Hi Vishal,
For the SD MMC test on Samsung Arndale board, the value of EXTERNAL_STORAGE doesn't match with the output of "df":
root@arndale:/ # df
Filesystem Size Used Free Blksize
/dev 1000.6M 164.0K 1000.4M 4096
/mnt/asec 1000.6M 0.0K 1000.6M 4096
/mnt/obb 1000.6M 0.0K 1000.6M 4096
/system 739.9M 371.1M 368.8M 4096
/cache 243.9M 2.0M 241.9M 1024
/data 487.8M 51.4M 436.4M 1024
/mnt/media_rw/sdcard0 5.8G 12.0K 5.8G 4096
/mnt/secure/asec 5.8G 12.0K 5.8G 4096
root@arndale:/ # echo $EXTERNAL_STORAGE
/storage/sdcard0
root@arndale:/ #
"/storage/sdcard0" is not in the output of "df". According to the output, the storage actually locates at "/mnt/media_rw/sdcard0", and I couldn't see there is any symbol link between them:
root@arndale:/ # busybox ls -ld /mnt/media_rw/sdcard0
drwxrwx--- 4 media_rw media_rw 4096 Jan 1 00:01 /mnt/media_rw/sdcard0
root@arndale:/ # busybox ls -ld /storage/sdcard0
drwx------ 2 root root 0 Jan 1 00:00 /storage/sdcard0
root@arndale:/ #