ESP32 Forum

Hello,

I am slightly confused by the SPI Master Driver documentation. It is warned that "if multiple tasks try to access the same SPI Device, the driver is not thread-safe." and the recommended workaround are mutexes or refactoring the application as to let the SPI peripheral be only accessed by one task at a time. The terminology section hints that "Device" is understood as a physical device (due signals and CS-lines being mentioned).

Does this apply strictly to physical devices on the SPI bus, or just to logical devices represented by their respective spi_device_handle_t -handles added on the bus with spi_bus_add_device()? I.e. could I have multiple tasks accessing a single physical SPI device in a thread safe manner, given that each task uses it's own logical spi_device_handle_t -handle (and acquiring/releasing the bus for the logical device as needed with spi_device_acquire/release_bus() )?

I am mainly interested in knowing this in order to avoid perhaps totally unnecessary semaphores or mutexes to protect bus access, in case the already existing spi_device_acquire_bus() and multiple handles representing the same physical device would already serve as a way for a task to prevent other tasks from meddling with the bus while it performs its function.

It strictly applies to the logical device abstraction in the SPI driver, however, each of these uses its own separate CS line and as such would normally map to a physically device as well. You could theoretically do your own CS handling using a standard GPIO and use the logical devices to do thread separation.

Funny that I found this post by coincidence, with basically the same question I asked a few months ago, though it was on github.
https://github.com/espressif/esp-idf/issues/5517
It's also a bit ironic, given that people prefer to post there than here since this forum seems mostly dead.
Like OP and I pointed out on the github issue, the docs are more confusing than helpful in this case, and should be changed.