Asymmetrical OTA update partitions

[git-n-pissed]

I'm working on some OTA update code, but instead of using the standard two OTA partitions of equal size method, I would like ota_0 to be a smaller partition which contains the minimal code required to update the ota_1 partition. In this way the ota_1 partition can be much larger. Here is my partition table:

# Partition table for MicroPython with OTA support using 8MB flash
# Notes: the offset of the partition table itself is set in
# $IDF_PATH/components/partition_table/Kconfig.projbuild.
# Name,   Type, SubType, Offset,   Size,     Flags
nvs,      data, nvs,     0x9000,   0x4000,
otadata,  data, ota,     0xd000,   0x2000,
phy_init, data, phy,     0xf000,   0x1000,
ota_0,    app,  ota_0,   0x10000,  0x180000,
ota_1,    app,  ota_1,   0x190000, 0x338000,
vfs,      data, fat,     0x4c8000, 0x338000,

Currently I have two manifests; one is used as the FROZEN_MANIFEST during the ota_0 build and one is used as the FROZEN_MANIFEST during the ota_1 build. Both builds use the same partition table. The build for ota_0 works fine, but the build for ota_1 results in the following warning which is elevated to an error:

Warning: 1/2 app partitions are too small for binary micropython.bin size 0x1bf360:
  - Part 'ota_0' 0/16 @ 0x10000 size 0x180000 (overflow 0x3f360)

...

bootloader  @0x000000    18736  (   14032 remaining)
partitions  @0x008000     3072  (    1024 remaining)
application @0x010000  1831776  ( -258912 remaining)
ERROR: application overflows allocated space of 1572864 bytes by 258912 bytes
make: *** [Makefile:41: all] Error 1

This would be a heavy handed approach, but as a test I tried adding -Wno-error to the target_compile_options in ports/esp32/main/CMakeLists.txt, but to no avail:

# Disable some warnings to keep the build output clean.
target_compile_options(${MICROPY_TARGET} PUBLIC
    -Wno-clobbered
    -Wno-deprecated-declarations
    -Wno-missing-field-initializers
    -Wno-error
)

What can I do to let the build know that its target partition is ota_1 and it doesn't need to worry about the size of ota_0?

[git-n-pissed]

The "fix" was easier than I was making it. Just commented out the ota_0 partition entry when I'm building the image for ota_1.

# Partition table for MicroPython with OTA support using 8MB flash
# Notes: the offset of the partition table itself is set in
# $IDF_PATH/components/partition_table/Kconfig.projbuild.
# Name,   Type, SubType, Offset,   Size,     Flags
nvs,      data, nvs,     0x9000,   0x4000,
otadata,  data, ota,     0xd000,   0x2000,
phy_init, data, phy,     0xf000,   0x1000,
# ota_0,    app,  ota_0,   0x10000,  0x180000,
ota_1,    app,  ota_1,   0x190000, 0x338000,
vfs,      data, fat,     0x4c8000, 0x338000,

In fact, since I'm just using the micropython.bin file (as you do with OTA updates) and not the firmware.bin file, I suspect that even doing a generic build with a factory partition of the right size will work. The resulting micropython.bin image just needs to be smaller than the target OTA partition.