Messages in this thread |  | | Subject | Re: PATCH: trident , pci_enable_device moved | From | (Eric W. Biederman) | Date | 27 Apr 2001 03:33:41 -0600 |
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Jeff Garzik <jgarzik@mandrakesoft.com> writes:
> Andres Salomon wrote: > > This is what I was told (it was only needed for secondary video > > devices). From that, I would expect that all video devices would > > need it, just in case they happened to be the second card. Am I > > missing some subtlety in some of the video driers/chipsets that > > wouldn't allow them to be used as a second video device (therefore > > not requiring pci_enable_device)? > > They do need pci_enable_device, both primary and secondary displays. > For the primary display its safe to call pci_enable_device. For > secondary displays, you have to first disable I/O decoding for all VGA > devices before you can enable a secondary display. You don't want more > than one device decoding the legacy VGA region at any one time. > > Some cards have the capability to relocate the VGA region, which is > nice. The bigger problem is initializing secondary displays; every > video card has a proprietary video BIOS initialization sequence that is > run by main BIOS on startup. You can either duplicate this sequence > with C code, which is sometimes difficult due to lack of docs or variety > of boards, or you can execute the video BIOS with an x86 emulator.
Note: With linuxBIOS (and some other embedded linux setups) even a primary display doesn't get initialized until you start linux so if you can properly initialize your display please do it.
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