usbus: allow to forward EP0 transfer events to other handlers

[dylad]

Contribution description

This PR introduces a new usbus handler flag to allows to forward transfer complete event from EP0 only (control endpoints) to other handlers.
The idea is to let other interfaces know the state of the transfer on these EPs. Each interface should could set this flag (at any moment) so it will receive these events.

For a more real use case on DFU:
Currently, DFU uses ztimer for a unique purpose, schedule the reboot. At the end of the firmware transfer, dfu-util will request the 'DFU state' of the device. Device must answer it, then reboot to start the newly flashed application. Thus, we cannot simply reboot as soon as we fill the buffer and ready the transfer with usbdev_ep_xmit(). We need to wait the end of the transfer and that the host ACK it. This is why ztimer was used. To wait a bit, to let the transfer completes properly, then reboot. Rebooting without this small delay, leads to an error in dfu-util message log (but the device is correctly flashed).
dfu-util: unable to read DFU status after completion (LIBUSB_ERROR_PIPE)

Nevertheless, using ztimer for this purpose is more a workaround than a proper solution. That's why, a new flag is introduced by this PR. Each handler can set this bit at any point in time (we don't necessarily need it all the time). When the EP0 transfer event handling is done by usbus, it will loop through all available handlers (except the first one which is already being call, to avoid a deathloop) and forward the event to interfaces that need it.

ztimer is now optional for riotboot_dfu. It will only init ztimer if the dependency is pull by another module (e.g periph_usbdev on STM32).

If ztimer dependency was only pull by DFU, this PR allows to reduce the bootloader size:

saml21-xpro master arm-none-eabi-gcc (Arm GNU Toolchain 12.2.MPACBTI-Bet1)
   text    data     bss     dec     hex filename
  11464      20    2936   14420    3854 /home/dylan/work/RIOT/bootloaders/riotboot_dfu/bin/saml21-xpro/riotboot_dfu.elf
make : on quitte le répertoire « /home/dylan/work/RIOT/bootloaders/riotboot_dfu »

saml21-xpro w/ PR same toolchain

   text    data     bss     dec     hex filename
   9776       0    2816   12592    3130 /home/dylan/work/RIOT/bootloaders/riotboot_dfu/bin/saml21-xpro/riotboot_dfu.elf
make : on quitte le répertoire « /home/dylan/work/RIOT/bootloaders/riotboot_dfu »

Testing procedure

Flash riotboot_dfu on any board that support periph_usbdev and riotboot
make -j8 BOARD=xxxx -C bootloaders/riotboot_dfu flash

Reboot into bootloader by resetting your board while pushing on BTN0.

Then flash any test app on your board through DFU:
PROGRAMMER=dfu-util USEMODULE=usbus_dfu make -j8 BOARD=xxxx -C tests/shell riotboot/flash-slot1

Board should reboot automatically and start the newly flashed test application.
No error message are reported by dfu-util

Issues/PRs references

None.

[benpicco]

Suggested change

	if(usbus_handler_isset_flag(hdl, USBUS_HANDLER_FLAG_TR_EP0_FWD)) {
	if (usbus_handler_isset_flag(hdl, USBUS_HANDLER_FLAG_TR_EP0_FWD)) {

[benpicco]

So EP0 means transfer complete?

[riot-ci]

Murdock results

✔️ PASSED

4b57db1 bootloaders/riotboot_dfu: optionally init ztimer

Success	Failures	Total	Runtime
6931	0	6931	10m:41s

Artifacts

• Documentation preview