Re: external PCI board direct access

[aprasad@in.ibm.com]

>I've got an external PCI board
>
>/proc/pci gives me :
>      Non-prefetchable 32 bit memory at 0xfeaff800 [0xfeaff800].
>      I/O at 0xd800 [0xd801].
>      Non-prefetchable 32 bit memory at 0xfeaa0000 [0xfeaa0000].
>      Non-prefetchable 32 bit memory at 0xfea80000 [0xfea80000].
>
>I'd like to access to memory at 0xfea80000 which is a SDRAM on my
>external board
>
>in my driver I made
>baseAddress=0xfea80000;
>sramSize=0x00020000;
>ptr = (u_int *) ioremap (baseAddress, sramSize)
>
>thanks to the pointer ptr I can access to the memory :
>        for (i = 0; i < 0x10; i++)
>                writel (i, the.ptrAccess + i);
>
>        for (i = 0; i < 0x10; i++)
>                printk ("at 0x%08x  got 0x%08x\n", i, readl
>(the.ptrAccess + i));
>
>
>---------
>
>I want to do the same thing from my application.
>I can export ptr via an ioctl () access in order to do :
>        for (i = 0; i < 0x10; i++)
>                (*(volatile u_int *) (ptr + i)) = i;
>
>        for (i = 0; i < 0x10; i++)
>                printf ("at 0x%08x  got 0x%08x\n", i, (*(volatile u_int
>*) (ptr + i)));
>
>as soon as I access to (*(volatile u_int *) (ptr + i)) I've got a
>"Segmentation fault (core dumped)"

you are passing kernel mode ptr to an user application, which will
obiviously crash on access that pointer. try to use mmap that region.
Regards,
Anil


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