ALSA: doc: improved docs about quirk_flags in snd-usb-audio

Just briefly described about the option's change and its new usage.

Signed-off-by: Cryolitia PukNgae <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

Documentation/sound/alsa-configuration.rst

···
     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.
+    The option provides a refined and flexible control for applying quirk
+    flags.  It allows to specify the quirk flags for each device, and can
+    be modified dynamically via sysfs.
+    The old usage accepts an array of integers, each of which applies quirk
+    flags on the device in the order of probing.
+    E.g., ``quirk_flags=0x01,0x02`` applies get_sample_rate to the first
+    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 can be
+    specified as ``*`` to match any value.  ``FLAGSx`` can be a set of
+    flags given by name, separated by ``|``, or a hexadecimal number
+    representing the bit flags.  The available flag names are listed below.
+    An exclamation mark can be prefixed to a flag name to negate the flag.
+    For example, ``1234:abcd:mixer_playback_min_mute|!ignore_ctl_error;*:*:0x01;``
+    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: 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
+        * bit 0: ``get_sample_rate``
+          Skip reading sample rate for devices
+        * 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
+        * 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 close interface during setting sample rate
+        * 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``
+          Similar to bit 24 but for capture streams
 
 This module supports multiple devices, autoprobe and hotplugging.