query on CONFIG_EXTRA_ENV_SETTINGS and boot different images

[SIMON BABY]

Hello ,
I am new to this email group.

my requirement is below:

1) I will have two linux kernel images, imageA and imageB

2) image A and image B can be on the same medium (different partition) or
different medium.

3) If there is any issue with imageA it should boot from imageB and vice
versa.

4) I would like to know what changes are required in u-boot and kernel for
achieving this.


Regards

Simon