rust-sysfs-pwm

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thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Io(Os { code: 2, kind: NotFound, message: "No such file or directory" })', src/libcore/result.rs:999:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:477
   7: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:384
   8: rust_begin_unwind
             at src/libstd/panicking.rs:311
   9: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  10: core::result::unwrap_failed
             at /rustc/eae3437dfe991621e8afdc82734f4a172d7ddf9b/src/libcore/macros.rs:18
  11: core::result::Result<T,E>::unwrap
             at /rustc/eae3437dfe991621e8afdc82734f4a172d7ddf9b/src/libcore/result.rs:800
  12: cucaracha::pwmled::PwmLed::new
             at src/pwmled.rs:40
  13: cucaracha::main
             at src/main.rs:22
  14: std::rt::lang_start::{{closure}}
             at /rustc/eae3437dfe991621e8afdc82734f4a172d7ddf9b/src/libstd/rt.rs:64
  15: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:49
  16: std::panicking::try::do_call
             at src/libstd/panicking.rs:296
  17: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:82
  18: std::panicking::try
             at src/libstd/panicking.rs:275
  19: std::panic::catch_unwind
             at src/libstd/panic.rs:394
  20: std::rt::lang_start_internal
             at src/libstd/rt.rs:48
  21: std::rt::lang_start
             at /rustc/eae3437dfe991621e8afdc82734f4a172d7ddf9b/src/libstd/rt.rs:64
  22: main
  23: __libc_start_main

because the crate is trying to get /sys/class/pwm/pwmchip{}/pwm{}/{} where on my beaglebone it's /sys/class/pwm/pwmchip4/pwm-4\:0/

The line in my code causing this is pwm.enable(true).unwrap();

fn pwm_file_wo(chip: &PwmChip, pin: u32, name: &str) -> Result<File> {
    let f = OpenOptions::new().write(true).open(format!(
        "/sys/class/pwm/pwmchip{}/pwm{}/{}",
        chip.number, pin, name
    ));
    if !f.is_ok() {
        let f = OpenOptions::new().write(true).open(format!(
            "/sys/class/pwm/pwmchip{}/pwm-{}:{}/{}",
            chip.number, chip.number, pin, name
        ))?;
        return Ok(f);
    }
    Ok(f.unwrap())
}

is working.

Also

format!(
            "/sys/class/pwm/pwm-{}:{}/{}", chip.number, pin, name
        )

Not sure how to actually detect if you will get one pwm{} or pwm-{}:{}.

If you want my quick fix, I can do a PR.