dfu: mcuboot: define boot_img_magic when FLASH_AREA_IMAGE_SECONDARY

[mniestroj]

boot_img_magic[] is needed for boot_magic_write() function, which is
defined if FLASH_AREA_IMAGE_SECONDARY is defined as well.

Make sure boot_img_magic[] is defined when FLASH_AREA_IMAGE_SECONDARY.

Fixes: #30075

[de-nordic]

According to the description of the problem (#30075), the desired result is to be able to use CONFIG_IMG_MANAGER=y without support for MCUBOOT:

It is possible to use functionality provided by IMG_MANAGER without building firmware for chain-loading with mcuboot.

Shouldn't then the solution be to make a compilation of mcuboot.c optional within CMakeList.txt ?

[nvlsianpu]

We decided not to use not in zephyr tree defined Kconfig properties here.
Then fastest patch is to add || defined(CONFIG_IMG_MANAGER) or && !defined(CONFIG_IMG_MANAGER) where needed.
Also want to emphasize that I will work on #29963 soon

[mniestroj]

We decided not to use not in zephyr tree defined Kconfig properties here.

But still decided to make a logic based on "not in zephyr tree" code, its public functions etc. IMO it doesn't seem any better, because dependency is still there. The only thing is that Compliance check is satisfied, which is kind of artificial gain.

Then fastest patch is to add || defined(CONFIG_IMG_MANAGER) or || !defined(CONFIG_IMG_MANAGER) where needed.

Unfortunately defined(CONFIG_IMG_MANAGER) still doesn't tell us if we are building within mcuboot or not.

Also want to emphasize that I will work on #29963 soon

Seems like a very good idea, we really need that! Any estimates on that already?

What about adding a helper macro #define WITHIN_MCUBOOT (whatever_magic_needs_to_be_here) and then use #if WITHIN_MCUBOOT and #if !WITHIN_MCUBOOT statements all across the codebase? This will at least show what logic we are relying on, while defined(CONFIG_BOOTLOADER_MCUBOOT) doesn't tell anything for now. Personally I think that we should use CONFIG_MCUBOOT, but if that is really not desirable then at least:

#if !defined(CONFIG_BOOTLOADER_MCUBOOT) && !defined(CONFIG_IMG_MANAGER) && !defined(CONFIG_ZTEST)
#define WITHIN_MCUBOOT 1
#endif

[nvlsianpu]

WITHIN_MCUBOOT sound ok to me.

[mniestroj]

I am not sure that adding a check around CONFIG_IMG_MANAGER (when defining WITH_MCUBOOT) makes sense, because then we will run into function name conflicts with MCUboot once again, because mcuboot.c is compiled only when CONFIG_IMG_MANAGER=y. @nvlsianpu could you confirm?

[nvlsianpu]

@mniestroj ^^ obviously you are right.
looks like need to find another way - new kconfig or so

[nvlsianpu]

I started working on #29963

[nvlsianpu]

@mniestroj shall we close this?

[mniestroj]

This has been superseded with #30370.