STM32H7B0VB Using I2S on SPI6 with BDMA2 causes panic.

[evaneidt]

When initializing I2S on peripheral SPI6 only supports DMA channels BDMA2_CH(0-7). Configuring the I2S peripheral through new_rxonly() causes a panic in dma mod.rs:97 with error "index out of bounds: the len is 24 but the index is 24". It appears this line is attempting to read the DMA_CHANNELS array that is generated by embassy_stm32. This is reached when i2s.rs is configuring the RX dma buffer.

In embassy-stm32 build.rs the comment on line 1624 ("// Some H7 chips have BDMA1 hardcoded for DFSDM, ie no DMAMUX. It's unsupported, skip it.") could be showing the issue. It appears as if the channel count is being undercounted as a result of this skipping, leading to the invalid index. Possibly this skipping is no longer needed (array length is shorter than it should be), or some other part of the code should be doing this skipping that isn't (index is longer than it should be).

I am unfortunately unfamiliar with this codebase and too inexperienced with Rust as a whole to suggest how this might be fixed, but I believe this to be the root cause.