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Tue, 04 Aug 2026 17:59:38 +0800 (CST) X-QQ-SSF: 0000000000000000000000000000000 X-QQ-GoodBg: 0 X-BIZMAIL-ID: 11623012881500782239 EX-QQ-RecipientCnt: 13 Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: multipart/signed; boundary=0cb53cc854d56efd7aaf92f0490d3586ec96bc93b77b8c725886ac6337f3; micalg=pgp-sha512; protocol="application/pgp-signature" Date: Tue, 04 Aug 2026 02:59:36 -0700 Message-Id: Cc: "Yixun Lan" , "Takashi Iwai" , "Mark Brown" , "Jaroslav Kysela" , "Liam Girdwood" , "Goko Mell" , "Jinmei Wei" , "Kuninori Morimoto" , , , , Subject: Re: [PATCH] ASoC: spacemit: Remove redundant DAI field initialization From: "Troy Mitchell" To: "Bui Duc Phuc" References: <20260804043036.22065-1-phucduc.bui@gmail.com> In-Reply-To: Content-Transfer-Encoding: 8bit X-QQ-SENDSIZE: 520 Feedback-ID: zesmtpsz:linux.spacemit.com:qybglogicsvrgz:qybglogicsvrgz3a-0 X-QQ-XMAILINFO: NfGQECF1EzMaHtIWUW+i4t/cJyKGyMJKsST0FnN6c7I25AP2cXYxpo8X 2AYPJXbdzJsH02rXQ98RvXtaOMAylnB9+6HmHNMX+XZI2lOnUEUTR8KK9fpuHOwrd6hjMiw 8X5+BPFC8z8oLwBiW6AKoWqeup5S79jkbWitKXf28NidTfliP9vNHkVBhcamD1dBGRjOFTp wMysaHKm+6/y0gu+BhizbcwSyaGJaAQua4Xl1+/+uUX24G/fc03IbE2zqHtjqkYuT/KDcJb NEtDaJzK7FPrvSy03/0IqFaJ9GKWhho56g8CRC+B27GwPDVwHULozQGgmQWn+3pBObyscq7 KxWxyPKMDRas3SrZntYAi4Z+nda2L1gFbNe5IUBFPam2Aqh1GnVyZbWntUgt05xMqFW9PDz j5cSHPRnat0GvUWeV83USvAmvcEQ9BVM+EAFb2NYqcCvB2PzRi0L9sgStfQa3/zxLc2+Rgd FKGjFwtRb6X+4V67y1wVRgaAO8ia8D957TYu/Bx/nKfh3y0g+RFKFI12YcpUdcEPMEvhRgT SUqTYxP/E/s6eZ8IBjOlVqNveeIqdqyzCb/TSObTDtir9vS+/Aowz4k3k5RpxTS40Bzjn5a lg4C1YPnGtzGguhnSIuiRJhG9FxyOwtxJaHpFkcRZty9cmRWhVct1V/7ZwfaHWuen2aXHaf gft9ShXthmHtnpNVMd0n1o3RYpkawgyM766RtH+tqsQ1ItNm3aw6jomrJcMMLvkJ9Du0eU1 ma2AICoMToOZfcqnc4qju9ADHBw3iahRsWBVd+TxlvOprG0E5Fd6TS7P9Gj72bZRKN2Jj1o +jFUPl0dj2RXw8BKTHSEbsMQyw7EF9p7ciJnVV+6JNYyJeoZsyJ4i/R4Uqd0mrrQaL7usXz 7aCqYBz7APxJF/aFA+b//kam4R1i5yfdO9wlRChNVgmc5A8OyIcwm7KLOsztvIU8xLrWMLQ rK0yly1rfd/uc02yekSDCXOiZb4tQyNDSJXSGHDSD1KNFCxwVh2d0JgvsNZ9L7ndf55s0MB r4YaSxZTDWknm5taCcz6RiFOW/xNy3kJrer9MXCY74vzr+Rz3RdoJRJZ5PX33Qrq2c2E1eZ UDAm83XcaTFE+4aBBOejZLQKyUMGpGW+cBR3Hx5Mr+b9PIS0Eq9TMeaa9uwaPSyqkuKLnVf LorHkbTi+AM6g4k= X-QQ-XMRINFO: MSVp+SPm3vtSI1QTLgDHQqIV1w2oNKDqfg== X-QQ-RECHKSPAM: 0 --0cb53cc854d56efd7aaf92f0490d3586ec96bc93b77b8c725886ac6337f3 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 --0cb53cc854d56efd7aaf92f0490d3586ec96bc93b77b8c725886ac6337f3 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iIMEABYKACsWIQSL4Ay2cExaPXAQcU2YCe+A+TM0LwUCanG4CA0caUB0cm95LXku b3JnAAoJEJgJ74D5MzQvmhgA/iKim769XKKzBMQSQN0e0WT8cDcERmf6hZVpFc2P GucAAQCL7rMgg02LAyIJm55KkoPR7IBfAkfgUjclm5YznSGKCg== =QizS -----END PGP SIGNATURE----- --0cb53cc854d56efd7aaf92f0490d3586ec96bc93b77b8c725886ac6337f3--