HAL-Bus SPI Exclusive Device Unsatisfied Traits

Reproduce the failure from examples/tiva-c-connected-launchpad/examples/spi_hello.rs, then inspect embedded-hal-bus-0.1.0/src/spi/exclusive.rs and the tm4c129x_hal SPI implementation. Trace the required blocking SPI Write and Default trait bounds and compare them with the HAL's implemented traits. Done means identifying which component causes the mismatch and documenting or correcting the compatible trait usage.

Good morning,

I am trying to understand if the unsatisfied traits error I am receiving in my implementation is due to an error in my implementation, the platform HAL package, or the underlying embedded HAL code.

I am trying to use the embedded_hal_bus ExclusiveDevice struct to wrap an SPI bus into an SPI device.

The SPI bus I have initialised using the platform HAL package (tm4c129x_hal):

let mut spi0 = hal::spi::Spi::spi0(
    p.SSI0,
    (
        porta
            .pa2
            .into_af_push_pull::<hal::gpio::AF15>(&mut porta.control),
        porta
            .pa5
            .into_af_push_pull::<hal::gpio::AF15>(&mut porta.control),
        porta
            .pa4
            .into_af_push_pull::<hal::gpio::AF15>(&mut porta.control),
    ),
    hal::spi::MODE_0,
    1_u32.mhz(),
    &clocks,
    &sc.power_control,
);

I'm then wrapping that up in the ExclusiveDevice object (cs0 is just a normal GPIO pin in output mode).

let mut spi0_dev0 = ExclusiveDevice::new_no_delay(
    &spi0, cs0
);

However, this won't compile when I try to use the write() method of the ExlusiveDevice object. (message is a Vec of bytes).

error[E0599]: the method `write` exists for struct `ExclusiveDevice<&Spi<SSI0, (PA2<AlternateFunction<AF15, ...>>, ..., ...)>, ..., ...>`, but its trait bounds were not satisfied
  --> examples/tiva-c-connected-launchpad/examples/spi_hello.rs:67:27
   |
67 |         let _ = spi0_dev0.write(message);
   |                           ^^^^^ method cannot be called due to unsatisfied trait bounds
   |
  ::: /home/***/.cargo/registry/src/index.crates.io-6f17d22bba15001f/embedded-hal-bus-0.1.0/src/spi/exclusive.rs:19:1
   |
19 | pub struct ExclusiveDevice<BUS, CS, D> {
   | --------------------------------------
   | |
   | doesn't satisfy `_: Default<_>`
   | doesn't satisfy `_: _embedded_hal_blocking_spi_Write<_>`
   |
   = note: the full type name has been written to '.../target/thumbv7em-none-eabihf/debug/examples/spi_hello-b9cc2dd24018ba0e.long-type-5094367532974101285.txt'
   = note: the following trait bounds were not satisfied:
           `ExclusiveDevice<&tm4c129x_hal::spi::Spi<tm4c129x_hal::tm4c129x::SSI0, (PA2<AlternateFunction<AF15, PushPull>>, PA5<AlternateFunction<AF15, PushPull>>, PA4<AlternateFunction<AF15, PushPull>>)>, PA6<Output<PushPull>>, NoDelay>: embedded_hal::blocking::spi::write::Default<_>`
           which is required by `ExclusiveDevice<&tm4c129x_hal::spi::Spi<tm4c129x_hal::tm4c129x::SSI0, (PA2<AlternateFunction<AF15, PushPull>>, PA5<AlternateFunction<AF15, PushPull>>, PA4<AlternateFunction<AF15, PushPull>>)>, PA6<Output<PushPull>>, NoDelay>: tm4c129x_hal::prelude::_embedded_hal_blocking_spi_Write<_>`

What I can't work out is what needs to be changed so that the trait bounds are satisfied. Can anyone shed some light?