On Jun 23, 2011, at 4:41 AM, Thor Lancelot Simon wrote: > 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.
Really? That seems unlikely.
