firmware_loader: annotate doctests as no_run

The doctests of `Firmware` are compile-time only tests, since they
require a proper `Device` and a valid path to a (firmware) blob in order
to do something sane on runtime - we can't satisfy both of those
requirements.

Hence, configure the example as `no_run`.

Unfortunately, the kernel's Rust build system can't consider the
`no_run` attribute yet. Hence, for the meantime, wrap the example code
into a new function and never actually call it.

Fixes: de65828 ("rust: add firmware abstractions")
Signed-off-by: Danilo Krummrich <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: dakr

rust/kernel/firmware.rs

@@ -26,14 +26,18 @@ type FwFunc =
 ///
 /// # Examples
 ///
-/// ```
+/// ```no_run
 /// # use kernel::{c_str, device::Device, firmware::Firmware};
 ///
+/// # fn no_run() -> Result<(), Error> {
 /// # // SAFETY: *NOT* safe, just for the example to get an `ARef<Device>` instance
 /// # let dev = unsafe { Device::from_raw(core::ptr::null_mut()) };
 ///
-/// let fw = Firmware::request(c_str!("path/to/firmware.bin"), &dev).unwrap();
+/// let fw = Firmware::request(c_str!("path/to/firmware.bin"), &dev)?;
 /// let blob = fw.data();
+///
+/// # Ok(())
+/// # }
 /// ```
 pub struct Firmware(NonNull<bindings::firmware>);