#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <stdlib.h>
#include <sys/mman.h>


struct mem_ioctl_data {
    unsigned long requested_size;
    unsigned long start_of_vma;
    unsigned long return_offset;
};

void * dma_malloc(unsigned int size)
{
    int fd = -1;
    unsigned int retval;
    int mmap_size;
    struct mem_ioctl_data mid;
    void * mmaprv;

    printf("\ndma_malloc called with size %u\n", size);

	if ((fd = open("/dev/my_module", O_RDWR)) < 0)
	{
		perror("open failed for /dev/my_module");
		return NULL;
	} else {
		//printf("\nopen succeeded\n");
	}

    mmap_size = (size/4096) + 1;

    printf("\nmmap_size = 0x%x\n", mmap_size);

    mmaprv = mmap(0, mmap_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

    if(mmaprv == MAP_FAILED)
    {
        printf("\nmmap failed\n");
        perror("mmap failure");
        return NULL;
    } else {
        printf("\nmmap succeeded mmaprv = 0x%p\n", mmaprv);
    }

    mid.requested_size = size;
    mid.start_of_vma   = (unsigned long)mmaprv;
    mid.return_offset  = 0xffffffff;

    retval = ioctl(fd, 1, &mid);
    if(retval)
    {
        perror("ioctl failed");
        return NULL;
    } else {
        printf("\nioctl succeeded\n");
    }

    if(mid.return_offset == 0xffffffff)
    {
        printf("\nmid.return_offset = 0x%lx\n", mid.return_offset);
        return NULL;
    }

    printf("\nmid.return_offset = 0x%lx\n", mid.return_offset);
    return (void *)(mmaprv + mid.return_offset);
}

int main(int argc, char * argv[])
{
    unsigned int size;
    char *cptr;
    void * ptr;

    printf("\nEnter the size of allocation ...\n");
    while (scanf("%u", &size))
    {
        printf("\nSize asked is %u\n", size);
        ptr = dma_malloc(size);
        if (ptr == NULL)
        {
            printf("\ndma_malloc failed for size %d ptr = 0x%p\n\n", size, ptr);
            return 0;
        } else {
            printf("\ndma_malloc succeeded for size %d ptr = 0x%p\n\n", size, ptr);
        }

        cptr = (char *)ptr;

        /*
         * This should print the signature that we wrote to the kmalloc'ed 
         * area in the driver
         */
        printf("\nptr = 0x%lx\n", *(unsigned long *)ptr);
    }

    return 0;
}