Peripheral definitions in cortex-m are not `Send`, while those from `svd2rust` generated crates are

[codyps]

Comparing something like:

• stm32f103xx::TIM6
• cortex_m::ITM

Notably:

• Send is omitted from cortex_m::ITM
• mutable access (in the form of ptr() -> *mut RegisterBlock and DerefMut are removed from stm32f103xx::TIM6

I ran into this while trying to pass around ITM in cortex_m_rtfm, which wants Send on resources:

error[E0277]: the trait bound `*const (): core::marker::Send` is not satisfied in `cortex_m::peripheral::ITM`
  --> src/main.rs:16:1
   |
16 | / app! {
17 | |     device: stm32f429,
18 | |
19 | |     resources: {
...  |
29 | |     },
30 | | }
   | |_^ `*const ()` cannot be sent between threads safely
   |
   = help: within `cortex_m::peripheral::ITM`, the trait `core::marker::Send` is not implemented for `*const ()`
   = note: required because it appears within the type `core::marker::PhantomData<*const ()>`
   = note: required because it appears within the type `cortex_m::peripheral::ITM`

I've used a quick wrapper to workaround:

...
use core::ops::{Deref,DerefMut};
pub struct ITM(cortex_m::peripheral::ITM);

impl Deref for ITM {
    type Target = cortex_m::peripheral::ITM;
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for ITM {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}
unsafe impl Send for ITM {}

...
app! {
...
    resources: {
        static R_ITM: ITM;
        ...
    },

    tasks: {
        TIM7: {
            path: periodic,
            resources: [R_ITM, ...],
        },
    },
}

...
fn init(mut p: init::Peripherals) -> init::LateResources {
    ...

    init::LateResources {
        R_ITM: ITM(p.core.ITM),
        R_TIM7: tim,
    }
}

...

[japaric]

Send is omitted from cortex_m::ITM

Whoops. All the peripherals should implement Send in this crate; that was my omission. I'll cook up a PR.

[japaric]

v0.4.2 which contains the fix for this has been published