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 D57B6279 for ; Fri, 31 Jul 2015 17:52:47 +0000 (UTC) Received: from mezzanine.sirena.org.uk (mezzanine.sirena.org.uk [106.187.55.193]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 544F11C1 for ; Fri, 31 Jul 2015 17:52:47 +0000 (UTC) Date: Fri, 31 Jul 2015 18:52:15 +0100 From: Mark Brown To: Pavel Machek Message-ID: <20150731175215.GJ20873@sirena.org.uk> References: <20150723105726.GC30929@amd> <20150723121441.GB29747@amd> <20150723084251.54da2be0@gandalf.local.home> <20150723202901.GA30318@amd> <20150729133244.GH20130@sirena.org.uk> <20150731122227.GA31877@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="pMCBjikF2xGw87uL" Content-Disposition: inline In-Reply-To: <20150731122227.GA31877@amd> Cc: "ksummit-discuss@lists.linuxfoundation.org" , riverful.kim@samsung.com, kyungmin.park@samsung.com, John Stultz , Bjorn Andersson Subject: Re: [Ksummit-discuss] [CORE TOPIC] Mainline kernel on a cellphone List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --pMCBjikF2xGw87uL Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jul 31, 2015 at 02:22:27PM +0200, Pavel Machek wrote: > On Wed 2015-07-29 14:32:44, Mark Brown wrote: > > On Thu, Jul 23, 2015 at 10:29:02PM +0200, Pavel Machek wrote: > > ALSA is the right interface for this, this is going to be some > > misunderstanding on their part about how to use it or limitations in > That's what I was arguing, but see https://lkml.org/lkml/2015/3/5/606 I can't view that link since lkml.org was down earlier today when I was working online and now I'm working offline. > kai> Our take was that ALSA is not the right interface for cmt_speech. The > kai> cmt_speech interface in the modem is _not_ a PCM interface as modelled > kai> by > kai> ALSA. Specifically: > kai> > kai>- the interface is lossy in both directions Yay. > kai>- data is sent in packets, not a stream of samples (could be other > kai>- things > kai> than PCM samples), with timing and meta-data This is what the copy() operation in the driver is for, there are other DSP based devices out there as well as things like USB. > kai> - timing of uplink is of utmost importance Well, ALSA doesn't impose any latency of its own so there should be no issue there - the overheads should be minimal. > > the drivers for their particular system (and possibly some unfortunate > > hardware design, it sounds like they may still be bouncing the voice > > call through the AP which isn't the most wonderful idea ever). > > There > Actually, sending data through AP is _very_ good idea from security > perspective. You don't want hacked baseband to eavesdrop on you, do > you? Given that the baseband is a key part of the data path it's not like you're gaining anything there as far as I can see? I suppose you could argue that the AP is actually an additional attack surface here. --pMCBjikF2xGw87uL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJVu7XMAAoJECTWi3JdVIfQ6v0H/2SYlzE2oBrBqoWi+p+T1aVE ZxAMmtVZEcZtwSCtUba//HACyhyF7c0/sr1Hgw9CIFR4lYvFi65GQM+2uDMOj9y/ 9f43n307u0FfvajMAwn0e5wCqx2Hd1kU26QH1KOs7nzxtplGyr4ITRcBXiAE9y4j 52aGk32yoYOTp5kLRaEj/pTOM5ZEPxGCzpc9o4afXVA3sjyJVid5hfkB/x4hv0Ns uXmQg1RVh4SAMmeQLuwL9P675+IUsvTLZJPFDoj6VhYPNGEw6/9FdpyP5lS5x3it 0aww97dIIsVrLVahzNwCbMiAYy39DtqgAP5f37LpatgCQP3GV/1cLgS3IASslnk= =6PVz -----END PGP SIGNATURE----- --pMCBjikF2xGw87uL--