Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758180Ab0DHAfg (ORCPT ); Wed, 7 Apr 2010 20:35:36 -0400 Received: from kroah.org ([198.145.64.141]:44207 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756371Ab0DHAff (ORCPT ); Wed, 7 Apr 2010 20:35:35 -0400 Date: Wed, 7 Apr 2010 17:33:13 -0700 From: Greg KH To: Alan Stern Cc: Takashi Iwai , Daniel Mack , 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: <20100408003313.GE4365@kroah.com> References: 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: 1826 Lines: 52 On Wed, Apr 07, 2010 at 03:13:11PM -0400, Alan Stern wrote: > On Wed, 7 Apr 2010, Takashi Iwai wrote: > > > > 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. > > Linus specifically requested us to avoid using kzalloc in usbfs. I > can't find the message in the email archives, but Greg KH should be > able to confirm it. > > As long as we're imitating kmalloc for one use, we might as well make > it available to all. > > > > And while at it, > > > usb_alloc_buffer() will be renamed to usb_alloc_consistent(). > > > > Most of recent functions are named with "coherent". > > Yes, the terminology got a little confused between the PCI and DMA > realms. I agree, "coherent" is better. > > BTW, although some EHCI controllers may support 64-bit DMA, the driver > contains this: > > if (HCC_64BIT_ADDR(hcc_params)) { > ehci_writel(ehci, 0, &ehci->regs->segment); > #if 0 > // this is deeply broken on almost all architectures > if (!dma_set_mask(hcd->self.controller, DMA_BIT_MASK(64))) > ehci_info(ehci, "enabled 64bit DMA\n"); > #endif > } > > I don't know if the comment is still true, but until the "#if 0" is > removed, ehci-hcd won't make use of 64-bit DMA. I think someone tried to remove it recently, but I wouldn't let them :) What a mess, hopefully xhci will just take over and save the world from this whole thing... thanks, greg k-h -- 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/