Hi Santhosh, I got this thing in dmesg: [10256.068664] driver_test:7114 map pfn RAM range req uncached-minus for 2f866000-2f867000, got write-back. I am writing some random numbers in mmapped memory. But I am not able to get it from the user space. Note: ( I have allocated memory via adc_dev.adcMemoryArea = (adcdata_t *) __get_free_pages(GFP_KERNEL, 1); ) On Sat, Nov 19, 2011 at 12:16 PM, santhosh kumars <karuna.linux@gmail.com> wrote:

hi, what is the exact error you are getting. thanks, santosh.

On Mon, Nov 14, 2011 at 10:26 AM, Sathishkumar Duraisamy <bewithsathish@gmail.com> wrote:

...

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/