[PATCH 8/9] rust: error: expose EPROTO

Add the named protocol-error constant so Rust protocol drivers
can return the same specific errno as their C counterparts without
constructing it from a raw integer.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Mike Lothian <[email protected]>
---
 rust/kernel/error.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index a56ba6309594..9492471c2677 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -64,6 +64,7 @@ macro_rules! declare_err {
     declare_err!(EPIPE, "Broken pipe.");
     declare_err!(EDOM, "Math argument out of domain of func.");
     declare_err!(ERANGE, "Math result not representable.");
+    declare_err!(EPROTO, "Protocol error.");
     declare_err!(EOVERFLOW, "Value too large for defined data type.");
     declare_err!(EMSGSIZE, "Message too long.");
     declare_err!(ETIMEDOUT, "Connection timed out.");