rust: add module to convert between success/-errno and io::Result

It is a common convention in QEMU to return a positive value in case of
success, and a negated errno value in case of error.  Unfortunately,
using errno portably in Rust is a bit complicated; on Unix the errno
values are supported natively by io::Error, but on Windows they are not;
so, use the libc crate.

This is a set of utility functions that are used by both chardev and
block layer bindings.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/rust/qemu-api/src/prelude.rs b/rust/qemu-api/src/prelude.rs
index fbf0ee23e0..634acf37a8 100644
--- a/rust/qemu-api/src/prelude.rs
+++ b/rust/qemu-api/src/prelude.rs
@@ -9,6 +9,8 @@ pub use crate::bitops::IntegerExt;
 pub use crate::cell::BqlCell;
 pub use crate::cell::BqlRefCell;
 
+pub use crate::errno;
+
 pub use crate::qdev::DeviceMethods;
 
 pub use crate::qom::InterfaceType;