Compile uClinux (6): VFS: Unable to mount root FS on unknown-block () in vdsp)

In the past two days, an ext2 image file has been created in Linux to insert it to uClinux. Code . I thought the problem with the file system should be easily solved. Who knows there was no progress during the busy three or four nights:
Linux version 2.6.19.3-ADI-2007R1.1-svn (wmz@gtw.com) (vdsp 4.5) #2 Tue Sep 25 11:24:43 CST 2007
Warning: Limiting memory to 53 MB due to hardware anomaly 05000263
Blackfin support (c) 2004-2007 Analog Devices, Inc.
Compiled for ADSP-BF561 rev 0.3
Blackfin Linux support by http://blackfin.uclinux.org/
Processor speed: 600 MHz core clock and 100 MHz system clock
Board Memory: 64 MB
Kernel managed memory: 64 MB
Memory Map:
TEXT = 0x000-0x001136a3
Init = 0x001136a3-0x00174a16
Data = 0x0017c110-0x00180cbc
Stack = 0x0017e000-0x00180000
BSS = 0x00180cbc-0x00180cbc
Available = 0x00180cbc-0x03500000
Rootfs = 0x03500000-0x03f00000
DMA zone = 0x03f00000-0x04000000
Instruction Cache Enabled
Data Cache Enabled
Hardware trace enabled
Built 1 zonelists. Total pages: 13462
Kernel command line: Root = mtdblock0 RW console = ttybf0, 57600
Refreshing ing Blackfin priority driven interrupts
PID hash table entries: 256 (Order: 8, 1024 bytes)
Dentry cache hash table entries: 8192 (Order: 3, 32768 bytes)
Inode-Cache hash table entries: 4096 (Order: 2, 16384 bytes)
Physical pages: 3500
Memory available: 52156 K/64015 k ram, (388 K init code, 1037 K kernel code, 0 K data, 1024 k dma)
Blackfin scratchpad data SRAM: 4 kb
Blackfin data_a SRAM: 16 KB
Blackfin data_ B SRAM: 16 KB
Blackfin instruction SRAM: 16 KB
Mount-Cache hash table entries: 512
Blackfin DMA Controller
Serial: Blackfin serial driver
Ramdisk driver initialized: 16 RAM disks of 4096 K size 1024 blocksize
Io scheduler anticipatory registered (default)
Io scheduler CFQ registered
Io scheduler Noop registered
UClinux [MTD]: Ram probe address = 0x3500000 size = 0xa00000
Creating 1 MTD partitions on "Ram ":
0x00000000-0x00a00000: "romfs"
UClinux [MTD]: Set romfs: ext2 to be root filesystem
Jffs2 Version 2.2. (NAND) (c) 2001-2006 Red Hat, Inc.
Jffs2: Default compression mode: Priority
VFS: cannot open root device "mtdblock0" or unknown-block (31,0)
Please append a correct "root =" Boot Option
Kernel panic-not syncing: VFS: Unable to mount root FS on unknown-block (31,0)
From the prompt, we can see that ramdisk has been successfully created and the required modules have been loaded. During tracking, we found that functions such as mtd_open will not be called, in addition, only the register function is called for MTD-related functions.

It seems that you have to study file management first!