KgNU5YezSgzvOGtloZv4OA7fVDrfn5rPVv3oklRhlaObEelElPoRQuTzsOGsV6DE 8xUJ9GDw8Qwz1SAg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 1553113915; Wed, 18 Oct 2023 18:07:28 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id kHo/BOAeMGWKRwAAMHmgww (envelope-from ); Wed, 18 Oct 2023 18:07:28 +0000 Date: Wed, 18 Oct 2023 20:07:27 +0200 Message-ID: <871qdrn6sg.wl-tiwai@suse.de> From: Takashi Iwai To: Matias Ezequiel Vara Larsen Cc: anton.yakovlev@opensynergy.com, mst@redhat.com, perex@perex.cz, tiwai@suse.com, virtualization@lists.linux-foundation.org, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, stefanha@redhat.com, sgarzare@redhat.com, manos.pitsidianakis@linaro.org, mripard@redhat.com Subject: Re: [PATCH v2] ALSA: virtio: use copy and fill_silence callbacks In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII Authentication-Results: smtp-out1.suse.de; none X-Spamd-Result: default: False [-10.10 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-3.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; REPLY(-4.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-1.00)[-1.000]; RCPT_COUNT_TWELVE(0.00)[13]; MID_CONTAINS_FROM(1.00)[]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 18 Oct 2023 12:48:23 +0200, Matias Ezequiel Vara Larsen wrote: > > This commit replaces the mmap mechanism with the copy() and > fill_silence() callbacks for both capturing and playback for the > virtio-sound driver. This change is required to prevent the updating of > the content of a buffer that is already in the available ring. > > The current mechanism splits a dma buffer into descriptors that are > exposed to the device. This dma buffer is shared with the user > application. When the device consumes a buffer, the driver moves the > request from the used ring to available ring. > > The driver exposes the buffer to the device without knowing if the > content has been updated from the user. The section 2.8.21.1 of the > virtio spec states that: "The device MAY access the descriptor chains > the driver created and the memory they refer to immediately". If the > device picks up buffers from the available ring just after it is > notified, it happens that the content may be old. > > By providing the copy() callback, the driver first updates the content > of the buffer, and then, exposes the buffer to the device by enqueuing > it in the available ring. Thus, device always picks up a buffer that is > updated. During copy(), the number of requests enqueued depends on the > "pos" and "bytes" arguments. The length of each request is period_size > bytes. > > For capturing, the driver starts by exposing all the available buffers > to device. After device updates the content of a buffer, it enqueues it > in the used ring. It is only after the copy() for capturing is issued > that the driver re-enqueues the buffer in the available ring. > > Co-developed-by: Anton Yakovlev > Signed-off-by: Matias Ezequiel Vara Larsen > --- > Changelog: > v1 -> v2: > * Use snd_pcm_set_managed_buffer_all()for buffer allocation/freeing. > * Make virtsnd_pcm_msg_send() generic by specifying the offset and size > for the modified part of the buffer; this way no assumptions need to > be made. > * Disable SNDRV_PCM_INFO_NO_REWINDS since now only sequential > reading/writing of frames is supported. > * Correct comment at virtsnd_pcm_msg_send(). > * v1 patch at: > https://lore.kernel.org/lkml/20231016151000.GE119987@fedora/t/ > > sound/virtio/virtio_pcm.c | 7 ++- > sound/virtio/virtio_pcm.h | 9 ++-- > sound/virtio/virtio_pcm_msg.c | 93 ++++++++++++++++++++++------------- > sound/virtio/virtio_pcm_ops.c | 81 +++++++++++++++++++++++++----- > 4 files changed, 137 insertions(+), 53 deletions(-) Most of the code changes look good, but I wonder: > > diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c > index c10d91fff2fb..66d67eef1bcc 100644 > --- a/sound/virtio/virtio_pcm.c > +++ b/sound/virtio/virtio_pcm.c > @@ -104,12 +104,11 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, > * only message-based transport. > */ > vss->hw.info = > - SNDRV_PCM_INFO_MMAP | > - SNDRV_PCM_INFO_MMAP_VALID | Do we need the removal of those MMAP features inevitably? Usually mmap can still work even if the driver implements the copy ops. Those aren't always mutual exclusive. thanks, Takashi