From 057e5377af2d086917b9cd0ffb336231d7d098cb Mon Sep 17 00:00:00 2001
From: user <user@clank>
Date: Thu, 16 Jul 2026 11:42:38 +0200
Subject: fs rewrite stage 1: persistent block device (bounce buffer, cart
 SRAM)

- blk.asm: read_block/write_block move 256-byte blocks between battery-backed
  cart-RAM banks (8-11, the 'disk') and a WRAM bounce buffer. Banking is hidden
  in those two routines; they inline the 'restore my bank' step so they never
  touch the stack while the disk bank is mapped over the process's $A000 window
  (the stack lives there too -- a call/ret would rug-pull it).
- format-on-first-boot: superblock magic in block 0; otherwise the disk persists.
- cart RAM bumped to 128 KiB (-r 4); process banks 0-7, disk banks 8-11.
- debug tool 'blk fill/peek' + syscalls to validate round-trip and persistence.
- verified: round-trip incl. cross-bank (block 100 -> bank 11); block survives a
  reboot via .sav; magic intact (no reformat on 2nd boot).
- old WRAM 8-slot FS still backs the tools until stages 2-3.
---
 c/blk.c  | 13 +++++++++++++
 c/gbos.h |  2 ++
 c/libc.s | 14 ++++++++++++++
 3 files changed, 29 insertions(+)
 create mode 100644 c/blk.c

(limited to 'c')

diff --git a/c/blk.c b/c/blk.c
new file mode 100644
index 0000000..adf2a58
--- /dev/null
+++ b/c/blk.c
@@ -0,0 +1,13 @@
+#include "gbos.h"
+/* blk: exercise the block device.  blk fill <n> <v>   |   blk peek <n> */
+void main(void) {
+    char *argv[4];
+    unsigned char argc = argv_parse(argv, 4);
+    if (argc >= 3 && argv[0][0] == 'f') {
+        bfill(atou(argv[1]), atou(argv[2]));
+    } else if (argc >= 2 && argv[0][0] == 'p') {
+        putu(bpeek(atou(argv[1]))); nl();
+    } else {
+        puts("usage: blk fill <n> <v> | blk peek <n>"); nl();
+    }
+}
diff --git a/c/gbos.h b/c/gbos.h
index f76d1e0..03a91de 100644
--- a/c/gbos.h
+++ b/c/gbos.h
@@ -43,4 +43,6 @@ unsigned char psget(unsigned char slot, unsigned char *buf); /* {pid,state,prog}
 void          progname(unsigned char id, char *buf);         /* id -> name     */
 void          yield(void);
 unsigned char reap(void);                   /* reap a finished bg job, or 0   */
+void          bfill(unsigned char block, unsigned char byte); /* [debug] disk */
+unsigned char bpeek(unsigned char block);                     /* [debug] disk */
 #endif
diff --git a/c/libc.s b/c/libc.s
index 2e2516b..5b81dca 100644
--- a/c/libc.s
+++ b/c/libc.s
@@ -199,3 +199,17 @@ _reap:
 	ld	c, #22			; SYS_REAP
 	rst	#0x30
 	ret
+
+	.globl _bfill, _bpeek
+	;; void bfill(unsigned char block /*A*/, unsigned char byte /*E*/)
+_bfill:
+	ld	b, a
+	ld	c, #23			; SYS_BFILL
+	rst	#0x30
+	ret
+	;; unsigned char bpeek(unsigned char block /*A*/) -> A
+_bpeek:
+	ld	b, a
+	ld	c, #24			; SYS_BPEEK
+	rst	#0x30
+	ret
-- 
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