SIO2MAN Compatibility

SIO2MAN v1/v2 Compatibility for VMC, PADEMU, and MX4SIO

Problem Summary

PlayStation 2 games and IOP modules can register either or both sio2man export tables:

• sio2man v1 (0x100 family), where the second transfer entry is export #49.
• sio2man v2 (0x200 family), where the second transfer entry is export #51 and sio2_mtap_change_slot_set shifts later entries.
• PS2SDK sio2man, which registers both v1 (0x101) and v2 (0x201) tables so older and newer IOP modules can bind against the same driver.

Before this fix:

1. mcemu and pademu stored only one set of original sio2man function pointers (pSio2man25, pSio2man51, psio2_mc_transfer_init, psio2_transfer_reset). When a sio2man implementation registered both v1 and v2 export tables, hooking the second table overwrote the saved callbacks for the first table.
2. StartNow() and install_sio2hook() only looked up sio2man version 0x201. If a v1 table was already resident before hooks were installed, it was missed.
3. HookExportEntry() replaced only one slot in an export table. In sio2man tables where multiple export indices alias the same underlying routine (such as sio2_mc_transfer_init and sio2_pad_transfer_init, or sio2_transfer and sio2_transfer2 in ROM sio2man), callers importing the alias could bypass the hook or overwrite saved original pointers on repeated installation.
4. Sio2McEmu() always unlocked and relocked SIO2 through a single psio2_transfer_reset / psio2_mc_transfer_init pair instead of matching the sio2man version active for that transfer.
5. ee_core only preloaded PS2SDK sio2man when MX4SIO was active, not when VMC or PADEMU was active without MX4SIO.

Solution Overview

1. Preload PS2SDK sio2man for VMC, PADEMU, and MX4SIO

• src/platform/system.cpp now packs sio2man_irx (OPL_MODULE_ID_SIO2MAN) when CORE_IRX_MX4SIO, CORE_IRX_VMC, or PADEMU is active, except in native MMCE games.
• ee_core/src/iopmgr.c loads OPL_MODULE_ID_SIO2MAN in ResetIopSpecial() before the game-mode switch and before VMC (mcemu), PADEMU, or MX4SIO (mx4sio_bd) modules start.
• MMCE games use their own SIO2MAN: preloading the SDK copy can leave the in-game driver waiting on a lock. This follows original commit 11a5150e; its hardware A/B result does not establish migration console acceptance.
• OPL_MODULE_ID_MX4SIOBD is only started if OPL_MODULE_ID_SIO2MAN loaded cleanly (sio2manLoaded > 0).

2. Separate v1 and v2 Callback Storage and Wrappers

• modules/mcemu and modules/pademu now maintain two-element arrays ([0] for v1, [1] for v2) for:
  • pSio2man25[2]
  • pSio2man51[2]
  • psio2_mc_transfer_init[2] (mcemu)
  • psio2_transfer_reset[2] (mcemu)
• Dedicated wrapper callbacks (hookSio2McInit_1/_2, hookSio2man25_1/_2, hookSio2man51_1/_2, Sio2McEmu_1/_2) preserve the calling table version across the entire transfer lifecycle, including pademu_hookSio2man chaining and mc2_s1 direct DMA requests (temp_packet_version).

3. Alias-Safe and Idempotent Export Table Hooking

• HookExportEntry() in modules/mcemu/mcemu_sys.c and modules/pademu/sys_utils.c scans the full export table and replaces every slot that points to the same target function, returning the original target pointer.
• InstallSio2manHook() checks if (old != hookFn) before updating saved function pointers, preventing self-referential recursion if a table is hooked more than once or shares aliased entries.

4. Version-Matched Unlock/Lock Around VMC I/O

• Sio2McEmu(Sio2Packet *sd, int ver) calls sio2McUnlock(ver) before backing-store I/O and sio2McLock(ver) afterward, falling back to the opposite version slot (ver ^ 1) only if the primary slot is NULL.

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Source: docs/SIO2MAN-COMPATIBILITY.md @ b4c23bdac8f9.