From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932079AbcAHJnI (ORCPT ); Fri, 8 Jan 2016 04:43:08 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:42456 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750794AbcAHJnF (ORCPT ); Fri, 8 Jan 2016 04:43:05 -0500 Date: Fri, 8 Jan 2016 01:43:03 -0800 From: Christoph Hellwig To: "Steinar H. Gunderson" Cc: Christoph Hellwig , Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stern@rowland.harvard.edu Subject: Re: [PATCH] Add support for usbfs zerocopy. Message-ID: <20160108094303.GA9234@infradead.org> References: <20160106064949.GA14998@infradead.org> <20160106144512.GA21737@imap.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160106144512.GA21737@imap.gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 06, 2016 at 03:45:12PM +0100, Steinar H. Gunderson wrote: > On Tue, Jan 05, 2016 at 10:49:49PM -0800, Christoph Hellwig wrote: > > This is a completely broken usage of the mmap interface. if you use > > mmap on a device file you must use the actual mmap for the data > > transfer. > > Really? V4L does exactly the same thing, from what I can see. It's just a way > of allocating memory with specific properties, roughly similar to hugetlbfs. V4l is generally speaking never an example for good practices.