* Memory Access Problem
@ 2001-05-15 6:36 Rich.Liu
2001-05-15 9:40 ` Alan Cox
0 siblings, 1 reply; 2+ messages in thread
From: Rich.Liu @ 2001-05-15 6:36 UTC (permalink / raw)
To: linux-kernel
I have a problem in kernel 2.4.4
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 ?
--
Richliu
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Memory Access Problem
2001-05-15 6:36 Memory Access Problem Rich.Liu
@ 2001-05-15 9:40 ` Alan Cox
0 siblings, 0 replies; 2+ messages in thread
From: Alan Cox @ 2001-05-15 9:40 UTC (permalink / raw)
To: Rich.Liu; +Cc: linux-kernel
> 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
not.
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
phys_to_virt()
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.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2001-05-15 9:40 ` Alan Cox
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