Hi,
I trying to implement mmap method (And by the way I writing driver to
model adc). I had implemented as shown below. I am not getting the
result as I expected. But got some error: map pfn RAM range req
uncached-minus for 36a0e000-36a0f000, got write-back.
In user space, I call mmap as follows: map_ptr = (signed short *)
mmap(0,ADC_USER_MEM_SIZE,PROT_READ, MAP_SHARED,fd,0);
Am I doing anything wrong here?
static int simdrv_mmap(struct file *filp,struct vm_area_struct *vma)
{
unsigned long off = vma->vm_pgoff << PAGE_SHIFT;
unsigned long physical = (__pa((void *)adc_dev.adcMemoryArea) >>
PAGE_SHIFT) + off; // adcMemory I got via
__get_free_pages(GFP_KERNEL, 1);
unsigned long vsize = vma->vm_end - vma->vm_start;
unsigned long psize = __pa((void *) adc_dev.adcMemoryArea) - off;
// Module spanning too high
if (vsize > psize)
{
printk(KERN_ALERT "Module spanning too high");
return -EINVAL;
}
vma->vm_flags |= VM_IO;
vma->vm_flags |= VM_RESERVED;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
if (remap_pfn_range(vma,vma->vm_start, physical,vsize,vma->vm_page_prot))
{
return -EAGAIN;
}
printk(KERN_ALERT "Sucessfully memory mapped");
return 0;
}
--
Regards,
Sathishkumar D
http://flowersopenlab.weebly.com/
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