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Received: from cpc102320-sgyl38-2-0-cust46.18-2.cable.virginm.net ([82.37.168.47] helo=ypsilon.sirena.org.uk) by heliosphere.sirena.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1hqhmj-0003OO-My; Thu, 25 Jul 2019 17:44:09 +0000 Received: by ypsilon.sirena.org.uk (Postfix, from userid 1000) id 315802742B5F; Thu, 25 Jul 2019 18:44:09 +0100 (BST) Date: Thu, 25 Jul 2019 18:44:09 +0100 From: Mark Brown To: Maxime Ripard Subject: Re: Best representation for TDM devices Message-ID: <20190725174409.GF4213@sirena.org.uk> References: <20190725130112.3j2vi4dyngyr6yh3@flea> MIME-Version: 1.0 In-Reply-To: <20190725130112.3j2vi4dyngyr6yh3@flea> X-Cookie: Jenkinson's Law: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190725_104414_696805_45AAC25C X-CRM114-Status: GOOD ( 14.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alsa-devel@alsa-project.org, Alexandre Belloni , Takashi Iwai , Liam Girdwood , Chen-Yu Tsai , Thomas Petazzoni , Jaroslav Kysela , linux-arm-kernel@lists.infradead.org Content-Type: multipart/mixed; boundary="===============1518461609711075358==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============1518461609711075358== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="cpvLTH7QU4gwfq3S" Content-Disposition: inline --cpvLTH7QU4gwfq3S Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Jul 25, 2019 at 03:01:12PM +0200, Maxime Ripard wrote: > Since I have two codecs, I have two links (described through > simple-card) and thus two subdevices. However, the microphones > connected are really separate streams, so ideally (I guess?) we should > have 1 subdevice per microphone. > An alternative would be that we capture the whole 4 channels and use > dsnoop to demux them, but trying to use the device directly (using > arecord -D hw:0) results in the ioctl to change the number of channels > being rejected, I'm assuming because each codec only has 2 channels? > So I'm a bit lost at this point about how I should go and expose > this. I couldn't really find any similar setup either in the > kernel. Any preferred way of doing this? What is the actual hardware - what do the microphones physically look like in the system, what functional role do they play? My initial guess would be to combine them into a single PCM for userspace, there's some support for that but it's not surprising if that's broken somewhere along the line as it's very infrequently tested. --cpvLTH7QU4gwfq3S Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAl056mgACgkQJNaLcl1U h9C4xgf/ecGx+yNE7q7BDjXryu/S2MaP2MoLVGeNAfqFdg6Q37hZnvDBkvS1FclU ZhvpOy6AmwKHeMEsjIi6nloIBgwAy4xuuTC196fRfZPF6vm8anCEkNgy50L+1LHL aMumVuDGg+lhdwpw9nNs+7Igf5aPYQ9GtNMRqO7Fzzlc016IzfwZfVuGTGLtmKYb UPuDnCjbAfZ2y3bd4R2N6upPwykZQEobYTKg6bKecYw/m16OMlayRyXw7Cl/jjQ1 Qc/zIcgcAlPjJGdDmhmU0q9ekigKN9h2oXcyEOFXnHH3ofxa/Pv1NCnlIdjV29+L VuBX4FLparLISadUL8FIIwxuvGUaZA== =XGrz -----END PGP SIGNATURE----- --cpvLTH7QU4gwfq3S-- --===============1518461609711075358== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============1518461609711075358==--