Why temporal buffer size BUF_SZ is directly coupled to BOOT_MAX_ALIGN?

[tito97sp]

On the latest versions the constant BUF_SZ, that is used to set the length of the temporal buffer for the regions copy, has been directly coupled to the BOOT_MAX_ALIGN constant.

https://github.com/mcu-tools/mcuboot/blob/main/boot/bootutil/src/loader.c#L71-L88
https://github.com/mcu-tools/mcuboot/blob/main/boot/bootutil/src/loader.c#L955

One of the issues that have arise with this new changes is the impossibility of setting the temporal buffer to a bigger size independently of the size of BOOT_MAX_ALIGN. For example to reduce the number of READ-WRITE cycles when swapping large images.

As far as I know, the BOOT_MAX_ALIGN depends on the memory characteristics and the BUF_SZ just from the availability of RAM memory to allocate a bigger or smaller buffer.

What is your opinion about these topic? I would propose to:

1. not couple these two constants.
2. As a feature -> Create a configuration variable to allow the user to set at compile time the size of the temporal buffer depending on the project necessities.