菜鸟请大神分析一个旋转编码器的驱动

仙凡居士

小弟最近在做一个旋转编码器的驱动程序，probe执行成功，但在执行中断处理程序时出现如下错误，请各位大神帮忙分析一下，小弟先在此谢过～～

1. 
   
2. Unable to handle kernel NULL pointer dereference at virtual address 00000008
   
3. pgd = c0004000
   
4. [00000008] *pgd=00000000
   
5. Internal error: Oops: 17 [#1] PREEMPT
   
6. Modules linked in: 8192cu
   
7. CPU: 0    Not tainted  (2.6.31 #28)
   
8. PC is at rotary_encoder_irq+0x14/0x198
   
9. LR is at rotary_encoder_irq+0x10/0x198
   
10. pc : [<c02306e0>]    lr : [<c02306dc>]    psr: 40000093
    
11. sp : c0451f28  ip : 00002cab  fp : 00000000
    
12. r10: 4001e758  r9 : c0450000  r8 : 00000001
    
13. r7 : 000000c7  r6 : c0458100  r5 : 00000000  r4 : c38d1000
    
14. r3 : c0451f50  r2 : c0451f1c  r1 : c03fcf21  r0 : 00000011
    
15. Flags: nZcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
    
16. Control: 0005317f  Table: 43be0000  DAC: 00000017
    
17. Process swapper (pid: 0, stack limit = 0xc0450270)
    
18. Stack: (0xc0451f28 to 0xc0452000)
    
19. 1f20:                   c38d1000 00000000 00000000 c0069590 c38d1000 c045e954
    
20. 1f40: 000000c7 c045b0c4 00000001 c006b300 00000000 000000c7 00000012 c0034a24
    
21. 1f60: 00000012 00000000 c001fca4 00000002 00000001 c0025068 ffffffff f0000000
    
22. 1f80: c001fca4 c0025a04 2625a000 80000013 00001000 60000013 c0450000 c001fca8
    
23. 1fa0: c001fca4 c04542f0 4001e78c 41069265 4001e758 00000000 c0458240 c0451fd0
    
24. 1fc0: c0026d58 c0030e1c 60000013 ffffffff c04887c4 c0008a5c c00085f0 00000000
    
25. 1fe0: 00000000 c001fca8 00000000 00053175 c0480a44 40008034 00000000 00000000
    
26. [<c02306e0>] (rotary_encoder_irq+0x14/0x198) from [<c0069590>] (handle_IRQ_event+0x3c/0x10c)
    
27. [<c0069590>] (handle_IRQ_event+0x3c/0x10c) from [<c006b300>] (handle_level_irq+0xc0/0x140)
    
28. [<c006b300>] (handle_level_irq+0xc0/0x140) from [<c0034a24>] (mxs_gpio_irq_handler+0x68/0x98)
    
29. [<c0034a24>] (mxs_gpio_irq_handler+0x68/0x98) from [<c0025068>] (_text+0x68/0x84)
    
30. [<c0025068>] (_text+0x68/0x84) from [<c0025a04>] (__irq_svc+0x44/0x8c)
    
31. Exception stack(0xc0451f88 to 0xc0451fd0)
    
32. 1f80:                   2625a000 80000013 00001000 60000013 c0450000 c001fca8
    
33. 1fa0: c001fca4 c04542f0 4001e78c 41069265 4001e758 00000000 c0458240 c0451fd0
    
34. 1fc0: c0026d58 c0030e1c 60000013 ffffffff
    
35. [<c0025a04>] (__irq_svc+0x44/0x8c) from [<c0030e1c>] (mx23_pm_idle+0x74/0x7c)
    
36. [<c0030e1c>] (mx23_pm_idle+0x74/0x7c) from [<c0026d58>] (cpu_idle+0x60/0xb8)
    
37. [<c0026d58>] (cpu_idle+0x60/0xb8) from [<c0008a5c>] (start_kernel+0x220/0x268)
    
38. [<c0008a5c>] (start_kernel+0x220/0x268) from [<40008034>] (0x40008034)
    
39. Code: e59f0170 e1a06001 eb0401f0 e5965004 (e5950008)
    
40. Kernel panic - not syncing: Fatal exception in interrupt
    

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中断处理程序源码如下：

1. 
   
2. static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
   
3. {
   
4.         struct rotary_encoder *encoder = dev_id;
   
5.         struct rotary_encoder_platform_data *pdata = encoder->pdata;
   
6.         int a = !!gpio_get_value(pdata->gpio_a);
   
7.         int b = !!gpio_get_value(pdata->gpio_b);
   
8.         int state;
   
9. 
   
10.         a ^= pdata->inverted_a;
    
11.         b ^= pdata->inverted_b;
    
12.         state = (a << 1) | b;
    
13. 
    
14.         switch (state) {
    
15. 
    
16.         case 0x0:
    
17.                 if (!encoder->armed)
    
18.                         break;
    
19. 
    
20.                 if (pdata->relative_axis) {
    
21.                         input_report_rel(encoder->input, pdata->axis,
    
22.                                          encoder->dir ? -1 : 1);
    
23.                 } else {
    
24.                         unsigned int pos = encoder->pos;
    
25. 
    
26.                         if (encoder->dir) {
    
27.                                 /* turning counter-clockwise */
    
28.                                 if (pdata->rollover)
    
29.                                         pos += pdata->steps;
    
30.                                 if (pos)
    
31.                                         pos--;
    
32.                         } else {
    
33.                                 /* turning clockwise */
    
34.                                 if (pdata->rollover || pos < pdata->steps)
    
35.                                         pos++;
    
36.                         }
    
37.                         if (pdata->rollover)
    
38.                                 pos %= pdata->steps;
    
39.                         encoder->pos = pos;
    
40.                         input_report_abs(encoder->input, pdata->axis,
    
41.                                          encoder->pos);
    
42.                 }
    
43.                 input_sync(encoder->input);
    
44. 
    
45.                 encoder->armed = false;
    
46.                 break;
    
47. 
    
48.         case 0x1:
    
49.         case 0x2:
    
50.                 if (encoder->armed)
    
51.                         encoder->dir = state - 1;
    
52.                 break;
    
53. 
    
54.         case 0x3:
    
55.                 encoder->armed = true;
    
56.                 break;
    
57.         }
    
58. 
    
59.         return IRQ_HANDLED;
    
60. }
    

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仙凡居士

求大神，求指导……