From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 05640AB9 for ; Mon, 26 Jun 2017 12:38:57 +0000 (UTC) Received: from atrey.karlin.mff.cuni.cz (atrey.karlin.mff.cuni.cz [195.113.26.193]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 6491F3CC for ; Mon, 26 Jun 2017 12:38:56 +0000 (UTC) Date: Mon, 26 Jun 2017 14:38:53 +0200 From: Pavel Machek To: Mark Brown Message-ID: <20170626123853.GB11441@amd> References: <20170625104850.GA24717@amd> <20170626105451.tv4k7ib2g2kiknah@sirena.org.uk> <20170626111422.GB11688@amd> <20170626114946.bw35etwxa2nungsi@sirena.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="8GpibOaaTibBMecb" Content-Disposition: inline In-Reply-To: <20170626114946.bw35etwxa2nungsi@sirena.org.uk> Cc: ksummit-discuss@lists.linuxfoundation.org Subject: Re: [Ksummit-discuss] [TECH TOPIC] mobile phones List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --8GpibOaaTibBMecb Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon 2017-06-26 12:49:46, Mark Brown wrote: > On Mon, Jun 26, 2017 at 01:14:22PM +0200, Pavel Machek wrote: >=20 > > > Do you have some more specific concern? This already works basically > > > fine upstream, we happily support off-SoC audio paths. The digital > > > configuration could do with being more flexible but it works and peop= le > > > ship it. It would be awfully nice to have some control/visibility of > > > the modem side but that's just a missing driver problem. >=20 > > Well, I was told gsm audio is different, because it is packetized, has > > additional timing info, and does not transmit silence. >=20 > Those things are true, however this is all handled inside the modem so > nothing else in the system sees anything there. Even if we were to see > things this is pretty much just VoIP over a funny carrier (some of the > 4G standards are just SIP AIUI) which isn't too hard. I'm still asking for one example of system that's properly designed according to you. It may be "VoIP over funny carrier" -- but how do you suggest we handle it? ALSA is for soundcards, not for VoIP so maybe /dev/cmtspeech is okay after all? > > So we have /dev/cmtspeech instead of second sound card. >=20 > That's just whatever random thing you're working on. It really > shouldn't be a second sound card on a well designed system, the phone > audio generally doesn't go anywhere near the CPU for latency reasons so > the whole system is one sound card. First, where can I buy example of such well-designed system? Second, no I can't agree. I certainly don't want baseband CPU to talk directly to my speakers/microphone, for security reasons. Then there's an option to process the sound between sending it over GSM, record calls, etc. I quite like the flexibility, too. Latency problems are solveable in software -- N900 with Maemo has reasonable call quality. Third, I already have the system, I'm asking how to support it cleanly. > > Is there any GSM audio driver that actually uses sound framework > > properly? >=20 > The modems tend to just be stub drivers to Linux as the audio port > doesn't vary configuration at runtime but I'd be a bit surprised if a > modern phone wasn't broadly aiming towards the right thing, this stuff > started appearing in flagship devices in about 2012. The speyside > system in mainline isn't actually a phone but models what's going on. Well, the flagship devices are have 1000000+ lines of diffs relative to mainline, due to Qualcomm, right? :-(. Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --8GpibOaaTibBMecb Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAllRAF0ACgkQMOfwapXb+vKEtgCgkI3d2R+T9AS/mWQhr6Pvttjz ZfkAmwQkCxRCpf5i24ORbg77xi1h81yC =/Bpc -----END PGP SIGNATURE----- --8GpibOaaTibBMecb--