Example:
Sound Cards:
::
0 [SM8250MTPWCD938]: sm8250 - SM8250-MTP-WCD9380-WSA8810-VA-D
SM8250-MTP-WCD9380-WSA8810-VA-DMIC
1 [Seri ]: USB-Audio - Plantronics Blackwire 3225 Seri
Plantronics Plantronics Blackwire
3225 Seri at usb-xhci-hcd.1.auto-1.1,
full sp
2 [C320M ]: USB-Audio - Plantronics C320-M
Plantronics Plantronics C320-M at usb-xhci-hcd.1.auto-1.2, full speed
PCM Devices:
::
card 0: SM8250MTPWCD938 [SM8250-MTP-WCD9380-WSA8810-VA-D], device 0: MultiMedia1 (*) []
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: SM8250MTPWCD938 [SM8250-MTP-WCD9380-WSA8810-VA-D], device 1: MultiMedia2 (*) []
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: Seri [Plantronics Blackwire 3225 Seri], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 2: C320M [Plantronics C320-M], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0
USB Sound Card - card#1:
::
USB Offload Playback Card Route PCM#0 -1 (range -1->32)
USB Offload Playback PCM Route PCM#0 -1 (range -1->255)
USB Sound Card - card#2:
::
USB Offload Playback Card Route PCM#0 0 (range -1->32)
USB Offload Playback PCM Route PCM#0 1 (range -1->255)
The above example shows a scenario where the system has one ASoC platform card (card#0) and two USB sound devices connected (card#1 and card#2). When reading the available kcontrols for each USB audio device, the following kcontrols lists the mapped offload card and pcm device indexes for the specific USB device:
``USB Offload Playback Card Route PCM#*``
``USB Offload Playback PCM Route PCM#*``
The kcontrol is indexed, because a USB audio device could potentially have several PCM devices. The above kcontrols are defined as:
USB Offload Playback Card Route PCM# (R): Returns the ASoC platform sound card index for a mapped offload path. The output “0” (card index) signifies that there is an available offload path for the USB SND device through card#0. If “-1” is seen, then no offload path is available for the USB SND device. This kcontrol exists for each USB audio device that exists in the system, and its expected to derive the current status of offload based on the output value for the kcontrol along with the PCM route kcontrol.
USB Offload Playback PCM Route PCM# (R): Returns the ASoC platform sound PCM device index for a mapped offload path. The output “1” (PCM device index) signifies that there is an available offload path for the USB SND device through PCM device#0. If “-1” is seen, then no offload path is available for the USB\ SND device. This kcontrol exists for each USB audio device that exists in the system, and its expected to derive the current status of offload based on the output value for this kcontrol, in addition to the card route kcontrol.