From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: USB transfer_buffer allocations on 64bit systems Date: Wed, 7 Apr 2010 18:16:03 +0200 Message-ID: <20100407161603.GL30801@buzzloop.caiaq.de> References: <20100407153154.GC13425@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from buzzloop.caiaq.de (buzzloop.caiaq.de [212.112.241.133]) by alsa0.perex.cz (Postfix) with ESMTP id 7B988243B9 for ; Wed, 7 Apr 2010 18:16:07 +0200 (CEST) Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Alan Stern Cc: alsa-devel@alsa-project.org, linux-usb@vger.kernel.org, Greg KH , Greg KH , linux-kernel@vger.kernel.org, Pedro Ribeiro , akpm@linux-foundation.org List-Id: alsa-devel@alsa-project.org On Wed, Apr 07, 2010 at 11:55:19AM -0400, Alan Stern wrote: > On Wed, 7 Apr 2010, Greg KH wrote: > > > Alan, any objection to just using usb_buffer_alloc() for every driver? > > Or is that too much overhead? > > I don't know what the overhead is. But usb_buffer_alloc() requires the > caller to keep track of the buffer's DMA address, so it's not a simple > plug-in replacement. In addition, the consistent memory that > usb_buffer_alloc() provides is a scarce resource on some platforms. > > Writing new functions is the way to go. Ok, I'll write some dummies for usb_malloc() and usb_zalloc() which will just call kmalloc() with GFP_DMA32 for now. And while at it, usb_alloc_buffer() will be renamed to usb_alloc_consistent(). Then I'll try to clean up all existing drivers to use this new interface and follow the changes. In a next step, we should fine-tune when GFP_DMA32 is really needed. And I'll leave all occurances of usb_alloc_consistent() as they are now. Does that sound ok? Thanks, Daniel