TQ210开发板中LED驱动的疑问？？？

1.TQ210开发板中，自带的led驱动，也就是/driver/char/tq210_leds.c中的第118行，将函数s3c_gpio_setpin(gpio_table[i], 0);注释掉了，请问不能直接用这个函数吗？为什么要改成 gpio_direction_output(gpio_table[arg], cmd)？
2.为什么我在自己写的led驱动中，使用了s3c_gpio_setpin(gpio_table[i], 0)这个函数后，控制台报错呢？

报错信息：
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = f3764000
[00000000] *pgd=5377e031, *pte=00000000, *ppte=00000000
Internal error: Oops: 80000007 [#1] PREEMPT
last sysfs file: /sys/devices/virtual/MY_LEDS/MY_LEDS/dev
Modules linked in: myled rt5370sta ds18b20 s5pv210_hdmi wm8960
CPU: 0    Not tainted  (2.6.35.7-EmbedSky #2)
PC is at 0x0
LR is at s3c_gpio_setpin+0x4c/0x60
pc : [<00000000>]    lr : [<c004dde8>]    psr: a0000093
sp : f361dec0  ip : f361ded8  fp : f361ded4
r10: 00000000  r9 : f361c000  r8 : 00000000
r7 : 00000001  r6 : 00000001  r5 : 00000001  r4 : a0000013
r3 : 00000000  r2 : fffffff0  r1 : 00000004  r0 : c09eccb0
Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 10c5387d  Table: 53764019  DAC: 00000015

LR: 0xc004dd68:
dd68  e121f000 e1a0200d e3c23d7f e3c3303f e5932004 e2422001 e5832004 e5933000
dd88  e3130002 0a000000 eb1aa558 e3a00000 e89da800 e1a0c00d e92dd830 e24cb004


Backtrace:
[<c004dd9c>] (s3c_gpio_setpin+0x0/0x60) from [<bf0ad07c>] (led_ioctl+0x44/0x8c [myled])
r5:00000001 r4:00000001
[<bf0ad038>] (led_ioctl+0x0/0x8c [myled]) from [<c0100dac>] (vfs_ioctl+0x84/0xb4)
r5:00000000 r4:f3780700
[<c0100d28>] (vfs_ioctl+0x0/0xb4) from [<c0101404>] (do_vfs_ioctl+0x52c/0x57c)
r7:00000003 r6:00000001 r5:f3780700 r4:00000001
[<c0100ed8>] (do_vfs_ioctl+0x0/0x57c) from [<c01014ac>] (sys_ioctl+0x58/0x7c)
r9:f361c000 r8:00000000 r7:00000003 r6:00000001 r5:00000001
r4:f3780700
[<c0101454>] (sys_ioctl+0x0/0x7c) from [<c003bfc0>] (ret_fast_syscall+0x0/0x30)
r8:c003c168 r7:00000036 r6:00000000 r5:00000000 r4:00000000
Code: bad PC value
---[ end trace 9e6030fb6e663a2e ]---
Segmentation fault

1,。gpio_direction_output(gpio_table[arg], cmd)是方便hal层调用。
2.存在空指针错误。