ricardgb commented on PR #19371:
URL: https://github.com/apache/nuttx/pull/19371#issuecomment-4917465310
Sure — here are before/after logs.
**Setup:** `raspberrypi-pico` (RP2040), Linux host. Built standalone
`CONFIG_NET_CDCECM` (and separately `CONFIG_NET_CDCNCM`). The rp2040 board
doesn't instantiate these classes by default, so I added a
`cdcecm_initialize()` / `cdcncm_initialize()` call in the board bringup purely
to exercise the driver (test scaffolding, not part of this PR). Relevant
detail: `rp2040_usbintr_busreset()` drops the D+ pull-up on every bus reset,
which is exactly what makes the missing re-connect fatal on this controller.
### CDC-ECM — without the fix (baseline)
After the board is flashed and reboots into NuttX, the device never
enumerates:
```
usb 3-1: USB disconnect, device number 55 # bootloader gone; board
reboots into NuttX
# ... and nothing further:
the CDC-ECM device never appears
```
```
host: no cdc_ether interface
host: lsusb | grep -i cdc -> (no CDC device)
```
### CDC-ECM — with the fix
```
usb 3-1: New USB device found, idVendor=0525, idProduct=a4a2, bcdDevice= 1.00
usb 3-1: Product: CDC/ECM Ethernet
usb 3-1: Manufacturer: NuttX
cdc_ether 3-1:1.0 usb0: register 'cdc_ether' at usb-0000:00:14.0-1, CDC
Ethernet Device, 02:00:00:11:22:33
```
```
$ ping -c 4 192.168.7.1
64 bytes from 192.168.7.1: icmp_seq=1 ttl=64 time=0.959 ms
64 bytes from 192.168.7.1: icmp_seq=2 ttl=64 time=0.550 ms
64 bytes from 192.168.7.1: icmp_seq=3 ttl=64 time=0.585 ms
64 bytes from 192.168.7.1: icmp_seq=4 ttl=64 time=0.535 ms
--- 192.168.7.1 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3061ms
rtt min/avg/max/mdev = 0.535/0.657/0.959/0.175 ms
```
### CDC-NCM — with the fix
Same one-liner in `cdcncm_disconnect()`. The device now enumerates and the
host binds `cdc_ncm` (it previously never attached at all):
```
usb 3-1: New USB device found, idVendor=0525, idProduct=a4a2, bcdDevice= 1.00
usb 3-1: Product: CDC/NCM Ethernet
usb 3-1: Manufacturer: NuttX
cdc_ncm 3-1:1.0: MAC-Address: 02:00:00:11:22:33
cdc_ncm 3-1:1.0 usb0: register 'cdc_ncm' at usb-0000:00:14.0-1, CDC NCM (NO
ZLP), 02:00:00:11:22:33
```
The NCM interface comes up `NO-CARRIER` due to the separate, pre-existing
interrupt-IN endpoint issue on this controller that I noted in the PR
description (out of scope here). The part this fix restores — enumeration and
driver binding — works.
---
*Disclosure: these logs, and the fix and its validation, were produced by an
AI agent (Claude Code, operated and directed by me) and reviewed by me before
posting.*
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