Messages in this thread | | | Date | Sun, 6 Jun 1999 20:19:52 +0200 | From | Martin Mares <> | Subject | Re: RFC: Devices, buses and hotplug |
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Hello,
> Allocating the entire device strikes me as extremely limiting.
I didn't say it's the only possibility :-)) Anyway, it's fine for most cases.
> parport already needs to share the same parallel port,
Think of parport as of a bus with virtual devices corresponding to the devices daisy-chained on the parport.
> and the stuff I > am interested in -- VGA and video drivers -- often wind up needing to > share the VGA ports. In order to support multiple VGA cards in a single > machine, I do this > > pci_disable_other_vga_card_io_regions() > pci_enable_my_vga_card_io_regions() > > { the fb driver does some VGA port I/O } > > pci_disable_my_vga_card_io_regions() > pci_enable_other_vga_card_io_regions()
VGA ports certainly cannot be handled as ordinary PCI I/O ports since they don't obey any sane rules. Support of multiple VGA cards is a nightmare and basically it's going to contain a lot of card-dependent code and be handled by an extra kernel module. No need to encumber the generic resource management stuff with this.
> This is definitely important, as one particular S3 card will report its > MMIO region as 32 MB instead of the correct 64 MB.
Yes, this is exactly the case where we need to relocate a PCI card even in a non-hotplug environment. Anyway, except for such cases we should avoid PCI relocation as otherwise we'd have to know about all non-standard host bridges.
> Slightly off topic: What about AGP? Is any work or planning going on > in that direction? I know it's compatible with PCI, but there don't > seem to be any constants in the kernel yet for accessing the new > configuration commands and such.
From the configuration point of view, AGP is identical to PCI. Maybe generic AGP access routines will appear one day, but for now I know of no driver needing it.
Have a nice fortnight -- Martin `MJ' Mares <mj@ucw.cz> http://atrey.karlin.mff.cuni.cz/~mj/ Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth "MIPS: Meaningless Indicator of Processor Speed."
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