[PATCH v2] rust/qemu-macros: Convert bit value to u8 within #[property]

[Zhao Liu <zhao1.liu@intel.com>]

For bit property, make the type conversion within the #[property] macro
so that users do not need to handle the conversion.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
Changes Since v2:
 - Check #field_ty::BITS instead of u8::MAX.
 - Update test cases.
---
 rust/hw/timer/hpet/src/device.rs |  2 +-
 rust/qemu-macros/src/lib.rs      | 23 ++++++++++++++++++-----
 rust/qemu-macros/src/tests.rs    | 15 ++++++++++++---
 3 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/rust/hw/timer/hpet/src/device.rs b/rust/hw/timer/hpet/src/device.rs
index 86638c076666..23f2eefd1cd9 100644
--- a/rust/hw/timer/hpet/src/device.rs
+++ b/rust/hw/timer/hpet/src/device.rs
@@ -539,7 +539,7 @@ pub struct HPETState {
     // Internal state
     /// Capabilities that QEMU HPET supports.
     /// bit 0: MSI (or FSB) support.
-    #[property(rename = "msi", bit = HPET_FLAG_MSI_SUPPORT_SHIFT as u8, default = false)]
+    #[property(rename = "msi", bit = HPET_FLAG_MSI_SUPPORT_SHIFT, default = false)]
     flags: u32,
 
     /// Offset of main counter relative to qemu clock.
diff --git a/rust/qemu-macros/src/lib.rs b/rust/qemu-macros/src/lib.rs
index 50239f228be2..ee417bb4b4ef 100644
--- a/rust/qemu-macros/src/lib.rs
+++ b/rust/qemu-macros/src/lib.rs
@@ -262,12 +262,25 @@ macro_rules! str_to_c_str {
             },
         )?;
         let field_ty = field.ty.clone();
-        let qdev_prop = if bitnr.is_none() {
-            quote! { <#field_ty as ::hwcore::QDevProp>::BASE_INFO }
+        let (qdev_prop, bitval) = if let Some(bitval) = bitnr {
+            (
+                quote! { <#field_ty as ::hwcore::QDevProp>::BIT_INFO },
+                quote! {
+                    {
+                        const {
+                            assert!(#bitval >= 0 && #bitval < #field_ty::BITS as _,
+                                    "bit number exceeds type bits range");
+                        }
+                        #bitval as u8
+                    }
+                },
+            )
         } else {
-            quote! { <#field_ty as ::hwcore::QDevProp>::BIT_INFO }
+            (
+                quote! { <#field_ty as ::hwcore::QDevProp>::BASE_INFO },
+                quote! { 0 },
+            )
         };
-        let bitnr = bitnr.unwrap_or(syn::Expr::Verbatim(quote! { 0 }));
         let set_default = defval.is_some();
         let defval = defval.unwrap_or(syn::Expr::Verbatim(quote! { 0 }));
         properties_expanded.push(quote! {
@@ -275,7 +288,7 @@ macro_rules! str_to_c_str {
                 name: ::std::ffi::CStr::as_ptr(#prop_name),
                 info: #qdev_prop,
                 offset: ::core::mem::offset_of!(#name, #field_name) as isize,
-                bitnr: #bitnr,
+                bitnr: #bitval,
                 set_default: #set_default,
                 defval: ::hwcore::bindings::Property__bindgen_ty_1 { u: #defval as u64 },
                 ..::common::Zeroable::ZERO
diff --git a/rust/qemu-macros/src/tests.rs b/rust/qemu-macros/src/tests.rs
index 65691412ff57..b65cf656fa36 100644
--- a/rust/qemu-macros/src/tests.rs
+++ b/rust/qemu-macros/src/tests.rs
@@ -179,7 +179,10 @@ unsafe impl ::hwcore::DevicePropertiesImpl for DummyState {
                         name: ::std::ffi::CStr::as_ptr(c"flags"),
                         info: <u32 as ::hwcore::QDevProp>::BIT_INFO,
                         offset: ::core::mem::offset_of!(DummyState, flags) as isize,
-                        bitnr: 3,
+                        bitnr : {
+                            const { assert!(3 >= 0 && 3 < u32::BITS as _ , "bit number exceeds type bits range"); }
+                            3 as u8
+                        },
                         set_default: false,
                         defval: ::hwcore::bindings::Property__bindgen_ty_1 { u: 0 as u64 },
                         ..::common::Zeroable::ZERO
@@ -207,7 +210,10 @@ unsafe impl ::hwcore::DevicePropertiesImpl for DummyState {
                         name: ::std::ffi::CStr::as_ptr(c"flags"),
                         info: <u32 as ::hwcore::QDevProp>::BIT_INFO,
                         offset: ::core::mem::offset_of!(DummyState, flags) as isize,
-                        bitnr: 3,
+                        bitnr : {
+                            const { assert!(3 >= 0 && 3 < u32::BITS as _ , "bit number exceeds type bits range"); }
+                            3 as u8
+                        },
                         set_default: true,
                         defval: ::hwcore::bindings::Property__bindgen_ty_1 { u: true as u64 },
                         ..::common::Zeroable::ZERO
@@ -235,7 +241,10 @@ unsafe impl ::hwcore::DevicePropertiesImpl for DummyState {
                         name: ::std::ffi::CStr::as_ptr(c"msi"),
                         info: <u64 as ::hwcore::QDevProp>::BIT_INFO,
                         offset: ::core::mem::offset_of!(DummyState, flags) as isize,
-                        bitnr: 3,
+                        bitnr : {
+                            const { assert!(3 >= 0 && 3 < u64::BITS as _ , "bit number exceeds type bits range"); }
+                            3 as u8
+                        },
                         set_default: true,
                         defval: ::hwcore::bindings::Property__bindgen_ty_1 { u: false as u64 },
                         ..::common::Zeroable::ZERO
-- 
2.34.1