access pci from user space

[Wim Vanderbauwhede]

Hi,

Your mail was not lost.

I'm not an expert, but I was wondering if this could help you:
On embedded systems, you would access the memory mapped IO without
using /dev/mem, but by directly accessing the memory locations. I don't
think you need mmap, as you can allocate memory in your code in the
usual fashion (statically or with malloc).

Following snippet are some convenience functions:
<snip
src="http://www.koders.com/c/fidF8BACE7ED1FDC791C586365DF3A7700993B294A7.aspx">
/*
 * readX/writeX() are used to access memory mapped devices. On some
 * architectures the memory mapped IO stuff needs to be accessed
 * differently. On the x86 architecture, we just read/write the
 * memory location directly.
 */
#define readb(addr) (*(volatile unsigned char *) (addr))
#define readw(addr) (*(volatile unsigned short *) (addr))
#define readl(addr) (*(volatile unsigned int *) (addr))

#define writeb(b,addr) ((*(volatile unsigned char *) (addr)) = (b))
#define writew(b,addr) ((*(volatile unsigned short *) (addr)) = (b))
#define writel(b,addr) ((*(volatile unsigned int *) (addr)) = (b))

#define memset_io(a,b,c)	memset((void *)(a),(b),(c))
#define memcpy_fromio(a,b,c)	memcpy((a),(void *)(b),(c))
#define memcpy_toio(a,b,c)	memcpy((void *)(a),(b),(c))
</snip>

The "volatile" keyword is important, as it tells the compiler not to try anything fancy for that memory location, no optmisations etc.

If you have an OS with a filesystem, you can try to use the /dev block devices.

You can find the actual memory values for pci from /proc/pci (cat /proc/pci)

HTH,

Wim

On Sun, 2005-02-27 at 19:41 +0100, Dominik Meyer wrote:
> Hello,
> 
> i'm currently trying to do something like pciproxy
> (http://scaramanga.co.uk/stuff/qemu-pciproxy/) for mol to let the
> Airport driver from OsX access the real hardware.
> 
> Now i've come to the point where i have to access the pci device.
> I thought it should be possible, to do that from user space and i wrote
> a little application to test this, but it didn't work:
> 
> base = 0xa0006000; // the address from /proc/bus/pci/devices like
>                    // described on
>                    // http://www.linuxjournal.com/article/5442
> length = 0x2000;
> 
> fd = open("/dev/mem", O_RDWR|O_SYNC);
> 
> map = mmap(NULL, length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, base);
> if (map == MAP_FAILED) {
>         printf("map failed\n");
>         exit(1);
> }
>  
> memcpy(&buf, map, 0x10);
> 
> and then it crashes with a "Bus Error". I have no idea why?
> Anybody can help me out?
> 
> Dominik
> 
> (Full source: http://mitglied.lycos.de/phpspacer/blog/pcitest.c)
> 
> _______________________________________________
> mol-general mailing list
> mol-general at lists.maconlinux.org
> http://lists.maconlinux.org/mailman/listinfo/mol-general
-- 
Wim Vanderbauwhede <wim at motherearth.org>
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