linux-kernel - [PATCH 2/2] ALSA: docs: Add documents for recently changes in snd-usb-audio

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Message-Id: <20250829-sound-param-v1-2-3c2f67cd7c97@uniontech.com>
Date: Fri, 29 Aug 2025 13:11:00 +0800
From: Cryolitia PukNgae via B4 Relay <devnull+cryolitia.uniontech.com@...nel.org>
To: Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>, 
 Jonathan Corbet <corbet@....net>
Cc: linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Mingcong Bai <jeffbai@...c.io>, Kexy Biscuit <kexybiscuit@...c.io>, 
 Wang Yuli <wangyuli@...pin.org>, Guan Wentao <guanwentao@...ontech.com>, 
 Nie Cheng <niecheng1@...ontech.com>, Zhan Jun <zhanjun@...ontech.com>, 
 Celeste Liu <CoelacanthusHex@...il.com>, Guoli An <anguoli@...ontech.com>, 
 linux-doc@...r.kernel.org, Cryolitia PukNgae <cryolitia@...ontech.com>
Subject: [PATCH 2/2] ALSA: docs: Add documents for recently changes in
 snd-usb-audio

From: Cryolitia PukNgae <cryolitia@...ontech.com>

Changed:
  - ignore_ctl_error
  - lowlatency
  - skip_validation
  - mixer_min_mute
  - quirk_flags[19:24]

Signed-off-by: Cryolitia PukNgae <cryolitia@...ontech.com>
---
 Documentation/sound/alsa-configuration.rst | 35 ++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst
index a45174d165ebdeadd89de5f556483465c5f6e808..35b288a22e2e6d869f79ba12914b4ee6b538a6c6 100644
--- a/Documentation/sound/alsa-configuration.rst
+++ b/Documentation/sound/alsa-configuration.rst
@@ -2253,8 +2253,15 @@ device_setup
     Default: 0x0000 
 ignore_ctl_error
     Ignore any USB-controller regarding mixer interface (default: no)
+    ``ignore_ctl_error=1`` may help when you get an error at accessing
+    the mixer element such as URB error -22.  This happens on some
+    buggy USB device or the controller.  This workaround corresponds to
+    the ``quirk_flags`` bit 14, too.
 autoclock
     Enable auto-clock selection for UAC2 devices (default: yes)
+lowlatency
+    Enable low latency playback mode (default: yes).
+    Could disable it to switch back to the old mode if face a regression.
 quirk_alias
     Quirk alias list, pass strings like ``0123abcd:5678beef``, which
     applies the existing quirk for the device 5678:beef to a new
@@ -2284,6 +2291,17 @@ delayed_register
     The driver prints a message like "Found post-registration device
     assignment: 1234abcd:04" for such a device, so that user can
     notice the need.
+skip_validation
+    Skip unit descriptor validation (default: no).
+    The option is used to ignores the validation errors with the hexdump
+    of the unit descriptor instead of a driver probe error, so that we
+    can check its details.
+mixer_min_mute
+    Treat the minimum volume control value as mute (default: no).
+    ``mixer_min_mute=1`` may help when you find the audio mutes when
+    the volume is below a certain threshold.  This happens commonly with
+    USB audio devices.  This workaround corresponds to the ``quirk_flags``
+    bit 24, too.
 quirk_flags
     Contains the bit flags for various device specific workarounds.
     Applied to the corresponding card index.
@@ -2307,6 +2325,16 @@ quirk_flags
         * bit 16: Set up the interface at first like UAC1
         * bit 17: Apply the generic implicit feedback sync mode
         * bit 18: Don't apply implicit feedback sync mode
+        * bit 19: Don't closed interface during setting sample rate
+        * bit 20: Force an interface reset whenever stopping & restarting
+          a stream
+        * bit 21: Do not set PCM rate (frequency) when only one rate is
+          available for the given endpoint.
+        * bit 22: Set the fixed resolution 16 for Mic Capture Volume
+        * bit 23: Set the fixed resolution 384 for Mic Capture Volume
+        * bit 24: Set minimum volume control value as mute for devices
+          where the lowest playback value represents muted state instead
+          of minimum audible volume
 
 This module supports multiple devices, autoprobe and hotplugging.
 
@@ -2314,10 +2342,9 @@ NB: ``nrpacks`` parameter can be modified dynamically via sysfs.
 Don't put the value over 20.  Changing via sysfs has no sanity
 check.
 
-NB: ``ignore_ctl_error=1`` may help when you get an error at accessing
-the mixer element such as URB error -22.  This happens on some
-buggy USB device or the controller.  This workaround corresponds to
-the ``quirk_flags`` bit 14, too.
+NB: ``ignore_ctl_error=1`` and ``mixer_min_mute=1`` just provides A
+quick way to work around the issues.  If you have a buggy device that
+requires these quirks, please report it to the upstream.
 
 NB: ``quirk_alias`` option is provided only for testing / development.
 If you want to have a proper support, contact to upstream for

-- 
2.51.0