Messages in this thread | | | Date | Fri, 13 Dec 2002 21:24:42 -0800 | From | Andrew Morton <> | Subject | Re: DMA from SCSI controller to PCI frame buffer memory. |
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Alan Cox wrote: > > On Fri, 2002-12-13 at 19:15, Jason Howard wrote: > > Hello All, > > > > I am wondering if the functionality exists in the Linux kernel to DMA > > from a SCSI controller directly into frame buffer memory of a PCI video > > card? Is there a standard method for this (similar to sendfile) or will > > it require some hacking? > > In theory you can mmap the frame buffer memory, then do O_DIRECT I/O > into it. In practice it will buffer (I hope it still does).
An O_DIRECT disk read into a mmapped device region will fail (if it doesn't, it'll oops ;)). O_DIRECT requires valid pages inside mem_map[].
See the `vma->vm_flags & VM_IO' test in get_user_pages(), and the VALID_PAGE() test in get_page_map().
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