WithPwm trait should be public

[Fomys]

I writing a generic struct that takes a pwm channel to control a motor.

We've tried this code:

struct Motor<TIM: TimerExt, const C: u8> {
    pwm: PwmChannel<TIM, C>,
}

And I get the following error:

error[E0599]: the method `get_max_duty` exists for struct `PwmChannel<TIM, C>`, but its trait bounds were not satisfied
  --> base-roulante/src/main.rs:64:73
   |
64 |         let consigne = pid_correction / Self::MAX_CORRECTION * self.pwm.get_max_duty();
   |                                                                         ^^^^^^^^^^^^ method cannot be called on `PwmChannel<TIM, C>` due to unsatisfied trait bounds
   |
  ::: /home/fomys/.cargo/registry/src/github.com-1ecc6299db9ec823/stm32f1xx-hal-0.9.0/src/timer/pwm.rs:89:1
   |
89 | pub struct PwmChannel<TIM, const C: u8> {
   | --------------------------------------- doesn't satisfy `PwmChannel<TIM, C>: PwmPin`
   |
   = note: the following trait bounds were not satisfied:
           `TIM: stm32f1xx_hal::timer::sealed::WithPwm`
           `TIM: stm32f1xx_hal::timer::sealed::WithPwm`
           which is required by `PwmChannel<TIM, C>: PwmPin`

The ideal resolution would be to add trait bound with WithPwm trait, but it's impossible as it's a sealed trait.

Shouldn't it be public in order write this trait bound ? If this isn't the case, how should I resolve ?

[burrbull]

Yeah. Generic code with sealed trait is often problematic. As fast fix you could use get_max_duty from PwmPin: https://github.com/stm32-rs/stm32f1xx-hal/blob/f9b24f4d9bac7fc3c93764bd295125800944f53b/src/timer/hal_02.rs#L136

[Fomys]

To use PwmPin I have to add the trait bound PwmPin<Duty = u16> as the Duty is also generic. Should I make a PR to make WithPwm public ?