Document source: 51e93508f22f; code reference: 51e93508f22f. 中文. Source language: en; requested: en; actual: en; translation: original.

Source documentation does not establish software or physical hardware qualification. See the support and qualification records for their exact scope.

Multiple controller ownership

The public I/O faces keep their existing operation tables and caller-owned request contracts. Selecting another physical controller creates another private provider instance, not another transport abstraction or global registry. An instance’s cold register, clock, DMA and IRQ facts remain immutable until its publisher set has been withdrawn and the instance stopped.

I2C V1 IRQ and finite DMA

STM32F407 I2C1 and I2C2, and GD32F470 I2C0 and I2C1, execute the same maintained V1 register algorithm. Per-controller cold wrappers validate all register pointers, DATA offsets, line inputs, bus clocks and DMA selectors against the actual SDK. Their EV, ER, RX DMA and TX DMA IRQs come from the selected controller identity. Initialization of an already enabled physical controller returns BUSY before changing its control registers or IRQ priorities.

SoC controller	GPIOB pins and AF	Peripheral clock	Finite RX / TX route
STM32F407 I2C1	PB6/PB7 or PB8/PB9, AF4	42 MHz	DMA1 stream0 / stream6, channel1
STM32F407 I2C2	PB10/PB11, AF4	42 MHz	DMA1 stream2 / stream7, channel7
GD32F470 I2C0	PB6/PB7 or PB8/PB9, AF4	50 MHz	DMA0 channel0 / channel6, selector1
GD32F470 I2C1	PB10/PB11, AF4	50 MHz	DMA0 channel2 / channel7, selector7

GD32 names in this table are the vendor’s literal DMA0/DMA1 names. The platform configuration’s opaque controller IDs use a separate mapping. A DMA request selector never identifies or allocates a memory engine. Static cold assembly must reject other devices that select an already owned physical engine.

Setting the private state’s DMA descriptor to NULL selects IRQ-only messages and acquires no DMA vector. Exact immutable macros NX_STM32_I2C2_DMA(regions, count) and NX_GD32_I2C1_DMA(regions, count) select the secondary finite routes. The initialization API is unchanged. Pin, bus clock, DMA clock and shared resource leases remain cold assembly’s responsibility; the provider does not silently allocate these resources.

Each request retains its descriptor, messages, buffers and endpoint until that controller’s engine, interrupt sources and wire have drained. Completing or cancelling one instance cannot acknowledge another stream’s W1C flags, disable its vectors, release its request or change its wake sink. A refused DMA disable retains only the affected instance’s borrow in DRAINING or QUARANTINED; elapsed time does not prove hardware quiescence.

The shared DMA acknowledge leaf compiles to a direct selected register write. Its test override models the real W1C side effect rather than treating a clear register as ordinary RAM. There is no per-byte MMIO operation table or new mutable field. Actual Cortex-M4F compilation measures the unchanged state at 56 bytes, endpoint at 8 bytes and optional immutable DMA descriptor at 80 bytes. The provider and shared algorithm objects contain zero global DATA/BSS. Selected object text size is evidence of a compiled object, not an entire image’s retained Flash size or a cycle measurement.

The reviewed silicon route sources are STM32 RM0090 Rev22 Table 43 and GD32F4xx User Manual Rev3.3 Tables 10-2 and 10-3. These facts do not establish a board’s external wiring. Secondary-board routes require an explicit reviewed board configuration. Host tests model external CPU/MMIO behavior, and real ARM compilation uses actual vendor SDK headers. Bus timing, electrical levels and DMA contention still need hardware qualification; no physical result is claimed here.