EHCI

Service startup

The EHCI module in IOS58 provides /dev/usb/ehc. ehci_worker (0x138C0E90) creates a 64 message queue and registers the device before calling init_ehci (0x138C1624). It only enters the request loop if initialization succeeds.

If initialization fails, the worker prints ehci_core: EHCI initialization failed followed by ehci_core exits... and stops the thread. The device stays registered, so open requests can still be queued for it even though nothing will ever reply to them.

Controller initialization

The capability registers start at physical address 0x0D040000 and the operational registers at 0x0D040010.

init_ehci requires USBSTS.HCHalted to be set before it requests a controller reset and fails immediately if the bit is clear. It then sets USBCMD.HCRESET, waits two microseconds and checks whether the reset has completed. While the bit stays set it polls up to 100 more times, waiting one microsecond before each read.

Once the reset completes, the driver requires these exact register values and fails initialization on any mismatch:

Schedule control

enable_async_schedule (0x138C49B8) and enable_periodic_schedule (0x138C4A24) both go through set_schedule (0x138C48FC). Before changing an enable bit, this helper waits for the matching status bit to agree with the enable bit's current value. It returns -10 if that wait times out. Both wrappers retry until the helper succeeds.

Port scan

scan_ports (0x138C3448) reads each port's status from 0x0D040050 + 4 * port, with ports numbered from 1. It only runs port change handling for a port when one of these bits is set:

The scan disables the port change interrupt while it examines the ports. Before returning it acknowledges the pending port change status and enables the interrupt again.