vfio-bindings: Update CONTRIBUTING.md

Document how to regenerate `vfio_bindings` from linux source.

Signed-off-by: Ruoqing He <[email protected]>

Author: RuoqingHe

vfio-bindings/CONTRIBUTING.md

@@ -24,41 +24,22 @@ For this example we assume that you have both linux and vfio-bindings
 repositories in your root and we will use linux version v5.2 as example.
 
 ```bash
-# Step 1: Crate a new module using a name with format "bindings_vVERSION" in
-# src/
-cd vfio-bindings
-mkdir src/bindings_v5_2_0
-cd ~
-
-# Step 2: Copy the "mod.rs" file from the directory of an already existing
-# version module to the one we've just created.
-cd vfio-bindings/src
-cp bindings_v5_0_0/mod.rs bindings_v5_2_0/mod.rs
-
-# linux is the repository that you cloned at the previous step.
+# linux is the repository that you cloned previously.
 cd linux
 
-# Step 3: Checkout the version you want to generate the bindings for.
+# Step 1: Checkout the version you want to generate the bindings for.
 git checkout v5.2
 
-# Step 4: Generate the bindings from the kernel headers.
-make headers_install INSTALL_HDR_PATH=v5_2_headers
-cd v5_2_headers
+# Step 2: Generate the bindings from the kernel headers.
+make headers_install INSTALL_HDR_PATH=vfio_headers
+cd vfio_headers
 bindgen include/linux/vfio.h -o vfio.rs \
     --impl-debug --with-derive-default  \
     --with-derive-partialeq  --impl-partialeq \
     -- -Iinclude
 
 cd ~
 
-# Step 5: Copy the generated files to the new version module.
-cp linux/v5_2_headers/vfio.rs vfio-bindings/src/bindings_v5_2_0
-```
-Finally add the new version module to `vfio-bindings/lib.rs`. If this version
-is newer than the others already present, make this version the default one by
-getting it imported when there isn't any other version specified as a feature:
-
-```rust
-#[cfg(all(not(feature = "vfio-v5_0_0"), not(feature = "vfio-v5_2_0")))]
-pub use super::bindings_v5_2_0::*;
+# Step 3: Copy the generated files to the new version module.
+cp linux/vfio_headers/vfio.rs vfio-bindings/src/vfio_bindings
 ```