From: Pierre-Louis Bossart <email@example.com> To: "Lu, Brent" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org> Cc: "Rojewski, Cezary" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, Ranjani Sridharan <firstname.lastname@example.org> Subject: Re: [alsa-devel] [PATCH] ASoC: bdw-rt5677: channel constraint support Date: Thu, 12 Sep 2019 08:06:35 -0500 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <CF33C36214C39B4496568E5578BE70C7402DBB9B@PGSMSX108.gar.corp.intel.com> On 9/12/19 1:00 AM, Lu, Brent wrote: >>> >>> The story is Chrome has a tool called alsa_conformance_test which runs >>> capture or playback against a PCM port with all possible >>> configurations (channel, format, rate) then measure if the sample rate >>> is correct. Since the channel max number reported is 4, it tests the >>> 4-channel 48K capture and reports the actual sample rate is 24000 >>> instead of 48000. That's the reason we want to add a constraint in >>> machine driver to avoid user space programs trying to do 4 channel >> recording since this machine does not support it in the beginning. >> >> ok, that helps get context, thanks for the details. >> >> I would have expected some error to be returned if there's a front-end >> opened with 4 channels and the back-end only supports two. Adding the >> constraint seems like a work-around to avoid dealing with the mismatch >> between FE and BE. I don't understand DPCM enough to suggest an >> alternative though. Ranjani, can you help on this one? >> >> And even if we agree with this solution, it'd be nice to apply it for the >> Broadwell machine driver for consistency. > > It's not only the mismatch but also the design limitation. According to the > information from google, the board (samus) only uses two microphone so > 3 or 4 channel recording are not supported. That's the reason we leverage > the constraint from other machine driver (like kbl_da7219_max98357a.c) > to remove the 3 and 4 channel recording option. The design limitation is already handled by the fact that the SSP operates in 2ch mode, so it's a different case from KBL where indeed the DMIC-based back-end can support 4 channels. > > The difference after the constraint is implemented is that the > snd_pcm_hw_params_set_channels() function will return error (Invalid > argument) when channel number is 3 or 4 so the application knows the > configuration is not supported. I get the error, I am just wondering if the fix is at the right location. I'll look into it, give me until tomorrow.
next prev parent reply other threads:[~2019-09-12 13:06 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-09-06 1:24 Brent Lu 2019-09-06 14:20 ` [alsa-devel] " Pierre-Louis Bossart 2019-09-09 6:34 ` Lu, Brent 2019-09-09 17:53 ` Pierre-Louis Bossart 2019-09-10 8:28 ` Lu, Brent 2019-09-10 14:12 ` Pierre-Louis Bossart 2019-09-12 6:00 ` Lu, Brent 2019-09-12 13:06 ` Pierre-Louis Bossart [this message] 2019-09-27 12:34 ` Lu, Brent
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --subject='Re: [alsa-devel] [PATCH] ASoC: bdw-rt5677: channel constraint support' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).