Message-ID: <E5D6C740C99059BF+af37f938-2e5d-4d41-adbc-a0c000d432fd@uniontech.com>
Date: Fri, 19 Sep 2025 09:43:37 +0800
From: Cryolitia PukNgae <cryolitia@...ontech.com>
To: Randy Dunlap <rdunlap@...radead.org>, Jaroslav Kysela <perex@...ex.cz>,
 Takashi Iwai <tiwai@...e.com>, Jonathan Corbet <corbet@....net>,
 Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>,
 Daniel Gomez <da.gomez@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>
Cc: linux-sound@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 Mingcong Bai <jeffbai@...c.io>, Kexy Biscuit <kexybiscuit@...c.io>,
 Nie Cheng <niecheng1@...ontech.com>, Zhan Jun <zhanjun@...ontech.com>,
 Feng Yuan <fengyuan@...ontech.com>, qaqland <anguoli@...ontech.com>,
 kernel@...ontech.com, linux-modules@...r.kernel.org
Subject: Re: [PATCH v4 5/5] ALSA: doc: add docs about improved quirk_flags in
 snd-usb-audio

Thanks for your review. I'll waiting some reviews on other patches and resend
a new version about it.

On 19/09/2025 04.21, Randy Dunlap wrote:
> Hi--
> 
> On 9/18/25 2:24 AM, Cryolitia PukNgae via B4 Relay wrote:
>> From: Cryolitia PukNgae <cryolitia@...ontech.com>
>>
>> Just briefly described about the option.
>>
>> Signed-off-by: Cryolitia PukNgae <cryolitia@...ontech.com>
>> ---
>>  Documentation/sound/alsa-configuration.rst | 108 ++++++++++++++++++++---------
>>  1 file changed, 75 insertions(+), 33 deletions(-)
>>
>> diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst
>> index a2fb8ed251dd0294e7a62209ca15d5c32c6adfae..efffe3d534beeddcb6a47ac27a24defb6879f534 100644
>> --- a/Documentation/sound/alsa-configuration.rst
>> +++ b/Documentation/sound/alsa-configuration.rst
>> @@ -2297,39 +2297,81 @@ skip_validation
>>      of the unit descriptor instead of a driver probe error, so that we
>>      can check its details.
>>  quirk_flags
>> -    Contains the bit flags for various device specific workarounds.
>> -    Applied to the corresponding card index.
>> -
>> -        * bit 0: Skip reading sample rate for devices
>> -        * bit 1: Create Media Controller API entries
>> -        * bit 2: Allow alignment on audio sub-slot at transfer
>> -        * bit 3: Add length specifier to transfers
>> -        * bit 4: Start playback stream at first in implement feedback mode
>> -        * bit 5: Skip clock selector setup
>> -        * bit 6: Ignore errors from clock source search
>> -        * bit 7: Indicates ITF-USB DSD based DACs
>> -        * bit 8: Add a delay of 20ms at each control message handling
>> -        * bit 9: Add a delay of 1-2ms at each control message handling
>> -        * bit 10: Add a delay of 5-6ms at each control message handling
>> -        * bit 11: Add a delay of 50ms at each interface setup
>> -        * bit 12: Perform sample rate validations at probe
>> -        * bit 13: Disable runtime PM autosuspend
>> -        * bit 14: Ignore errors for mixer access
>> -        * bit 15: Support generic DSD raw U32_BE format
>> -        * 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
>> -        * bit 25: Be similar to bit 24 but for capture streams
>> +    The option provides a refined and flexible control for applying quirk
>> +    flags.  It allows to specify the quirk flags for each device, and could
> 
>                                                                      and may
> or: and can
> 
>> +    be modified dynamically via sysfs.
>> +    The old usage accepts an array of integers, each of which apply quirk
> 
>                                                                  applies
> 
>> +    flags on the device in the order of probing.
>> +    e.g. ``quirk_flags=0x01,0x02`` applies get_sample_rate to the first
> 
>        E.g.,
> 
>> +    device, and share_media_device to the second device.
>> +    The new usage accepts a string in the format of
>> +    ``VID1:PID1:FLAGS1;VID2:PID2:FLAGS2;...``, where ``VIDx`` and ``PIDx``
>> +    specify the device, and ``FLAGSx`` specify the flags to be applied.
>> +    ``VIDx`` and ``PIDx`` are 4-digit hexadecimal numbers, and could be
> 
>                                                            s/could/may/
> 
>> +    specified as ``*`` to match any value.  ``FLAGSx`` could be a set of
> 
>                                                       s/could/may/
> 
>> +    flags given by name, separated by ``|``, or a hexadecimal number
>> +    representing the bit flags.  The available flag names are listed above.
> 
>                                                               s/above/below/ ?
> 
>> +    An exclamation mark could be prefixed to a flag name to negate the flag.
>                        s/could/may/
> 
>> +    For example, ``1234:abcd:mixer_playback_min_mute|!ignore_ctl_error;*:*:0x01;``
> 
> What happens if the trailing (ending) ';' is omitted?

