From: "Lu, Brent" <email@example.com> To: Pierre-Louis Bossart <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 06:00:45 +0000 [thread overview] Message-ID: <CF33C36214C39B4496568E5578BE70C7402DBB9B@PGSMSX108.gar.corp.intel.com> (raw) In-Reply-To: <email@example.com> > > > > 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 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. Regards, Brent
next prev parent reply other threads:[~2019-09-12 6:04 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 [this message] 2019-09-12 13:06 ` Pierre-Louis Bossart 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 \ --in-reply-to=CF33C36214C39B4496568E5578BE70C7402DBB9B@PGSMSX108.gar.corp.intel.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 \ --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).