rust: factory: Add rros_release_element function

[yexuanyang]

Diff:

1. In factory.rs:

• Change the field inside and dispose in struct RrosFactory.
• Implement methods remove_element_device, is_public, __do_put_element, do_put_element_work, do_put_element_irq, do_put_element, put_element for RrosElement
• Modify the code used inside, because type has changed from Option<RrosFactoryInside> to RrosFactoryInside.
• Add function unbind_file_to_element
• Add function rros_open_element and rros_release_element

2. In sub factory(proxy/buf/poll,etc. .rs): Change the static factory creation.
3. In device.rs: Implement unregister for Device
4. In type.rs: Implement hash_del for HlistNode

Status:

1. Compilation: Compile with clang-13.0.1 toolchain, ARCH=arm64, use rros_defconfig.
2. Functional test: Haven't started yet.

Related issue:
resolving #47

[yexuanyang]

Status:

1. Compilation: Compile with clang-13.0.1 toolchain, ARCH=arm64, use rros_defconfig.

The compilation finishes with 13 warnings. All of them are about never used.

[ruiqurm]

Thanks for your contribution!
Overall, IMO it's better to use MaybeUninit inside the factory if we like C-style initialization.And we can use a factoryBuilder when initializing the factory. However, It seems that it needs a lot of designs and maybe we can put this schedule in the next refactoring.

[ruiqurm]

Why running_inband().is_err() instead of something like running_oob()? It's a little confusing

[ruiqurm]

You can use the built-in function unlikely if this condition rare happens.

[yexuanyang]

Why running_inband().is_err() instead of something like running_oob()? It's a little confusing

I don't find the function running_oob in our kernel. I can implement it and use it there.

[yexuanyang]

You can use the built-in function unlikely if this condition rare happens.

Thanks for your tips, using core::intrinsics::unlikely is better, it is already been added in core crate at rust-for-linux, I didn't know it before.

[ruiqurm]

Yes. I mean the API of running_inband here is very strange.

pub fn running_inband() -> Result<usize> {
    let res = unsafe { rust_helper_running_inband() };
    if res == 1 {
        return Ok(0);
    }
    Err(Error::EINVAL)
}

I search for the running_inband method:

static __always_inline bool running_inband(void)
{
	return stage_level() == 0;
}

static __always_inline bool running_oob(void)
{
	return !running_inband();
}

I think we don not have to handle the error and just return true or false is ok.

[yexuanyang]

Yes. I mean the API of running_inband here is very strange.

pub fn running_inband() -> Result<usize> {
    let res = unsafe { rust_helper_running_inband() };
    if res == 1 {
        return Ok(0);
    }
    Err(Error::EINVAL)
}

I search for the running_inband method:

static __always_inline bool running_inband(void)
{
	return stage_level() == 0;
}

static __always_inline bool running_oob(void)
{
	return !running_inband();
}

I think we don not have to handle the error and just return true or false is ok.

Ok, I will change the running_inband function and related code.

[yexuanyang]

Currently, there are a lot of codes that use running_inband().is_ok/err() to determine the current stage, so I think it would be more appropriate to create a new issue and modify this function later.
@ruiqurm

[ruiqurm]

Should we add a comment here? It's a little weird that you get the data inside but do not want to use it.

[yexuanyang]

Do you mean fac hasn't been used? I call the method dispose in fac.

[ruiqurm]

No. I mean it seems that the dispose is a read-only field, which does not need to be guarded by the lock?

[ruiqurm]

I think the issue is concerned with initialization. If the dispose is set at the initialization, there is no need to guard it?

[ruiqurm]

Just an advice. Can we require the subsystem to set a dispose method at compile time like that in C? I am not sure if it is difficult to implement currently.

[ruiqurm]

Is dispose a mandatory field? Maybe we should provide a way to let every subsystem pass its function pointer at initialization?

[yexuanyang]

It is now Option<fn(&mut RrosElement)>, subsystems can change the fn inside at the factory initialization.