DIP

System Menu disc detection

The Wii has a slot-loading drive, but the Disc Interface still calls its media state register and related commands "cover". Disc insertion and removal are reported through this interface.

The System Menu accesses the drive through /dev/di. To recognize an inserted disc and show its banner in the Disc Channel, it has to check the media state and read from the disc. For a Wii disc with update and game partitions, System Menu v513 makes these main requests:

1. Poll the cover register with ioctl 0x7A to detect the disc. Reading the status and acknowledging an interrupt are separate cover commands.
2. Request drive information with ioctl 0x12 and read the disc ID with ioctl 0x70.
3. Read disc metadata such as the partition table and region information with the unencrypted read ioctl 0x8D.
4. Open the update partition with ioctlv 0x8B, read from it with ioctl 0x71 then close it with ioctl 0x8C.
5. Open the game partition with ioctlv 0x8B and read from it with ioctl 0x71. These reads supply the data the System Menu uses to populate the Disc Channel and show its banner before the user selects Start.

Opening a partition returns its title metadata and makes it the target of subsequent partition reads. These reads must come from the currently open partition, not always from the game partition. Unencrypted reads take offsets relative to the start of the disc while partition reads take offsets into the open partition's decrypted data.

Drive-register initialization and cover interrupt handling are still required, but a cover status response alone does not supply the disc contents the Disc Channel needs.

Request dispatch

dvd_driver (0x2020062C) registers /dev/di. It passes ioctl arguments to di_ioctl (0x20200400) and vector arguments to di_ioctlv (0x20200284). After the handler returns, the driver passes its result to reply_request (0x20205E88).

Both argument structures begin at byte offset 0x0C in the IOS request. Each field is a 32 bit big endian value, and pointers are addresses in the driver's address space.

Each vector holds a 32 bit buffer pointer followed by a 32 bit length in bytes. Every ioctl except command 0x8E requires a 32 byte input buffer. Command 0x8B opens a partition and must be sent through ioctlv. Sending it through ioctl returns 0x20.

Cover commands

Disc cover handling

DIP accesses the Disc Interface cover register through virtual address 0x0D006004, mapped to physical address 0x0D806004.

DICVR - 0x0D006004 (32 bits)

wait_for_cover_close (0x20200B98) enables cover interrupts then waits on its message queue. It ignores messages of type 10 and processes interrupt messages of type 11. A cover interrupt ends the wait only when the reset delay has expired and Cover State is clear. The routine acknowledges the cover interrupt even when those conditions do not allow it to finish.

init_driver_events (0x20200074) registers IOS event 18 with the transaction queue, using a message whose first 32 bit word is 11. Both the cover wait and the drive command completion path receive messages from this queue.

enable_cover_interrupt (0x202009C0) reads DICVR, clears bits 2:1 in the value then sets bit 1 before writing it back. disable_cover_interrupt (0x202009D4) clears bits 2:1 in the read value before writing it back. Both avoid acknowledging an existing cover interrupt as a side effect of changing its enable. acknowledge_cover (0x202009B0) reads the register then writes the value with bit 2 set.

Status initialization

init_drive_registers (0x20200D1C) acknowledges any pending transfer-complete and device-error status before enabling the corresponding interrupts. It polls the transfer-complete interrupt enable until the bit reads back as set. It then enables the device-error interrupt and disables the cover interrupt. It also checks that both acknowledged status fields are clear.

DISR - 0x0D006000 (32 bits)

This virtual address maps to physical address 0x0D806000.

clear_device_error (0x20200B80) acknowledges the device error while preserving the interrupt enables.