From dc23d2f22cafeb6b97ba460789a834a6c586314d Mon Sep 17 00:00:00 2001
From: salmonik <salmonik@tuta.io>
Date: Fri, 31 Jul 2026 19:53:53 +0200
Subject: 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
---
 scripts/qemu.sh | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'scripts/qemu.sh')

diff --git a/scripts/qemu.sh b/scripts/qemu.sh
index b75bed4..123d9d0 100755
--- a/scripts/qemu.sh
+++ b/scripts/qemu.sh
@@ -40,7 +40,10 @@ while [ $# -gt 0 ]; do
 		;;
 	--image | -i)
 		_img_file="$(printf -- '-drive file=%s,format=raw,if=none,id=hd' "$2")"
-		DRIVE_ARGS=("$_img_file" '-device' 'ide-hd,drive=hd')
+		# Explicit buses: data disk -> ide.0 (port 0), ESP -> ide.1.
+		DRIVE_ARGS=("$_img_file" '-device' 'ide-hd,drive=hd,bus=ide.0' \
+			'-drive' 'file=fat:rw:esp,format=raw,if=none,id=esp' \
+			'-device' 'ide-hd,drive=esp,bus=ide.1')
 		shift 2
 		;;
 	--bios | -b)
-- 
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