我用的是qq2440v3的板，内核也是预装的
插入SD卡后出现一下信息，sd卡不能像u盘那样正常挂载。
是什么原因呢？请帮忙解答一下。 谢谢！



MMC: sd_app_op_cond timed out. Probably no SD-Card here.
MMC: sd_app_op_cond: at least one card is busy - trying again.
mmcblk0: mmc0:b368 SD    993792KiB
/dev/mmc/blk0:<7>MMC: starting cmd 37 arg b3680000 flags 00000009
unknown partition table
MMC: sd_app_op_cond: at least one card is busy - trying again.

现在提供的内核中没有加载SD驱动

那就是说SD卡在当前的内核是不能用的是吧？

mmcblk0: mmc0:b368 SD    993792KiB

奇怪了，没有加载SD卡驱动，这个信息是怎么出来的？

对呀，没有加载驱动班子怎么会识别SD卡的？
而且用你们的测试程序是可以正确检测得到SD卡的。

不过你们有说明是不带MMC的，我是初学，所以还不怎么懂这句话的意思。
还有就是在 QQ2440V3  用户手册里面有关于挂接 SD 卡的说明。
“2.4.4 使用SD 卡” 在57页。

mmcblk0: mmc0:b368 SD    993792KiB
/dev/mmc/blk0:<7>MMC: starting cmd 37 arg b3680000 flags 00000009
unknown partition table

好了不浪费时间了，有这几句话至少可以说明

1. SD卡已经被检测到，并且数据可以从卡上读出
2. 这块SD卡的MBR里没有包含一个可识别的分区表

换句话说，正常情况下，这块卡会被作为一整块block设备而非单个的分区出现在系统中，类似于
/dev/mmc/blk0/disc这样的节点出现在文件系统中

所以，如果你用的是光盘上提供的内核镜像，假设设备节点是/dev/mmc/blk0/block，那只要把手册上2.4.4节的步骤稍许修改一下应该就行了
把

复制代码 mount /dev/mmc/blk0/part1 /mnt/

改成

复制代码 mount /dev/mmc/blk0/disc /mnt/

我用重新制作的内核，可以用SD卡了，哈哈，高兴，多谢斑竹的帮忙啊！
不过我还有个问题就是我拔掉SD卡后再插入就又不行了，连重新挂载都不行，必须要重新启动才可以。
那我想问下，是不是要下取消挂载再拔卡？要如何取消呢？我有用过umount，可是没效果。

拔掉SD卡后再插入就又不行了，连重新挂载都不行

你得把出错信息贴出来

[root@FriendlyARM /mnt]# umount
[root@FriendlyARM /mnt]# ls
c.mpg  c.rmv

这是我取消挂载，但是不成功。


MMC: sd_app_op_cond timed out. Probably no SD-Card here.

拔卡后出现的信息；

ls
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3912)
FAT: Directory bread(block 3912) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3913)
FAT: Directory bread(block 3913) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3914)
FAT: Directory bread(block 3914) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3915)
FAT: Directory bread(block 3915) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3916)
FAT: Directory bread(block 3916) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3917)
FAT: Directory bread(block 3917) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3918)
FAT: Directory bread(block 3918) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3919)
FAT: Directory bread(block 3919) failed
再次在 /mnt/ 目录下执行 ls 命令出现的消息；

mmcblk0: mmc0:b368 SD    993792KiB
MMC: sd_app_op_cond: at least one card is busy - trying again.
重新插上 输出的信息；

ls
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3912)
FAT: Directory bread(block 3912) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3913)
FAT: Directory bread(block 3913) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3914)
FAT: Directory bread(block 3914) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3915)
FAT: Directory bread(block 3915) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3916)
FAT: Directory bread(block 3916) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3917)
FAT: Directory bread(block 3917) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3918)
FAT: Directory bread(block 3918) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3919)
FAT: Directory bread(block 3919) failed
再次执行 ls 命令出现的消息；

mount /dev/mmc/blk0/disc /mnt/
mount: Mounting /dev/mmc/blk0/disc on /mnt/ failed: Device or resource busy
再次挂载 sd 卡后出现的消息；

ls
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3912)
FAT: Directory bread(block 3912) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3913)
FAT: Directory bread(block 3913) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3914)
FAT: Directory bread(block 3914) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3915)
FAT: Directory bread(block 3915) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3916)
FAT: Directory bread(block 3916) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3917)
FAT: Directory bread(block 3917) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3918)
FAT: Directory bread(block 3918) failed
generic_make_request: Trying to access nonexistent block-device mmcblk0 (3919)
FAT: Directory bread(block 3919) failed
最后在 /mnt/ 目录下执行 ls 命令出来的消息。

帮忙看看是怎么回事呢？谢谢！

如果你把SD卡mount在/mnt目录的话，umount的时候最好不要在/mnt目录下执行，因为umount命令会修改/mnt目录的内容，你可以试试

复制代码 cd / && umount /mnt