If I remember I2C correctly, that is actually over-complicated. The master selects a device by emitting an address onto the bus, possibly writes some number of bytes to that device (a device-internal register number and/or data to write), and possibly reads some number of bytes from that device. The bus then returns to idle state.

So the manager only needs a slave-address/write-buffer/read-count 3-tuple to define a transaction that can be performed atomically. If read-count is zero, only a completion can be returned; otherwise, the data read from the device is returned. In pseudo-C with the uint8_t[] type as a Perl-like scalar that carries its own length, an I2C transaction has this prototype:

uint8_t[] i2c_xact(i2c_address slave, uint8_t[] write, size_t read_count);

In reply to Re^2: i2c bus contention by jcb
in thread i2c bus contention by anita2R

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