The HyperNews Linux KHG Discussion Pages

## Physical Address to Point DMA data to

  Forum: Device Drivers
  Date: Wed, 12 Nov 1997 16:13:46 GMT
  From: John Huggins <vmelinux@va.net>

Hello, We have a hardware device on the PCI bus, which we can set up to perform DMA transfers. Currently we are writing data to a dummy variable. It is very fast and desirable. Question: How can our driver obtain a physical address from the kernel virtual address so that the DMA device can write its set of data without fear of messing things up. We use "vremap" to map the PCI address of the PCI hardware to "kernel" space. Is there a way to get the physical address of a "kernel" address. Or is there a way to get the physical address of a "kalloc" memory chunk? Or do you all know a better way to let a DMA device know where to access memory? John Huggins VMELinux Project http://www.vmelinux.com/ vmelinux@va.net