This is where I found something strange when I was testing it myself. When I use
`echo '*:*:mixer_playback_min_mute` > /sys/module/snd_usb_audio/parameters/quirk_flags`,
the string received by the driver contains a lot of trailing spaces. I am not familiar
with the kernel and don't know how to handle this situation. Simply adding a semicolon
to the input will make the trailing spaces after the semicolon be ignored.

> 
>> +    applies the ``mixer_playback_min_mute`` flag and clears the
>> +    ``ignore_ctl_error`` flag for the device 1234:abcd, and applies the
>> +    ``skip_sample_rate`` flag for all devices.
>> +
>> +        * bit 0: ``get_sample_rate``
>> +          Skip reading sample rate for devices
> 
> get vs Skip is a little confusing.

This part is copied from Takashi Iwai[1]. It does a little confusing.

>> +        * bit 1: ``share_media_device``
>> +          Create Media Controller API entries
>> +        * bit 2: ``align_transfer``
>> +          Allow alignment on audio sub-slot at transfer
>> +        * bit 3: ``tx_length``
>> +          Add length specifier to transfers
>> +        * bit 4: ``playback_first``
>> +          Start playback stream at first in implement feedback mode
>> +        * bit 5: ``skip_clock_selector``
>> +          Skip clock selector setup
>> +        * bit 6: ``ignore_clock_source``
>> +          Ignore errors from clock source search
>> +        * bit 7: ``itf_usb_dsd_dac``
>> +          Indicates ITF-USB DSD based DACs
> 
>                                DSD-based
> 
>> +        * bit 8: ``ctl_msg_delay``
>> +          Add a delay of 20ms at each control message handling
>> +        * bit 9: ``ctl_msg_delay_1m``
>> +          Add a delay of 1-2ms at each control message handling
>> +        * bit 10: ``ctl_msg_delay_5m``
>> +          Add a delay of 5-6ms at each control message handling
>> +        * bit 11: ``iface_delay``
>> +          Add a delay of 50ms at each interface setup
>> +        * bit 12: ``validate_rates``
>> +          Perform sample rate validations at probe
>> +        * bit 13: ``disable_autosuspend``
>> +          Disable runtime PM autosuspend
>> +        * bit 14: ``ignore_ctl_error``
>> +          Ignore errors for mixer access
>> +        * bit 15: ``dsd_raw``
>> +          Support generic DSD raw U32_BE format
>> +        * bit 16: ``set_iface_first``
>> +          Set up the interface at first like UAC1
>> +        * bit 17: ``generic_implicit_fb``
>> +          Apply the generic implicit feedback sync mode
>> +        * bit 18: ``skip_implicit_fb``
>> +          Don't apply implicit feedback sync mode
>> +        * bit 19: ``iface_skip_close``
>> +          Don't closed interface during setting sample rate
> 
>                    close
> 
>> +        * bit 20: ``force_iface_reset``
>> +          Force an interface reset whenever stopping & restarting a stream
>> +        * bit 21: ``fixed_rate``
>> +          Do not set PCM rate (frequency) when only one rate is available
>> +          for the given endpoint
>> +        * bit 22: ``mic_res_16``
>> +          Set the fixed resolution 16 for Mic Capture Volume
>> +        * bit 23: ``mic_res_384``
>> +          Set the fixed resolution 384 for Mic Capture Volume
>> +        * bit 24: ``mixer_playback_min_mute``
>> +          Set minimum volume control value as mute for devices where the
>> +          lowest playback value represents muted state instead of minimum
>> +          audible volume
>> +        * bit 25: ``mixer_capture_min_mute``
>> +          Be similar to bit 24 but for capture streams
> 
>              Similar to
> 
>>  
>>  This module supports multiple devices, autoprobe and hotplugging.
>>  
>> Are all of these quirks used on various devices or are some of these
> just implemented just in case they are needed in the future?thanks.

I believe in that all of them are used in quirk_flags_table in sound/usb/quirks.c

1. https://lore.kernel.org/all/20210729073855.19043-2-tiwai@suse.de/

Best regards,
Cryolitia

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