Re: [PATCH V4 1/8] libgpiod: Add libgpiod-sys rust crate

[Kent Gibson <warthog618@gmail.com>]

On Tue, Aug 02, 2022 at 02:20:08PM +0530, Viresh Kumar wrote:
> On 01-08-22, 23:56, Kent Gibson wrote:
> > The Rust bindings themselves should be building against the local build
> > tree, so well known relative paths.
> 
> Right, when we build everything with "make" we better use the already
> built library. I agree.
> 
> > For users, require they have libgpiod installed and use pkg_config to
> > locate it?
> > 
> > Is that what you mean?
> 
> Since we need the latest APIs, we can't trust the packages provided by
> distributions for now. i.e. "apt-get install libgpiod-dev" won't
> install the latest stuff we need.
> 

For user builds with the Rust bindings you always require an appropriate
version of libgpiod to be already installed, or it is the users problem
to arrange that.
For the time being that means it needs to be built and installed from
source.  I don't see an alternative to that, or a problem with it.
In the longer term it will be provided by the packaging system for the
platform.

I may well be missing something, but I don't see the problem, at least
nothing that requires addressing.

Cheers,
Kent.

> The only other option to get it working in environments like
> rust-vmm-containers (which tests the vhost-device crate currently) is
> to build / install libgpiod first. As I have understood, people don't
> really like it there (Maintainers of rust-vmm-containers) as this will
> have further dependencies and require more tools.
> 
> I even tried to generate the libgpiod-sys bindings on the fly first,
> but it required more tooling and there were issues with Musl build
> specifically. They suggested to use prebuild bindings as a solution,
> which I have now.
> 
> What about we have two separate features:
> 
> - "default" one will be used with "make" and will use prebuild library.
> 
> - "generate" one will be used by user crates and we will build the
>   files there like it is done now.
> 
> > Else, how do other Rust crates wrapping dynamic C libraries do it?
> 
> I think for standard libraries that are stable, the -sys crates just
> contain the pre-built bindings and wrappers and expect the library to
> be already installed.
> 
> -- 
> viresh