Must call dwt_initialise() before dwt_checkidlerc() to avoid segfault?

Wireless Connectivity Ultra-Wideband
1

The rx examples generally have this initialisation sequence:

  1. Set SPI rate.
  2. Power on/reset IC.
  3. dwt_probe()
  4. Poll dwt_checkidlerc()
  5. dwt_initialise()

See for example, simple_rx_nlos.c or rx_diagnostics.c.

In my experience (stm32) this reliably segfaults due to a read from a NULL pointer. And this seems entirely reasonable, since dwt_checkidlerc() calls this chain:

  • dwt_checkidlerc() in deca_compat.c
    • ioctl(DWT_CHECKIDLERC) in dw3000_device.c
      • ull_checkidlerc()
        • dwt_read16bitoffsetreg()
          • dwt_readfromdevice()
            • dwt_xfer3xxx(DW3000_SPI_RD_BIT)

And there, inside the DW3000_SPI_RD_BIT case, is this line:

if ((LOCAL_DATA(dw)->spicrc == DWT_SPI_CRC_MODE_WRRD) ...

LOCAL_DATA(dw) expands to dw->priv and priv is set to NULL in dwt_probe() when static_dw is assigned to dw. So this bombs out reliably.

The first thing dwt_initialise() does is malloc() this field, so calling it before dwt_checkidlerc() resolves the issue.

This seems pretty fundamental so I’m surprised I can find no discussion or explanation. Is my version of the API hosed? Am I using it wrong? Or is everyone quietly doing this as well?