ahci: SATA driver + FAT32 persistent disk mounted at /disk

- ahci.rs: polling AHCI on PCI class 1/6/1, bus mastering + ABAR map,
  port 0 up, IDENTIFY + READ/WRITE DMA EXT through one 4KiB DMA buffer
- fat.rs: BPB parse, whole-FAT RAM cache with write-back to both copies,
  LFN read/write, dirs, multi-cluster files, FSInfo free-count sync,
  space-padded dot entries ('..' = cluster 0 under root), fsck-clean
- fs.rs: /disk mount node + 24-slot ephemeral node pool; ls/cat/hexdump/
  echo/mkdir/touch/rm/edit all work on disk paths unchanged
- QEMU: explicit bus assignment (disk=ide.0, ESP=ide.1); the implicit
  fat:rw:esp drive was stealing AHCI port 0
- Debugged against QEMU source: header DW0 is CFL in bits 4:0 / PRDTL in
  bits 31:16 (Linux libahci layout), FIS count at bytes 12-13, device at
  byte 7; QEMU rejects H2D FIS flags bits 6:4, so direction is the
  header W bit only
- Verified: full shell round-trip on /disk, reboot persistence (poweroff
  then mdir/mtype and a fresh boot), fsck.fat clean

1 files changed, 5 insertions, 1 deletions

diff --git a/rsnix/src/gop.rs b/rsnix/src/gop.rs
index fa14eae..77cc514 100644
--- a/rsnix/src/gop.rs
+++ b/rsnix/src/gop.rs
@@ -167,7 +167,11 @@ impl Framebuffer {
             if SHADOW.is_null() {
                 // No shadow (allocation failed): fall back to shifting the
                 // display directly.
-                ptr::copy(self.base.add(n * row_bytes), self.base, total - n * row_bytes);
+                ptr::copy(
+                    self.base.add(n * row_bytes),
+                    self.base,
+                    total - n * row_bytes,
+                );
                 let last_row = self.base.add(total - n * row_bytes);
                 for i in 0..(n * row_words) {
                     ptr::write_volatile(last_row.add(i * 4) as *mut u32, self.bg);