Cannot mount ubifs partition

[Michael N]

I am using a Zynq7000 with NAND 512MB and I am trying to deploy Linux on NAND
memory. I use a custom built kernel with minimal features (UBI and UBIFS
support are enabled and mtd-utils installed). I can ubiformat an mtd
partition, I
can ubiattach and ubidetach it but whenever I try to mount the
partition I get this error.

           mount: mounting /dev/ubi0:ubi-rootfs on /mnt/ubifs failed:
No such device

(ubi-rootfs is the name of the partition, I am sure about it)

I am sorry if I am asking about a problem that has been reported before,
but I am
new to this list

Thanks in advance,
Michael