Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757072Ab0DGR7m (ORCPT ); Wed, 7 Apr 2010 13:59:42 -0400 Received: from buzzloop.caiaq.de ([212.112.241.133]:38377 "EHLO buzzloop.caiaq.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752285Ab0DGR7l (ORCPT ); Wed, 7 Apr 2010 13:59:41 -0400 Date: Wed, 7 Apr 2010 19:59:35 +0200 From: Daniel Mack To: Takashi Iwai Cc: Alan Stern , Greg KH , linux-kernel@vger.kernel.org, Pedro Ribeiro , akpm@linux-foundation.org, Greg KH , alsa-devel@alsa-project.org, linux-usb@vger.kernel.org Subject: Re: USB transfer_buffer allocations on 64bit systems Message-ID: <20100407175935.GN30801@buzzloop.caiaq.de> References: <20100407153154.GC13425@kroah.com> <20100407161603.GL30801@buzzloop.caiaq.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1630 Lines: 42 On Wed, Apr 07, 2010 at 07:55:20PM +0200, Takashi Iwai wrote: > At Wed, 7 Apr 2010 18:16:03 +0200, > Daniel Mack wrote: > > > > 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. > > Can't we provide only zalloc() variant? Zero'ing doesn't cost much, > and the buffer allocation shouldn't be called too often. > > > And while at it, > > usb_alloc_buffer() will be renamed to usb_alloc_consistent(). > > Most of recent functions are named with "coherent". I agree to both points, will do so unless anyone has a harsh opinion about that. Another thing: I guess we don't need a corresponding free() function that just calls kfree(), right? Or should we introduce it now to be flexible for future extensions? Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/