mmio: Explicit read and write

Originally I thought that the compiler now reorders mmio accesses because
the output of the system-test was scrambled. However, this was not the
case. This is fixed in 178186b

Nevertheless, we put a lot of work into that and it is cleaner. So keep
that change.

Author: sysheap

kernel/src/drivers/virtio/capability.rs

@@ -1,3 +1,5 @@
+use crate::mmio_struct;
+
 // cfg_type values
 /* Common configuration */
 pub const VIRTIO_PCI_CAP_COMMON_CFG: u8 = 1;
@@ -19,35 +21,17 @@ pub const VIRTIO_PCI_CAP_SHARED_MEMORY_CFG: u8 = 8;
 #[allow(dead_code)]
 pub const VIRTIO_PCI_CAP_VENDOR_CFG: u8 = 9;
 
-#[allow(dead_code, non_camel_case_types)]
-#[derive(Debug)]
-#[repr(packed)]
-pub(super) struct virtio_pci_cap {
-    cap_vndr: u8,     /* Generic PCI field: PCI_CAP_ID_VNDR */
-    cap_next: u8,     /* Generic PCI field: next ptr. */
-    cap_len: u8,      /* Generic PCI field: capability length */
-    cfg_type: u8,     /* Identifies the structure. */
-    bar: u8,          /* Where to find it. */
-    id: u8,           /* Multiple capabilities of the same type */
-    padding: [u8; 2], /* Pad to full dword. */
-    offset: u32,      /* Offset within bar. */
-    length: u32,      /* Length of the structure, in bytes. */
-}
-
-impl virtio_pci_cap {
-    pub fn cfg_type(&self) -> u8 {
-        self.cfg_type
-    }
-
-    pub fn bar(&self) -> u8 {
-        self.bar
-    }
-
-    pub fn length(&self) -> u32 {
-        self.length
-    }
-
-    pub fn offset(&self) -> usize {
-        self.offset as usize
+mmio_struct! {
+    #[repr(packed)]
+    struct virtio_pci_cap {
+        cap_vndr: u8,     /* Generic PCI field: PCI_CAP_ID_VNDR */
+        cap_next: u8,     /* Generic PCI field: next ptr. */
+        cap_len: u8,      /* Generic PCI field: capability length */
+        cfg_type: u8,     /* Identifies the structure. */
+        bar: u8,          /* Where to find it. */
+        id: u8,           /* Multiple capabilities of the same type */
+        padding: [u8; 2], /* Pad to full dword. */
+        offset: u32,      /* Offset within bar. */
+        length: u32,      /* Length of the structure, in bytes. */
     }
 }