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SubjectRe: Memory Access Problem
> I use readw to access memory below 1MB , report "Segmentation fault"
> and stall in memory
> simple code below (this will get paraller port)
> ==
> int init_module(void){
> unsigned int *BIOS_Data=(unsigned int *)0x400;
> u32 test;
> test = readw(BIOS_Data);
> printk(KERN_CRIT "0x400:%x\n",test);
> }
> ==
> but those can work in kernel 2.2.19 , no problem .
> can anyone help me ?

2.2 had back compatibility support for old drivers that did this 2.4 does

readb() is for bus accesses after mapping with ioremap
isa_readb() is a quick form for ISA bus which is always mapped

For main memory you want to use

to get the virtual mapping of the page. That will work for the BIOS page but
not for arbitary higher pages which may not even be mapped.

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