From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre-Louis Bossart Subject: Re: [alsa-devel] [PATCH v2 3/5] ASoC: core: add support to snd_soc_dai_get_sdw_stream() Date: Wed, 9 Oct 2019 13:53:51 -0500 Message-ID: <2326a155-332e-fda0-b7a2-b48f348e1911@linux.intel.com> References: <20190813083550.5877-1-srinivas.kandagatla@linaro.org> <20190813083550.5877-4-srinivas.kandagatla@linaro.org> <20190813191827.GI5093@sirena.co.uk> <20190813195804.GL5093@sirena.co.uk> <20190814041142.GU12733@vkoul-mobl.Dlink> <99d35a9d-cbd8-f0da-4701-92ef650afe5a@linux.intel.com> <5e08f822-3507-6c69-5d83-4ce2a9f5c04f@linaro.org> <53bb3105-8e85-a972-fce8-a7911ae4d461@linux.intel.com> <95870089-25da-11ea-19fd-0504daa98994@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <95870089-25da-11ea-19fd-0504daa98994@linaro.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Srinivas Kandagatla , Vinod Koul , Mark Brown Cc: devicetree@vger.kernel.org, alsa-devel@alsa-project.org, bgoswami@codeaurora.org, plai@codeaurora.org, linux-kernel@vger.kernel.org, lgirdwood@gmail.com, robh+dt@kernel.org, spapothi@codeaurora.org List-Id: devicetree@vger.kernel.org On 10/9/19 11:01 AM, Srinivas Kandagatla wrote: > > > On 09/10/2019 15:29, Pierre-Louis Bossart wrote: >> >> >> On 10/9/19 3:32 AM, Srinivas Kandagatla wrote: >>> Hi Pierre, >>> >>> On 14/08/2019 15:09, Pierre-Louis Bossart wrote: >>>> >>>> >>>> On 8/13/19 11:11 PM, Vinod Koul wrote: >>>>> On 13-08-19, 20:58, Mark Brown wrote: >>>>>> On Tue, Aug 13, 2019 at 02:38:53PM -0500, Pierre-Louis Bossart wrote: >>>>>> >>>>>>> Indeed. I don't have a full understanding of that part to be >>>>>>> honest, nor why >>>>>>> we need something SoundWire-specific. We already abused the >>>>>>> set_tdm_slot API >>>>>>> to store an HDaudio stream, now we have a rather confusing stream >>>>>>> information for SoundWire and I have about 3 other 'stream' >>>>>>> contexts in >>>>>>> SOF... I am still doing basic cleanups but this has been on my >>>>>>> radar for a >>>>>>> while. >>>>>> >>>>>> There is something to be said for not abusing the TDM slot API if >>>>>> it can >>>>>> make things clearer by using bus-idiomatic mechanisms, but it does >>>>>> mean >>>>>> everything needs to know about each individual bus :/ . >>>>> >>>>> Here ASoC doesn't need to know about sdw bus. As Srini explained, this >>>>> helps in the case for him to get the stream context and set the stream >>>>> context from the machine driver. >>>>> >>>>> Nothing else is expected to be done from this API. We already do a set >>>>> using snd_soc_dai_set_sdw_stream(). Here we add the >>>>> snd_soc_dai_get_sdw_stream() to query >>>> >>>> I didn't see a call to snd_soc_dai_set_sdw_stream() in Srini's code? >>> >>> >>> There is a snd_soc_dai_get_sdw_stream() to get stream context and we >>> add slave streams(amplifier in this case) to that context using >>> sdw_stream_add_slave() in machine driver[1]. >>> >>> Without this helper there is no way to link slave streams to stream >>> context in non dai based setup like smart speaker amplifiers. >>> >>> Currently this driver is blocked on this patch, If you think there >>> are other ways to do this, am happy to try them out. >> >> So to be clear, you are *not* using snd_soc_dai_set_sdw_stream? > Yes, am not using snd_soc_dai_set_sdw_stream(). It's been a while since this thread started, and I still don't quite get the concepts or logic. First, I don't understand what the problem with "aux" devices is. All the SoundWire stuff is based on the concept of DAI, so I guess I am missing why introducing the "aux" device changes anything. Next, a 'stream' connects multiple DAIs to transmit information from sources to sinks. A DAI in itself is created without having any notion of which stream it will be associated with. This can only be done with machine level information. If you query a DAI to get a stream context, then how is this stream context allocated in the first place? It looks like a horse and cart problem. Or you are assuming that a specific DAI provides the context, and that all other DAIs do not expose this .get_sdw_stream()? What if more that 1 DAI provide a stream context? And last, I am even more lost since w/ the existing codec drivers we have, sdw_stream_add_slave() is called from the dai .hw_params callback, once you have information on formats/rates, etc. using sdw_stream_add_slave() from a machine driver looks like an even bigger stretch. I really thought the machine driver would only propagate the notion of stream to all DAIs that are part of the same dailink. I am not trying to block the Qualcomm implementation, just would like to make sure the assumptions are clear and that we are not using the same API in completely different ways.