How to build net_lwip_webserver tinysb example in pico-examples?

[sdbbs]

The main CMakeLists.txt starts with add_subdirectory, and it does:

add_subdirectory(usb)

usb/CMakeLists.txt then does

add_subdirectory(device)

and finally, usb/device/CMakeLists.txt does:

set(FAMILY rp2040)
set(BOARD pico_sdk)
set(TINYUSB_FAMILY_PROJECT_NAME_PREFIX "tinyusb_dev_")
add_subdirectory(${PICO_TINYUSB_PATH}/examples/device tinyusb_device_examples)

add_subdirectory(dev_hid_composite)
add_subdirectory(dev_lowlevel)

For me, PICO_TINYUSB_PATH resolved to the tinyusb inside pico-sdk (e.g. /path/to/pico-sdk/lib/tinyusb), and ther e is a net_lwip_webserver subdirectory there:

$ ls /path/to/pico-sdk/lib/tinyusb/examples/device
audio_4_channel_mic/  cdc_msc_freertos/       hid_composite/           msc_dual_lun/        webusb_serial/
audio_test/           dfu/                    hid_composite_freertos/  net_lwip_webserver/  99-tinyusb.rules
board_test/           dfu_runtime/            hid_generic_inout/       uac2_headset/        CMakeLists.txt
cdc_dual_ports/       dynamic_configuration/  hid_multiple_interface/  usbtmc/
cdc_msc/              hid_boot_interface/     midi_test/               video_capture/

When I try to build pico-examples once, I can notice that a pico-examples/build/usb/device/tinyusb_device_examples directory does get created, and inside it, I can see a copy of net_lwip_webserver:

$ cd /path/to/pico-examples/build/usb/device/tinyusb_device_examples
$ ls
audio_4_channel_mic/  CMakeFiles/             hid_generic_inout/       pico-sdk/       cmake_install.cmake
audio_test/           dfu/                    hid_multiple_interface/  uac2_headset/   Makefile
board_test/           dfu_runtime/            midi_test/               usbtmc/
cdc_dual_ports/       dynamic_configuration/  msc_dual_lun/            video_capture/
cdc_msc/              hid_composite/          net_lwip_webserver/      webusb_serial/

... however, no .elf are built; if I try to issue make in this directory, a build starts and completes:

$ make
[  0%] No update step for 'ELF2UF2Build'
[  0%] No patch step for 'ELF2UF2Build'
[  0%] Performing configure step for 'ELF2UF2Build'
-- The C compiler identification is GNU 12.1.0
...
[100%] Built target tinyusb_dev_usbtmc
[100%] Built target tinyusb_dev_video_capture
[100%] Built target tinyusb_dev_webusb_serial

... however, net_lwip_webserver is still not built:

$ find . -name '*.elf'
./audio_4_channel_mic/tinyusb_dev_audio_4_channel_mic.elf
./audio_test/tinyusb_dev_audio_test.elf
./board_test/tinyusb_dev_board_test.elf
./cdc_dual_ports/tinyusb_dev_cdc_dual_ports.elf
./cdc_msc/tinyusb_dev_cdc_msc.elf
./dfu/tinyusb_dev_dfu.elf
./dfu_runtime/tinyusb_dev_dfu_runtime.elf
./dynamic_configuration/tinyusb_dev_dynamic_configuration.elf
./hid_composite/tinyusb_dev_hid_composite.elf
./hid_generic_inout/tinyusb_dev_hid_generic_inout.elf
./hid_multiple_interface/tinyusb_dev_hid_multiple_interface.elf
./midi_test/tinyusb_dev_midi_test.elf
./msc_dual_lun/tinyusb_dev_msc_dual_lun.elf
./uac2_headset/tinyusb_dev_uac2_headset.elf
./usbtmc/tinyusb_dev_usbtmc.elf
./video_capture/tinyusb_dev_video_capture.elf
./webusb_serial/tinyusb_dev_webusb_serial.elf

What would I have to do, in order to force the tinyusb net_lwip_webserver to be built as part of pico-examples?

[sdbbs]

Ok, I think I figured it out; first I noticed that the original [tinyusb/blob/master/examples/device/net_lwip_webserver/CMakeLists.txt) - unlike most other tinyusb examples - has this conditional stanza:

...
set(TOP "../../..")
get_filename_component(TOP "${TOP}" REALPATH)

if (EXISTS ${TOP}/lib/lwip/src)
    include(${TOP}/hw/bsp/family_support.cmake)
...

Basically, the project (along with the list of files to be compiled) gets created only if the ${TOP}/lib/lwip/src; in my case, these files get copied into pico-examples tree from pico-sdk; so I checked my pico-sdk path there, and while the parent lwip directory existed, the child lwip/src did not:

$ ls -la /path/to/pico-sdk/lib/tinyusb/lib/lwip/
total 4.0K
drwxr-xr-x 1 sd None 0 Mar 29 13:30 ./
drwxr-xr-x 1 sd None 0 Mar 29 13:30 ../

$ ls /path/to/pico-sdk/lib/tinyusb/lib/lwip/src
ls: cannot access '/path/to/pico-sdk/lib/tinyusb/lib/lwip/src': No such file or directory

And this "smelled" like an unitialized submodule - and indeed, it was: note that tinyusb is a submodule of pico-sdk - but it aslo turns out, lwip is a submodule of tinyusb; so apparently when I set this up, apparently I did not do recursive git submodule update:

$ cd /path/to/pico-sdk
$ git submodule status
 4bfab30c02279a0530e1a56f4a7c539f2d35a293 lib/tinyusb (0.12.0)

$ cd lib/tinyusb/
$ git submodule status
-7eb7bfa9ea4fbeacfafe1d5f77d5a0e6ed3922e7 hw/mcu/gd/nuclei-sdk
...
-159e31b689577dbf69cf0683bbaffbd71fa5ee10 lib/lwip
...

So first we need to checkout the submodules in pico-sdk:

$ cd /path/to/pico-sdk/lib/tinyusb/
$ git submodule update --init --recursive
Submodule 'hw/mcu/gd/nuclei-sdk' (https://github.com/Nuclei-Software/nuclei-sdk.git) registered for path 'hw/mcu/gd/nuclei-sdk'
...

Then, go back to pico-examples, and first repeat the cmake command in its build/ subdirectory (sometime just running make will notice changes in cmake files, and will automatically call cmake at start, but not in this case); and then finally:

$ cd /path/to/pico-examples/build/usb/device/tinyusb_device_examples
$ make
...
[100%] Linking CXX executable tinyusb_dev_net_lwip_webserver.elf
...

Nice - finally, also this example compiles!