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

[Viresh Kumar <viresh.kumar@linaro.org>]

This adds libgpiod-sys rust crate, which provides FFI (foreign function
interface) bindings for libgpiod APIs.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 .gitignore                            |  5 ++
 bindings/rust/libgpiod-sys/Cargo.toml | 15 ++++++
 bindings/rust/libgpiod-sys/build.rs   | 69 +++++++++++++++++++++++++++
 bindings/rust/libgpiod-sys/src/lib.rs | 20 ++++++++
 bindings/rust/libgpiod-sys/wrapper.h  |  2 +
 5 files changed, 111 insertions(+)
 create mode 100644 bindings/rust/libgpiod-sys/Cargo.toml
 create mode 100644 bindings/rust/libgpiod-sys/build.rs
 create mode 100644 bindings/rust/libgpiod-sys/src/lib.rs
 create mode 100644 bindings/rust/libgpiod-sys/wrapper.h

diff --git a/.gitignore b/.gitignore
index 58e1c5fc7e00..9541482d5efb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,3 +33,8 @@ stamp-h1
 # profiling
 *.gcda
 *.gcno
+
+# Added by cargo
+
+target
+Cargo.lock
diff --git a/bindings/rust/libgpiod-sys/Cargo.toml b/bindings/rust/libgpiod-sys/Cargo.toml
new file mode 100644
index 000000000000..77f82719d269
--- /dev/null
+++ b/bindings/rust/libgpiod-sys/Cargo.toml
@@ -0,0 +1,15 @@
+[package]
+name = "libgpiod-sys"
+version = "0.1.0"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+
+[features]
+generate = [ "bindgen" ]
+
+[build-dependencies]
+bindgen = { version = "0.59.1", optional = true }
+cc = "1.0.46"
diff --git a/bindings/rust/libgpiod-sys/build.rs b/bindings/rust/libgpiod-sys/build.rs
new file mode 100644
index 000000000000..bbcd30f79d23
--- /dev/null
+++ b/bindings/rust/libgpiod-sys/build.rs
@@ -0,0 +1,69 @@
+#[cfg(feature = "generate")]
+extern crate bindgen;
+#[cfg(feature = "generate")]
+use std::env;
+#[cfg(feature = "generate")]
+use std::path::PathBuf;
+
+#[cfg(feature = "generate")]
+fn generate_bindings(files: &Vec<&str>) {
+    // Tell cargo to invalidate the built crate whenever following files change
+    println!("cargo:rerun-if-changed=wrapper.h");
+
+    for file in files {
+        println!("cargo:rerun-if-changed={}", file);
+    }
+
+    // The bindgen::Builder is the main entry point
+    // to bindgen, and lets you build up options for
+    // the resulting bindings.
+    let bindings = bindgen::Builder::default()
+        // The input header we would like to generate
+        // bindings for.
+        .header("wrapper.h")
+        // Tell cargo to invalidate the built crate whenever any of the
+        // included header files changed.
+        .parse_callbacks(Box::new(bindgen::CargoCallbacks))
+        // Finish the builder and generate the bindings.
+        .generate()
+        // Unwrap the Result and panic on failure.
+        .expect("Unable to generate bindings");
+
+    // Write the bindings to the $OUT_DIR/bindings.rs file.
+    let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
+    bindings
+        .write_to_file(out_path.join("bindings.rs"))
+        .expect("Couldn't write bindings!");
+}
+
+fn build_gpiod(files: Vec<&str>) {
+    // Tell Cargo that if the given file changes, to rerun this build script.
+    println!("cargo:rerun-if-changed=../../../lib/");
+
+    // Use the `cc` crate to build a C file and statically link it.
+    cc::Build::new()
+        .files(files)
+        .define("_GNU_SOURCE", None)
+        .define("GPIOD_VERSION_STR", "\"libgpio-sys\"")
+        .include("../../../include")
+        .compile("gpiod");
+}
+
+fn main() {
+    let files = vec![
+        "../../../lib/chip.c",
+        "../../../lib/chip-info.c",
+        "../../../lib/edge-event.c",
+        "../../../lib/info-event.c",
+        "../../../lib/internal.c",
+        "../../../lib/line-config.c",
+        "../../../lib/line-info.c",
+        "../../../lib/line-request.c",
+        "../../../lib/misc.c",
+        "../../../lib/request-config.c",
+    ];
+
+    #[cfg(feature = "generate")]
+    generate_bindings(&files);
+    build_gpiod(files);
+}
diff --git a/bindings/rust/libgpiod-sys/src/lib.rs b/bindings/rust/libgpiod-sys/src/lib.rs
new file mode 100644
index 000000000000..3384863a567c
--- /dev/null
+++ b/bindings/rust/libgpiod-sys/src/lib.rs
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#[allow(
+    clippy::all,
+    deref_nullptr,
+    dead_code,
+    non_camel_case_types,
+    non_upper_case_globals,
+    non_snake_case,
+    improper_ctypes
+)]
+
+mod bindings_raw {
+    #[cfg(feature = "generate")]
+    include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
+
+    #[cfg(not(feature = "generate"))]
+    include!("bindings.rs");
+}
+pub use bindings_raw::*;
diff --git a/bindings/rust/libgpiod-sys/wrapper.h b/bindings/rust/libgpiod-sys/wrapper.h
new file mode 100644
index 000000000000..7bc1158b7d90
--- /dev/null
+++ b/bindings/rust/libgpiod-sys/wrapper.h
@@ -0,0 +1,2 @@
+#include <string.h>
+#include "../../../include/gpiod.h"
-- 
2.31.1.272.g89b43f80a514