嵌入式linux2.6.19 arm9200

我是基于linux2.6.19在arm9200上开发的程序。现在主要是对好多u盘都不能mount上去。插上u盘提示usb 1-1: new full speed USB device using at91_ohci and address 13
usb 1-1: Product: Miniking Device
usb 1-1: Manufacturer: aigo
usb 1-1: SerialNumber: LBM9Q2O8
usb 1-1: configuration #1 chosen from 1 choice
scsi6 : SCSI emulation for USB Mass Storage devices
scsi 6:0:0:0: Direct-Access aigo Miniking 8.01 PQ: 0 ANSI: 2
SCSI device sda: 7878654 512-byte hdwr sectors (4034 MB)
sda: Write Protect is off
sda: assuming drive cache: write through
SCSI device sda: 7878654 512-byte hdwr sectors (4034 MB)
sda: Write Protect is off
sda: assuming drive cache: write through
sda:<7>usb-storage: queuecommand called
sda1
sd 6:0:0:0: Attached scsi removable disk sda


再调用mount( dev_path, mount_point, "vfat", 0, 0 )
（第一个参数为我的u盘目录 第二个为挂接点）
提示为
#FAT: invalid media value (0x00)
VFS: Can't find a valid FAT filesystem on dev sda.
FAT: invalid media value (0x00)
VFS: Can't find a valid FAT filesystem on dev sda.


这是为什么？求各位大侠指导
问题补充：我的LINUX2.6.19内文件系统配置
* VFAT(Windows-95) fs support
437 Default codepage for FAT
ISO8859-1 Default iocharset for FAT


我插上另外的用uformat格式化 这里选参数为0参数，就能使用
插上该盘后打印
usb 1-1: new full speed USB device using at91_ohci and address10
usb 1-1: Product:
USB2.0 FlashDisk
usb 1-1: Manufacturer: KINGMAX
usb 1-1: SerialNumber: 0807131950492
scsi4 : SCSI emulation for USB Mass Storage devices
scsi 4:0:0:0: Direct-Access KINGMAX USB2.0 FlashDisk 1.00 PQ: 0 ANSI: 2
SCSI device sdb: 1966080 512-byte hdwr sectors (1007 MB)
sdb: Write Protect is off
sdb: assuming drive cache: write through
SCSI device sdb: 1966080 512-byte hdwr sectors (1007 MB)
sdb: Write Protect is off
sdb: assuming drive cache: write through
sdb:<7>usb-storage: queuecommand called
unknown partition table
sd 4:0:0:0: Attached scsi removable disk sdb
我调用函数nRet = mount( dev_path, mount_point, "vfat", 0, 0 );返回值为0
这下就能发现读取u盘内容.
若不用低格工具返回的为-1
不能挂载u盘
问题补充：谢谢您的回答，这么说我的格式化后的u盘，系统都当做软盘来挂接了，因为格式成了系统不识别的分区了。
识别分区是不是就是识别文件系统，而我的系统不支持识别的文件系统所以挂接不了？？？？？
不识别分区可以当软盘挂接，这到底是我的系统不支持fat文件系统，还是usb驱动问题。请大侠给与指导