Re: [PATCH v4 5/5] ALSA: doc: add docs about improved quirk_flags in snd-usb-audio

[Randy Dunlap <rdunlap@infradead.org>]

Hi--

On 9/18/25 2:24 AM, Cryolitia PukNgae via B4 Relay wrote:
> From: Cryolitia PukNgae <cryolitia@uniontech.com>
> 
> Just briefly described about the option.
> 
> Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.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?

> +    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.

> +        * 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.
-- 
~Randy