Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753860Ab1FKJpG (ORCPT ); Sat, 11 Jun 2011 05:45:06 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:55935 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753342Ab1FKJpD (ORCPT ); Sat, 11 Jun 2011 05:45:03 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=Q2UWug5/WBq7UCP6MXvEZ3NQx/cGvE9mlMTL1B3iieR4RcJPbhDmjXgGGzYlCFSLRH UZsLFkL7TP1dRS+qo6SqjHOK7mg8lOyDt01tVONhVnPFA1yfTnXIdIDhLYb+00qLM1J4 0Ks56xLSBi8ZipoOS+bLoF8oIee0cDSIBVk8E= Date: Sat, 11 Jun 2011 10:45:00 +0100 From: Catalin Marinas To: David Rientjes Cc: Russell King - ARM Linux , Linus Torvalds , Dmitry Eremin-Solenikov , Andrew Morton , KOSAKI Motohiro , tglx@linutronix.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mel@csn.ul.ie, kamezawa.hiroyu@jp.fujitsu.com, riel@redhat.com, pavel@ucw.cz Subject: Re: [PATCH] Make GFP_DMA allocations w/o ZONE_DMA emit a warning instead of failing Message-ID: <20110611094500.GA2356@debian.cable.virginmedia.net> References: <20110610004331.13672278.akpm@linux-foundation.org> <20110610091233.GJ24424@n2100.arm.linux.org.uk> <20110610185858.GN24424@n2100.arm.linux.org.uk> <20110610220748.GO24424@n2100.arm.linux.org.uk> <20110610222020.GP24424@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1477 Lines: 31 On Fri, Jun 10, 2011 at 03:30:35PM -0700, David Rientjes wrote: > On Fri, 10 Jun 2011, Russell King - ARM Linux wrote: > > So those platforms which don't have a DMA zone, don't have any problems > > with DMA, yet want to use the very same driver which does have a problem > > on ISA hardware have to also put up with a useless notification that > > their kernel might be broken? > > > > Are you offering to participate on other architectures mailing lists to > > answer all the resulting queries? > > It all depends on the wording of the "warning", it should make it clear > that this is not always an error condition and only affects certain types > of hardware which the user may or may not have. I think people will still be worried when they get a warning. And there are lots of platforms that don't need ZONE_DMA just because devices can access the full RAM. As Russell said, same drivers may be used on platforms that can actually do DMA only to certain areas of memory and require ZONE_DMA (there are several examples on ARM). If you want, you can add something like CONFIG_ARCH_HAS_ZONE_DMA across all the platforms that support ZONE_DMA and only get the warning if ZONE_DMA is available but not enabled. -- Catalin -- 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/