LINUX2.6内核中用户空间向驱动程序传递的内存大小最大为多少？

 LINUX2.6内核中用户空间向驱动程序传递的内存大小最大为多少？似乎是一个页的大小，怎么突破这一页大小呢？

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Unable to handle kernel paging request at virtual address c48b3000
pgd = c3e90000
[c48b3000] *pgd=23c18011, *pte=00000000, *ppte=00000000
Internal error: Oops: 807 [#2] PREEMPT
Modules linked in: dram_driver [last unloaded: dram_driver]
CPU: 0    Tainted: G      D    (2.6.26.6 #9)
PC is at dram_write+0x60/0x1a0 [dram_driver]
LR is at vprintk+0x370/0x3d8
pc : [<bf000098>]    lr : [<c003a7f0>]    psr: 80000013
sp : c3e1ff30  ip : 00014fe7  fp : c3e1ff4c
r10: 00000000  r9 : c3e1e000  r8 : c0021ca8
r7 : 00000271  r6 : 00000201  r5 : 00014fe6  r4 : c48b3000
r3 : 00000222  r2 : 00000002  r1 : 00000200  r0 : bf0003a8
Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: c000717f  Table: 23e90000  DAC: 00000015
Process dram_test (pid: 870, stack limit = 0xc3e1e268)
Stack: (0xc3e1ff30 to 0xc3e20000)
ff20:                                     c3e05700 00011fe6 c3e1ff78 00001d4c
ff40: c3e1ff74 c3e1ff50 c0086fc0 bf000048 00000001 00000001 00000000 00000000
ff60: c3e05700 00000004 c3e1ffa4 c3e1ff78 c00875e0 c0086f14 00000000 00000000
ff80: c3e1ffac 00000000 c0021058 00000000 00000000 0000844c 00000000 c3e1ffa8
ffa0: c0021b00 c00875a4 00000000 00000000 00000003 00011fe6 00001d4c 00001d4c
ffc0: 00000000 00000000 0000844c 00000004 00000000 00000000 40024000 bea84d44
ffe0: 00000000 bea84d28 00008800 400d60ac 60000010 00000003 cc33cc33 cc33cc33
Backtrace:
[<bf000038>] (dram_write+0x0/0x1a0 [dram_driver]) from [<c0086fc0>] (vfs_write+0
xbc/0x14c)
 r7:00001d4c r6:c3e1ff78 r5:00011fe6 r4:c3e05700
[<c0086f04>] (vfs_write+0x0/0x14c) from [<c00875e0>] (sys_write+0x4c/0x7c)
 r7:00000004 r6:c3e05700 r5:00000000 r4:00000000
[<c0087594>] (sys_write+0x0/0x7c) from [<c0021b00>] (ret_fast_syscall+0x0/0x2c)
 r6:0000844c r5:00000000 r4:00000000
Code: e89da8f0 e4dc3001 e5d52001 e1833402 (e1c430b0)
---[ end trace dddf31d6bbf6387b ]---
Segmentation fault

 

12日解决了此问题，原因是双口RAM按16位组织，而LINUX内核中按字节操作，所以进行ioremap()时必须按字节来算不能按字来算。同时调用了writew()之后指针应该加2.之前的原因就在于writew()中的指针超过了ioremap()定义的长度。