USBAudioBackend Class Reference

Abstract seam for every raw USB-stack call the UAC2 driver (USBAudioDeviceBase) needs. Concrete subclasses wrap TinyUSB (USBAudioBackendTinyUSB, today) or a native peripheral driver (STM32 HAL / Renesas USBFS — future work). More...

#include <USBAudioBackend.h>

Inheritance diagram for USBAudioBackend:

Public Member Functions
virtual	~USBAudioBackend ()=default
virtual bool	claimEndpoint (uint8_t rhport, uint8_t ep_addr)=0
virtual bool	clearStall (uint8_t rhport, uint8_t ep_addr)=0
	Clear a halted/stalled condition on an endpoint.
virtual bool	closeEndpoint (uint8_t rhport, uint8_t ep_addr)=0
virtual bool	controlStatus (uint8_t rhport, const UsbSetupPacket &request)=0
	Send a zero-length-packet status acknowledgement.
virtual bool	controlTransfer (uint8_t rhport, const UsbSetupPacket &request, uint8_t *buffer, uint16_t length)=0
	Complete a GET/SET control transfer's data stage with buffer.
virtual void	enableSof (uint8_t rhport, bool enable)=0
bool	isFullSpeed () const
	Convenience: speed() == UsbSpeed::Full.
bool	isHighSpeed () const
	Convenience: speed() == UsbSpeed::High.
virtual bool	isoActivateEndpoint (uint8_t rhport, const UsbEndpointDescriptorView &ep)=0
virtual bool	isoAllocEndpoint (uint8_t rhport, uint8_t ep_addr, uint16_t max_packet_size)=0
virtual bool	mounted () const =0
	True once the device has completed USB enumeration.
virtual bool	openEndpoint (uint8_t rhport, const UsbEndpointDescriptorView &ep)=0
virtual bool	releaseEndpoint (uint8_t rhport, uint8_t ep_addr)=0
virtual UsbSpeed	speed () const =0
	Current negotiated bus speed.
virtual bool	transfer (uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t length)=0
virtual bool	usesIsoAlloc () const =0

Detailed Description

Abstract seam for every raw USB-stack call the UAC2 driver (USBAudioDeviceBase) needs. Concrete subclasses wrap TinyUSB (USBAudioBackendTinyUSB, today) or a native peripheral driver (STM32 HAL / Renesas USBFS — future work).

Only linear-buffer transfers are supported — there is no FIFO-mode transfer API.

Author

Phil Schatzmann

Copyright

GPLv3

Constructor & Destructor Documentation

~USBAudioBackend()

virtual ~USBAudioBackend ( )

virtualdefault

Member Function Documentation

claimEndpoint()

virtual bool claimEndpoint ( uint8_t  rhport, uint8_t  ep_addr  )

pure virtual

True if the endpoint is currently free to accept a new transfer (used to gate feedback sends from the SOF ISR).

Implemented in USBAudioBackendTinyUSB.

clearStall()

virtual bool clearStall ( uint8_t  rhport, uint8_t  ep_addr  )

pure virtual

Clear a halted/stalled condition on an endpoint.

Implemented in USBAudioBackendTinyUSB.

closeEndpoint()

virtual bool closeEndpoint ( uint8_t  rhport, uint8_t  ep_addr  )

pure virtual

Close a previously opened endpoint. Only called when usesIsoAlloc() is false (backends using iso-alloc keep the endpoint reserved and just re-activate it on the next alt-setting).

Implemented in USBAudioBackendTinyUSB.

controlStatus()

virtual bool controlStatus ( uint8_t  rhport, const UsbSetupPacket &  request  )

pure virtual

Send a zero-length-packet status acknowledgement.

Implemented in USBAudioBackendTinyUSB.

controlTransfer()

virtual bool controlTransfer ( uint8_t  rhport, const UsbSetupPacket &  request, uint8_t *  buffer, uint16_t  length  )

pure virtual

Complete a GET/SET control transfer's data stage with buffer.

Implemented in USBAudioBackendTinyUSB.

enableSof()

virtual void enableSof ( uint8_t  rhport, bool  enable  )

pure virtual

Enable/disable the start-of-frame interrupt for the audio feedback consumer. Backends without a SOF concept (e.g. one that polls instead) may implement this as a no-op, but must then drive the feedback-interval logic themselves — not a concern for the TinyUSB backend.

Implemented in USBAudioBackendTinyUSB.

isFullSpeed()

bool isFullSpeed ( ) const

inline

Convenience: speed() == UsbSpeed::Full.

isHighSpeed()

bool isHighSpeed ( ) const

inline

Convenience: speed() == UsbSpeed::High.

isoActivateEndpoint()

virtual bool isoActivateEndpoint ( uint8_t  rhport, const UsbEndpointDescriptorView &  ep  )

pure virtual

Activate a previously iso-allocated endpoint for the given descriptor (arms it to accept traffic at the given alt setting's packet size).

Implemented in USBAudioBackendTinyUSB.

isoAllocEndpoint()

virtual bool isoAllocEndpoint ( uint8_t  rhport, uint8_t  ep_addr, uint16_t  max_packet_size  )

pure virtual

Reserve buffer space for an isochronous endpoint. Only called when usesIsoAlloc() is true. Safe to call once per endpoint lifetime.

Implemented in USBAudioBackendTinyUSB.

mounted()

virtual bool mounted ( ) const

pure virtual

True once the device has completed USB enumeration.

Implemented in USBAudioBackendTinyUSB.

openEndpoint()

virtual bool openEndpoint ( uint8_t  rhport, const UsbEndpointDescriptorView &  ep  )

pure virtual

Open a non-isochronous endpoint (used for the AC interrupt EP, and for data endpoints on backends where usesIsoAlloc() is false).

Implemented in USBAudioBackendTinyUSB.

releaseEndpoint()

virtual bool releaseEndpoint ( uint8_t  rhport, uint8_t  ep_addr  )

pure virtual

Release the busy/claim flag on an iso endpoint without closing it (used right after a pre-activation during enumeration so a later transfer can arm normally).

Implemented in USBAudioBackendTinyUSB.

speed()

virtual UsbSpeed speed ( ) const

pure virtual

Current negotiated bus speed.

Implemented in USBAudioBackendTinyUSB.

transfer()

virtual bool transfer ( uint8_t  rhport, uint8_t  ep_addr, uint8_t *  buffer, uint16_t  length  )

pure virtual

Arm one linear-buffer IN or OUT transfer. buffer must stay valid until the transfer-complete callback fires. Returns false if the endpoint could not be armed (already busy, not open, etc).

Implemented in USBAudioBackendTinyUSB.

usesIsoAlloc()

virtual bool usesIsoAlloc ( ) const

pure virtual

True if this backend must pre-allocate iso endpoint buffer space once (in audiod_open) and only (re)activate it on each SET_INTERFACE, rather than open/close per alt-setting (mirrors TinyUSB's TUP_DCD_EDPT_ISO_ALLOC platform capability). Lets the UAC2 driver pick one code path at runtime instead of branching on a preprocessor macro.

Implemented in USBAudioBackendTinyUSB.

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The documentation for this class was generated from the following file:

• src/AudioTools/Communication/USB/USBAudioBackend.h