From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 0C3FC6B003D for ; Fri, 11 Dec 2009 19:03:19 -0500 (EST) Message-ID: <4B22DD89.2020901@agilent.com> Date: Fri, 11 Dec 2009 16:02:17 -0800 From: Earl Chew MIME-Version: 1.0 Subject: Re: [PATCH 1/1] Userspace I/O (UIO): Add support for userspace DMA In-Reply-To: <1228379942.5092.14.camel@twins> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, hjk@linutronix.de, gregkh@suse.de, hugh , linux-mm , Thomas Gleixner List-ID: I'm taking another look at the changes that were submitted in http://lkml.org/lkml/2008/12/3/453 to see if they can be made more palatable. In http://lkml.org/lkml/2008/12/4/64 you wrote: > Why not create another special device that will give you DMA memory when > you mmap it? That would also allow you to obtain the physical address > without this utter horrid hack of writing it in the mmap'ed memory. > > /dev/uioN-dma would seem like a fine name for that. I understand the main objection was the hack to return the physical address of the allocated DMA buffer within the buffer itself amongst some other things. Your suggestion was to create /dev/uioN-dma for the purpose of allocating DMA memory. I'm having trouble figuring out how this would help to return the physical (bus) address of the DMA memory in a more elegant manner. What idea did you have for the userspace program to obtain the physical (bus) of the allocated DMA memory buffer? Earl -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org