SPI2 input data retrieval

jkeller

Hi,
Does the SPI2 driver introduced with 4.0 still have an option for asynchronous data retrieval?
Since read() consumes all the slack, it seems to correspond to the read_sync() command from the old implementation.

From the documentation, it's not clear to me where the input data is stored between the physical transfer and calls to read(), and how much space is available there (i.e. how many bits can I transfer via MISO before I need to retrieve them with read()?)

Thanks,
Jonas

sb10q

The only place where data is retrieved is via the rtio_input_data syscall (see the SPI2 driver source), which does block until data is available (see artiq/firmware/ksupport/rtio.rs).
The amount of space available depends on how the input RTIO FIFO was created. What system are you using?

jkeller

Thanks for the explanation - am I right to assume then that the limit is an amount of input events (i.e. write() commands with SPI_INPUT set), rather than an amount of transferred bits?
We're using a KC705 with the nist_qc2 binaries, version 4.0 0+gitbf50dcf7.