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Mon, 4 May 2026 11:29:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id bB74JBeD+GnCHQAAD6G6ig (envelope-from ); Mon, 04 May 2026 11:29:27 +0000 Date: Mon, 04 May 2026 13:29:27 +0200 Message-ID: <87tssnxvjc.wl-tiwai@suse.de> From: Takashi Iwai To: Anton Swart Cc: Jaroslav Kysela , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ALSA: usb-audio: Add quirk flags for AlphaTheta EUPHONIA In-Reply-To: <20260503211517.14332-1-anton.swart.jhb@gmail.com> References: <20260503211517.14332-1-anton.swart.jhb@gmail.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-2.01 / 50.00]; BAYES_HAM(-3.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_RATELIMITED(0.00)[rspamd.com]; FREEMAIL_TO(0.00)[gmail.com]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DWL_DNSWL_BLOCKED(0.00)[suse.de:dkim]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; RCPT_COUNT_THREE(0.00)[4]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:mid,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns] X-Rspamd-Queue-Id: C43276B0EA X-Spam-Flag: NO X-Spam-Score: -2.01 X-Spam-Level: On Sun, 03 May 2026 23:15:17 +0200, Anton Swart wrote: > > The AlphaTheta EUPHONIA (VID 0x2b73, PID 0x0047) is a USB Audio > Class 2 DJ mixer that requires implicit feedback for full-duplex > operation. The capture endpoint (0x83 IN, interface 2) acts as the > implicit feedback source for the playback endpoint (0x03 OUT, > interface 1), and the device firmware does not send isochronous > data on the capture endpoint unless the host is simultaneously > sending data on the playback endpoint, i.e. playback must be > started first. > > Without QUIRK_FLAG_PLAYBACK_FIRST the kernel waits for capture URBs > before submitting playback URBs, creating a deadlock: the device > waits for playback data and the host waits for capture data. > Without QUIRK_FLAG_GENERIC_IMPLICIT_FB the kernel does not detect > the implicit feedback relationship between the two interfaces. > > The same flag combination is already used for the Behringer UMC202HD, > UMC204HD and UMC404HD (0x1397:0x0507/0x0508/0x0509), which exhibit > the identical implicit-feedback topology. > > Tested on Raspberry Pi 5 with kernel 6.12.75; continuous full-duplex > streaming at 96 kHz / 24-bit, zero XRUNs. > > Signed-off-by: Anton Swart Applied now. Thanks. Takashi