Fishwaldo opened a new pull request, #19751:
URL: https://github.com/apache/nuttx/pull/19751
## Summary
This is mainly a quality of life improvement for anyone debugging USB on
NuttX.
When a device is plugged in, the host says nothing about it. If a class
driver claims it, a node appears in `/dev` and you can infer what happened. If
nothing claims it, an unsupported device or a supported one whose driver is not
in the build, there is no output at all, and no way to tell the difference
between "unsupported device" and "nothing plugged in". The information exists;
it is simply thrown away unless you enable `CONFIG_DEBUG_USB_INFO`, which then
buries it in everything else the stack has to say.
`CONFIG_USBHOST_ANNOUNCE` reports each device once as it is enumerated, in a
shape people will recognise from other systems: where it is, what it is, its
vendor, product and release, and the maker, product and serial number the
device reports in its own string descriptors.
```
usb 0-5.2: new device, idVendor=46f4, idProduct=0001, bcdDevice=0.00
usb 0-5.2: mass storage, driver attached
usb 0-5.2: Product: QEMU USB HARDDRIVE
usb 0-5.2: Manufacturer: QEMU
usb 0-5.2: SerialNumber: 1-0000:00:04.0-1.2
```
Three details are deliberate. The port is given as the path from the root
hub and named by bus, because a device on a hub's first port and one on a
controller's first port are otherwise reported identically. The report is made
after binding rather than from within it, because a composite device never
reaches the ordinary class lookup, `usbhost_composite()` binds it first, and
reporting from there leaves precisely the multi-function devices unmentioned.
And whether a driver claimed the device is tracked explicitly rather than read
from the returned status, which the per-interface loop sets to `OK` regardless.
## Impact
- **User visible:** one line per device plus its strings, when the option is
on. Nothing else changes.
- **Default `n`**, so no existing configuration is affected.
- **Cost when enabled:** three extra control transfers per device, for the
three strings, taken once at enumeration and only because a report was asked
for.
- **All host controllers:** this is in `usbhost_enumerate()`, the common
path all 27 in-tree HCDs use.
- **New field:** `struct usbhost_roothubport_s` gains a `bus` number so a
port can be named on a system with more than one controller. A driver that does
not set it reports zero, which is the only bus it has.
- **Compatibility, hardware, documentation, security:** unaffected.
## Testing
**Host:** macOS 15.5 (Apple Silicon). **qemu:** 10.1.5 with KVM on Fedora 43
x86_64.
Four devices behind a hub on `qemu-xhci`: mass storage, a keyboard, and a
USB audio device that NuttX has no driver for. Same tree and topology in both
runs, differing only in `CONFIG_USBHOST_ANNOUNCE`.
**Without the option**, the entire bus, in full:
```
/dev:
kbda
sda
```
Two nodes appeared. Nothing says the hub exists, and nothing says the audio
device was ever attached.
**With the option:**
```
usb 0-5: hub, driver attached Product: QEMU USB Hub
usb 0-5.2: mass storage, driver attached Product: QEMU USB HARDDRIVE
usb 0-5.3: keyboard, driver attached Product: QEMU USB Keyboard
usb 0-5.4: audio, no driver Product: QEMU USB Audio
```
The unclaimed audio device is the point: it produces no `/dev` node either
way, so without this there is nothing at all to tell you it is present, what it
is, or why nothing happened.
These runs were made with #19745 applied underneath, because
`qemu-intel64:jumbo` is the only in-tree configuration with a USB host
controller and on current master that controller does not initialise. The
change itself is in the common enumeration path and is independent of any host
controller.
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