docs(inventory): decompiled (Ghidra) read path; bottoms out at int 0x84/0xd2 services

2026-07-06 23:20:56 +01:00
parent 961526b545
commit 038c38f029
1 changed files with 31 additions and 0 deletions
@@ -183,6 +183,37 @@ explain why every raw `WL2:D` read returned no data — wrong paradigm.
 trigger the laser and a good decode (green LED). Only *retrieving* the decoded
 bytes is unsolved.

+### Decompilation (Ghidra) — the read path
+
+`SCANNER.DYL`/`SCANAPP` decompile cleanly in Ghidra (16-bit real-mode x86). The
+app-level read routine (`FUN_858d`) is:
+
+```c
+obj->flags |= 8;
+obj->[0x190] = 0;
+FUN_8ce8(); FUN_8cd3(); FUN_8cd3();       // pre-read setup
+obj->[0x194] = FUN_8d8e();                // acquire a read handle  (int 0x84)
+obj->[0x192] = FUN_8c8b(0,2,1,obj);       // set up the read buffer (int 0x84; int 0xd2)
+swi(0xcf)(); swi(0xcf)();                 // config / enable ops on the channel
+if (obj->[0x196] == 0)
+    obj->[0x196] = swi(0xcf)();           // P_FREAD -> decoded result stored at +0x196
+else
+    swi(0xcf)();                          // P_FCANCEL
+```
+
+The decoder-side helpers also decompile clearly: `FUN_7ae3` is the per-decoder
+init (dispatch on `[channel+10]`; case 4 = the Symbol path, which calls
+`FUN_6dc4` to build the `0xff 0xee …` command frame and writes the 11-byte param
+block); `FUN_7aa4` is the trigger (two `int 0xCF` ops = the `6`/`7` we use).
+
+**Remaining dependency:** the read acquires its handle and buffer through two
+further OS services — **`int 0x84`** (handle/manager service, sub-function in
+`AH`) and **`int 0xd2`** — and is woven into the app's object layout
+(`obj+0x190..0x196`). Reproducing it in C needs those two services mapped (their
+C wrappers / semantics) and the object fields understood. That is the next RE
+target; Ghidra makes it tractable but it is still several layers, and any result
+must be validated on the physical device (MAME cannot inject a scan).
+
 To close it, one of:
 1. The **Workabout MX C SDK** `SCANNER.DYL` header / OO category definition (what
   `SCANAPP` was built against) — the clean answer, and likely the only practical