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X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============1341040737906988449==" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org --===============1341040737906988449== Content-Type: multipart/signed; boundary=8a808a06b4a953b5d20dec0ffee61d2775fd30a9d99a11e1a9dc7451dbff; micalg=pgp-sha512; protocol="application/pgp-signature" Content-Transfer-Encoding: 8bit --8a808a06b4a953b5d20dec0ffee61d2775fd30a9d99a11e1a9dc7451dbff Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 > I traced the probe path and confirmed that snd_soc_dai_stream_valid() > is called from soc_new_pcm(). > However, I still couldn't see where a nonzero channels_min alone leads > to creating a capture substream > without an RX DMA channel. > To avoid confusion, I'm referring specifically to the DMA-based > configuration, not PIO mode. > Could you point me to the relevant call path? More precisely, channels_min alone is not sufficient. The codec DAI must also support capture (or be the dummy DAI for a dynamic link), and the link must not be playback_only. Under those conditions, the path is: soc_new_pcm() -> soc_get_playback_capture() -> soc_create_pcm(..., capture =3D 1) -> snd_pcm_new() -> snd_pcm_new_stream(CAPTURE, 1) -> snd_soc_pcm_component_new() -> dmaengine_pcm_new() dmaengine_pcm_request_chan_of() tolerates a missing "rx" channel and leaves pcm->chan[CAPTURE] NULL. Once the capture substream exists, dmaengine_pcm_new() returns -EINVAL with "Missing dma channel for stream: 1". The conditional initialization prevents the CPU DAI from advertising that direction for a tx-only node. - Troy --8a808a06b4a953b5d20dec0ffee61d2775fd30a9d99a11e1a9dc7451dbff Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iIMEABYKACsWIQSL4Ay2cExaPXAQcU2YCe+A+TM0LwUCanG3xg0caUB0cm95LXku b3JnAAoJEJgJ74D5MzQv3rsA/2enFw0bQFhdVHzqRfjGAS8XMICv20KQTtx7sWDo HgV6AQCJZ2ce17LUExbaXiGqo5RUP6KShzKJeeVv+oVziPH8DQ== =AgpX -----END PGP SIGNATURE----- --8a808a06b4a953b5d20dec0ffee61d2775fd30a9d99a11e1a9dc7451dbff-- --===============1341040737906988449== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv --===============1341040737906988449==--