Messages in this thread |  | | Date | Fri, 17 Nov 2000 12:00:18 -0500 | From | Jeff Garzik <> | Subject | Re: VGA PCI IO port reservations |
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Russell King wrote: > > Brian Gerst writes: > > This is an artifact from the ISA 10-bit IO bus. Many ISA cards do not > > decode all 16 address bits so you get aliases of the 0x100-0x3ff region > > throughout IO space. PCI cards should only use the first 256 ports of > > any 1k block to avoid aliases unless they claim the base alias. For > > example, all the xxe8 addresses for the S3 are aliases of 0x02e8 to an > > ISA card. Video cards are an exception to the general rule because they > > have to support all the legacy VGA crap. > > No. All xxe8 addresses access specific registers. For example: > > 0x9ea8 is the drawing command > 0xa2e8 is the background colour register > 0xa6e8 is the foreground colour register > > So, as you see they aren't aliases.
Oh yeah, if you are writing for S3 specifically, you can do 100% MMIO, and simply turn off all I/O decoding. Check out Keith Packard's kdrive/s3trio in the XFree86 tree...
Jeff
-- Jeff Garzik | Building 1024 | The chief enemy of creativity is "good" sense MandrakeSoft | -- Picasso - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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