send data packets to driver hard_xmit function

Hi everybody,
Iam writing PCI device driver for my custom board that does bus
master DMA data transfer.
I registered my device as network device using
register_netdev(); and brought up using $ ifconfig dev0 up with IP
address.I can ping to my device interface dev0.

Now, what I need is that I need to pass some user data from
application into my driver's netdev->hard_start_xmit function through
socket interface. The dev_hard_xmit(struct sk_buff *skb, struct
net_device *netdev) function has to receive skb_data from application
and fill the DMA buffer.once the DMA buffer is full I need to transfer
it to device.
DMA transfer through IOCTL works well.
Iam not clear in passing user data through socket interface. I
know that I have to create socket, bind socket to my device(IP)
interface. when I try to send data using sendto() function , it doesn't
works well. i.e it doesn't invoke my drivers hard_start_xmit function.
Any answers/suggestions would be welcome.

thanks
sara