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/