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Thu, 2 May 2024 07:46:01 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap1.dmz-prg2.suse.org with ESMTPSA id hL2KJLlEM2biUwAAD6G6ig (envelope-from ); Thu, 02 May 2024 07:46:01 +0000 Date: Thu, 02 May 2024 09:46:14 +0200 Message-ID: <87sez0k661.wl-tiwai@suse.de> From: Takashi Iwai To: Mark Brown Cc: Mauro Carvalho Chehab , Sebastian Fricke , Shengjiu Wang , hverkuil@xs4all.nl, sakari.ailus@iki.fi, tfiga@chromium.org, m.szyprowski@samsung.com, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, shengjiu.wang@gmail.com, Xiubo.Lee@gmail.com, festevam@gmail.com, nicoleotsuka@gmail.com, lgirdwood@gmail.com, perex@perex.cz, tiwai@suse.com, alsa-devel@alsa-project.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v15 00/16] Add audio support in v4l2 framework In-Reply-To: References: <1710834674-3285-1-git-send-email-shengjiu.wang@nxp.com> <20240430082112.jrovosb6lgblgpfg@basti-XPS-13-9310> <20240430172752.20ffcd56@sal.lan> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Spam-Flag: NO X-Spam-Score: -2.01 X-Rspamd-Action: no action X-Rspamd-Queue-Id: 1B2CD1FBAF X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-2.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TAGGED_RCPT(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_TWELVE(0.00)[19]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com,xs4all.nl]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[kernel.org,collabora.com,nxp.com,xs4all.nl,iki.fi,chromium.org,samsung.com,vger.kernel.org,gmail.com,perex.cz,suse.com,alsa-project.org,lists.ozlabs.org]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim]; RCVD_COUNT_TWO(0.00)[2]; DKIM_TRACE(0.00)[suse.de:+] On Wed, 01 May 2024 03:56:15 +0200, Mark Brown wrote: > > On Tue, Apr 30, 2024 at 05:27:52PM +0100, Mauro Carvalho Chehab wrote: > > Mark Brown escreveu: > > > On Tue, Apr 30, 2024 at 10:21:12AM +0200, Sebastian Fricke wrote: > > > > The discussion around this originally was that all the audio APIs are > > > very much centered around real time operations rather than completely > > > The media subsystem is also centered around real time. Without real > > time, you can't have a decent video conference system. Having > > mem2mem transfers actually help reducing real time delays, as it > > avoids extra latency due to CPU congestion and/or data transfers > > from/to userspace. > > Real time means strongly tied to wall clock times rather than fast - the > issue was that all the ALSA APIs are based around pushing data through > the system based on a clock. > > > > That doesn't sound like an immediate solution to maintainer overload > > > issues... if something like this is going to happen the DRM solution > > > does seem more general but I'm not sure the amount of stop energy is > > > proportionate. > > > I don't think maintainer overload is the issue here. The main > > point is to avoid a fork at the audio uAPI, plus the burden > > of re-inventing the wheel with new codes for audio formats, > > new documentation for them, etc. > > I thought that discussion had been had already at one of the earlier > versions? TBH I've not really been paying attention to this since the > very early versions where I raised some similar "why is this in media" > points and I thought everyone had decided that this did actually make > sense. Yeah, it was discussed in v1 and v2 threads, e.g. https://patchwork.kernel.org/project/linux-media/cover/1690265540-25999-1-git-send-email-shengjiu.wang@nxp.com/#25485573 My argument at that time was how the operation would be, and the point was that it'd be a "batch-like" operation via M2M without any timing control. It'd be a very special usage for for ALSA, and if any, it'd be hwdep -- that is a very hardware-specific API implementation -- or try compress-offload API, which looks dubious. OTOH, the argument was that there is already a framework for M2M in media API and that also fits for the batch-like operation, too. So was the thread evolved until now. thanks, Takashi