6 lines
2.1 KiB
Markdown
6 lines
2.1 KiB
Markdown
# libSceUsbd technical debt
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### Silent stubs
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- [libSceUsbd](../../../core/libs/prx/libSceUsbd/Export.cpp) implements only the no-device path: `sceUsbdInit` and `sceUsbdExit` succeed without a host USB context, the device list is always empty and event handling waits for its timeout; calls that need a device throw. Transfers follow the `libusb_transfer` layout from [libusb.h](https://github.com/libusb/libusb/blob/master/libusb/libusb.h), which [shadPS4](https://github.com/shadps4-emu/shadPS4/blob/main/src/core/libraries/usbd/usbd.h) passes to titles as `SceUsbdTransfer`: `sceUsbdAllocTransfer` zero-allocates one with its iso packet count (a negative count returns null), `sceUsbdFillInterruptTransfer` fills the fields `libusb_fill_interrupt_transfer` sets, and `sceUsbdCancelTransfer` reports `LIBUSB_ERROR_NOT_FOUND` mapped to `0x80240005` by shadPS4's `0x80240000 - error` rule, since no transfer can be submitted. `sceUsbdEventHandlingOk` returns 1 because no other thread handles events, and `sceUsbdFreeConfigDescriptor` accepts only null because no descriptor is ever returned. The device and handle calls take the argument lists of FreeBSD 11.4 libusb ([libusb.h](https://github.com/freebsd/freebsd-src/blob/d106002967eff712894ab8b5337bbbff106ce5e0/lib/libusb/libusb.h)) and return `0x80240002` for the null arguments it rejects with `LIBUSB_ERROR_INVALID_PARAM` ([libusb10.c](https://github.com/freebsd/freebsd-src/blob/d106002967eff712894ab8b5337bbbff106ce5e0/lib/libusb/libusb10.c), [libusb10_desc.c](https://github.com/freebsd/freebsd-src/blob/d106002967eff712894ab8b5337bbbff106ce5e0/lib/libusb/libusb10_desc.c), [libusb10_io.c](https://github.com/freebsd/freebsd-src/blob/d106002967eff712894ab8b5337bbbff106ce5e0/lib/libusb/libusb10_io.c)); a null device or handle in the calls it treats as null-safe returns 0, null or nothing, as there. `sceUsbdOpen` and `sceUsbdGetActiveConfigDescriptor` throw on a null device, which libusb dereferences. Any other device or handle was never returned by this library, so those calls throw. The layout, the argument lists and the error codes are unverified on PS5
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