title: how to get physical address of V4L2 DMA virtual address?
body: <p>I have a typical V4L2 driver that I use configured for memory mapped IO method. This driver hands off a virtual address to my user space app. All of this is working fine.</p>
  
  <p>I have another driver that expects as input a kernel physical address. I want to connect the output of the V4L2 driver to the input of this driver but it needs a physical address (this driver controls FPGA functionality).</p>
  
  <p>My understanding is that the kernel routine:  virt_to_phys() routine will NOT work with DMA allocated memory mapped addresses.  Is this true?  If so, how do I get the physical address from the DMA memory mapped V4L2 virtual address that was passed into user space?</p>
  
  <p>I am just hacking up a proof of concept thing here so hard coding some addresses is not an issue. This is the sole application running on a dedicated embedded platform.</p>
  
  <p>Thanks,
  -Andres </p>