Audio control transfers misaligned on some platforms

[sodank808]

Operating System

Others

Board

ESP32-S3

Firmware

Probably the most relevant example is uac2_headset.

What happened ?

After the 0.18.0 release, certain platforms such as iOS fail to record the microphone because the endpoint stalls. This was root caused to missing 4 byte alignment on the ctrl_buf_1 buffer in audio_device.c. It seems that this changed in #2865 but it is unclear why it was changed, probably a mistake.

How to reproduce ?

Record microphone in a USB audio class 2.0 example. The original replication was on iOS in voice memo. Unfortunately, alignment issues can be finicky and depend on the arrangement of memory performed by the linker.

Debug Log as txt file (LOG/CFG_TUSB_DEBUG=2)

Unfortunately, the device under test does not have logging piped out.

Screenshots

In the USB analyzer, I was able to clue in to the issue when the IN endpoint stopped sending data right after a control transfer

I have checked existing issues, dicussion and documentation

• I confirm I have checked existing issues, dicussion and documentation.

[HiFiPhile]

Hi, with a first look I think the issue should be elsewhere, since with DWC2 IP (used by ESP32) there isn't an alignment requirement for control transfer buffer. Also data buffer aligment is only needed when DMA is enabled.

It looks more like an incomplete iso transfer (You can search Incomplete isochronous in STM32's manual like RM0477 which has more details than ESP32.)

Meanwhile ctrl_buf_1 should be aligned for some NXP MCUs

[HiFiPhile]

UAC ctrl buffer alignment fixed in #3034.