micropython.cmake

# cameraif: MIPI-CSI camera capture as a MicroPython native module.
#
# MicroPython's Makefile-based ports get nothing from micropython.mk: every
# line of this module is ESP32-P4 CSI hardware, so there is nothing a unix
# build could compile. micropython.mk is CircuitPython's route in, since
# CircuitPython builds its espressif port with make. On a CMake port without
# CSI the Python-facing functions still exist -- mod_cameraif.c guards its
# bodies -- so an application can ask `cameraif.available()` rather than
# catching ImportError.
set(CAMERAIF_MOD_DIR ${CMAKE_CURRENT_LIST_DIR})
set(CAMERAIF_SRC_DIR ${CAMERAIF_MOD_DIR}/src)

add_library(usermod_cameraif INTERFACE)

target_sources(usermod_cameraif INTERFACE
    ${CAMERAIF_SRC_DIR}/mod_cameraif.c
    ${CAMERAIF_SRC_DIR}/sensor_table.c
)

target_include_directories(usermod_cameraif INTERFACE
    ${CAMERAIF_SRC_DIR}
)

# The IDF components this module drives. Declared rather than assumed: a
# usermod is an INTERFACE library added to `main`, so it only sees what main
# already required -- esp_driver_cam and esp_driver_jpeg are not in that set,
# and without these the headers are simply not on the include path.
#
# Only on ESP-IDF, though. The header comment above promises this module builds
# on rp2 and unix with mod_cameraif.c's bodies guarded, but linking idf::
# targets unconditionally broke that promise: on an rp2 build CMake fails
# outright because those targets do not exist, taking the whole firmware with
# it. Found building for a Pico.
if(ESP_PLATFORM)
    target_link_libraries(usermod_cameraif INTERFACE
        idf::esp_driver_cam
        idf::esp_driver_isp
        idf::esp_driver_jpeg
    )
endif()

# Note there is deliberately no `-u ov5647_detect` here.
#
# Sensor drivers register their probe in a linker section that nothing in C
# ever names, so --gc-sections would drop them -- but esp_cam_sensor's own
# CMakeLists already emits the `-u` when CONFIG_CAMERA_OV5647_AUTO_DETECT_
# MIPI_INTERFACE_SENSOR is set. Adding it here as well looked harmless and
# was not: with CONFIG_CAMERA_OV5647 unset the driver is not compiled at all,
# so the forced reference resolved to nothing, the link still succeeded, and
# the detect array was empty with `ov5647_detect` left undefined in the ELF.
# The camera then reports "no sensor answered on SCCB" -- a wiring-shaped
# error for a build-configuration cause. The sdkconfig options are what
# matter; they live in the cameraif patch.

target_link_libraries(usermod INTERFACE usermod_cameraif)

# --- which cameraif this firmware was built from ----------------------
# Computed at build time from this repo's own git, never stored; "unknown" when
# there is no git (a tarball). Read on a target as <module>.__revision__.
execute_process(
    COMMAND git -C ${CAMERAIF_MOD_DIR} describe --always --dirty --abbrev=7
    OUTPUT_VARIABLE CAMERAIF_REVISION
    OUTPUT_STRIP_TRAILING_WHITESPACE
    ERROR_QUIET)
if(NOT CAMERAIF_REVISION)
    set(CAMERAIF_REVISION "unknown")
endif()
target_compile_definitions(usermod_cameraif INTERFACE CAMERAIF_REVISION=\"${CAMERAIF_REVISION}\")