mmap problem

["Usman S. Ansari" <uansari@yahoo.com>]

I am trying to mmap a device on PPC plateform. The device is at address space of 10100000
(0x9a1d20). From within the driver I can read / write to the memory. But when I try to read /
write from a user space program after memory mapping, I get SIGSEGV. PLEASE HELP.

The code for mmap:
static int ocr_mmap(struct file *file, struct vm_area_struct *vma)
{
 unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
 int minor = MINOR(file->f_dentry->d_inode->i_rdev);

 dT[minor].addr = (int) __va(dT[minor].addr);

 if (remap_page_range(vma->vm_start,                  /* start addr in process addr space */
                      dT[minor].addr + offset,        /* addr to map */
		      vma->vm_end - vma->vm_start,    /* size to map */
		      vma->vm_page_prot) < 0)         /* flags */
    return -EAGAIN;

 return(0);
}
The code for mmap in user space:

int main(void)
{
 int  fd, i;
 char *ptr, *qtr;
 
 if ((fd = open("/dev/ocr_reg", O_RDWR)) < 0)
    exit(1);

 if ((ptr = (char *) mmap(0, OCR_REG_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == NULL)
    {
     perror("error mmapping /dev/ocr_reg");
     exit(1);
    }

 printf("/dev/ocr_reg mmaped @ %x\n", ptr);

 qtr = ptr;
 printf("Testing Register Area - Reading # 1\n");
 printf("Address of ptr = %x\n", ptr);
 printf("Address of qtr = %x\n", qtr);
 printf("%x", *qtr); qtr++;
 printf("%x", *qtr); qtr++;
 printf("%x", *qtr);

 qtr = ptr;
 printf("Testing Register Area - Writing\n");
 *qtr = 0xf0; qtr++;
 *qtr = 0x0f; qtr++;
 *qtr = 0xcc;

 qtr = ptr;
 printf("Testing Register Area - Reading # 2\n");
 printf("%x", *qtr); qtr++;
 printf("%x", *qtr); qtr++;
 printf("%x", *qtr);

 if (munmap(0, OCR_REG_SIZE) != 0)
    printf("munmap of /dev/ocr_reg failed\n");
}
The include files are:
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/malloc.h>

#include <asm/mpc8xx.h>
#include <asm/8xx_immap.h>
#include <commproc.h>

Make flags:
CC = ppc_8xx-gcc

CFLAGS_K =		-D__KERNEL__ $(NO_HARDWARE_FLAG) \
			-DMODULE -DMODVERSIONS \
			-D__powerpc__ -mcpu=860 \
			-Wall -Wstrict-prototypes \
			-Wno-uninitialized \
			-fomit-frame-pointer \
			-fsigned-char -msoft-float \
			-fno-builtin -ffixed-r2 \
			-pipe -mmultiple -mstring \
			-Os \
			-I/linux-2.4.4/include \
			-I/linux-2.4.4/arch/ppc/8xx_io

=====
Usman S. Ansari
Linux OS & Device Drivers

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