On Thu, Jun 23, 2011 at 03:36:25PM +0700, Robert Elz wrote: > Date: Wed, 22 Jun 2011 19:30:55 -0400 (EDT) > From: der Mouse <mo...@rodents-montreal.org> > Message-ID: <201106222330.taa28...@sparkle.rodents-montreal.org> > > | But the interface is much older than that, and, even if it's not > | codified, there's a lot of history behind the notion that userland > | alignment of write() buffers affects, at most, performance, to the > | point where I consider it part of the interface. > > Not on access to raw devices it isn't, and never was - what Erik Fair > said (Message-id: <5f005e6a-5441-4bec-bb3c-4a9b79584...@netbsd.org>) > was 100% correct - if you're using a raw device, it is up to the > application to meet whatever the requirements of that particular device > are, because one of the properties of raw devices is that they don't > do any kind of rebuffering of data (and the driver must not - that is > a part of the interface contract).
That doesn't seem like it can really be right. There are plenty of systems where devices cannot DMA from user addresses. Thor
