Messages in this thread | | | Subject | Re: DMA from SCSI controller to PCI frame buffer memory. | From | Jason Howard <> | Date | 14 Dec 2002 12:29:54 -0800 |
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> 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). One of the > problems is that there are huge lists of PCI->AGP DMA errata in > chipsets.
I am not accessing the AGP bus as my frame buffer is located on the PCI bus. 00:08.0 Multimedia video controller: Unknown device f1d0:efac Subsystem: Unknown device f1d0:efac Flags: bus master, stepping, medium devsel, latency 64, IRQ 10 Memory at f4000000 (32-bit, non-prefetchable) [size=4K] Memory at f6000000 (32-bit, prefetchable) [size=16M] (I am working with the second memory address)
Any recommendations on where to start hacking? Would it be a good idea to add O_DIRECT to a mmaped PCI space? The kernel should not be doing any buffering whatsoever, as we will be coming close to filling the pci bus up with transfers from direct disk->fb already. (We are already doing buffering on the FB card as well)
Jason -- Jason Howard
Professional: SpectSoft, LLC http://www.spectsoft.com jason@spectsoft.com Phone: +1.209.847.7812 Fax: +1.209.847.7859 Personal: http://www.psinux.org jason@psinux.org Cell: +1.209.968.1289 Text Message: jasonsphone@psinux.org
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