Why does to_result() in libtock-rs/platform/src/command_return.rs return BADRVAL for a driver check?

[potto216]

When performing a driver check with Console, Alarm, etc .is_success() and .raw_values()
return correct values but I don't understand .to_result()'s meaning

The three methods are located in libtock-rs/apis/console/src/lib.rs

For example for Console

S::command(DRIVER_NUM, command::DRIVER_CHECK, 0, 0).is_success()

returns true

and

S::command(DRIVER_NUM, command::DRIVER_CHECK, 0, 0).raw_values()
returns
ReturnVariant(128), r1 = 0, r2 = 0, r3 = 0
where pub const SUCCESS: ReturnVariant = ReturnVariant(128);

But
S::command(DRIVER_NUM, command::DRIVER_CHECK, 0, 0).to_result()

returns
BADRVAL

Is this expected? I would think this is indicating an error.

[hudson-ayers]

Agreed that is not expected. The docs for to_result() recommend using type ascription to make the types for to_result() explicit at the call site -- I suspect that the type for T is being inferred incorrectly leading to the return value you see. I recommend trying let res: Result<(), ErrorCode> = S::command(...).to_result();

[potto216]

Okay thanks, I'll investigate that this week.

[potto216]

@hudson-ayers your suggestion worked. In libtock-rs/apis/console/src/lib.rs
changing

    #[inline(always)]
    pub fn driver_check_result() -> Result<u32, ErrorCode> {
        S::command(DRIVER_NUM, command::DRIVER_CHECK, 0, 0).to_result()
    }

to

    #[inline(always)]
    pub fn driver_check_result() -> Result<(), ErrorCode> {
        let res: Result<(), ErrorCode> =
            S::command(DRIVER_NUM, command::DRIVER_CHECK, 0, 0).to_result();
        res
    }

Worked. Isn't the return value Result<u32, ErrorCode> wrong for command::DRIVER_CHECK since return_variant::SUCCESS_U32 is defined as 129 instead of return_variant::SUCCESS which is defined as 128 and associated with

impl SuccessData for () {
    const RETURN_VARIANT: ReturnVariant = return_variant::SUCCESS; //defined as 128 (pub const SUCCESS: ReturnVariant = ReturnVariant(128);)
}

This is what the console driver check returns: 0 => Ok(()),

Therefore driver_check_result's return value Result<u32, ErrorCode> should be changed to Result<(), ErrorCode> to match what the capsule's driver check is actually returning. If the analysis is correct and this is a bug I can file an issue and submit a PR.

[hudson-ayers]

I agree with your analysis, please submit a PR

[potto216]

See #446