Messages in this thread | | | Date | Tue, 13 Dec 2011 15:47:01 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86: Split off mem*io functions |
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On 12/13/2011 02:58 PM, Linus Torvalds wrote: > > - some devices (for example, traditional CGA/VGA) read and write to > different banks and bit modes, so a "read-mask-write" operation just > does not work at all. You have to do pure writes when copying to such > a destination. Afaik, none of our *current* memory copies do this for > partial words, but it's an example of something that is valid (and > sometimes done) in memcpy to avoid unaligned stores, for example. >
VGA is even weirder: in some modes (which noone in their sane mind use) you can make it do operations versus an internal buffer. The catch is that the internal buffer is only 8 bits wide, so anything other than byte writes will fail in the extreme in those modes.
-hpa
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