From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: [PATCH] libata: Add pata_dma option so users can disable pata_dma as they can with old-ide Date: Fri, 22 Jun 2007 12:53:03 -0400 Message-ID: <467BFE6F.7050300@rtr.ca> References: <20070622144939.026ed6ac@the-village.bc.nu> <467BE435.5000001@rtr.ca> <20070622165221.2ce648f6@the-village.bc.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from rtr.ca ([64.26.128.89]:4106 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752676AbXFVQxH (ORCPT ); Fri, 22 Jun 2007 12:53:07 -0400 In-Reply-To: <20070622165221.2ce648f6@the-village.bc.nu> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Alan Cox Cc: jeff@garzik.org, davej@redhat.com, linux-ide@vger.kernel.org Alan Cox wrote: > On Fri, 22 Jun 2007 11:01:09 -0400 > Mark Lord wrote: > >> Alan Cox wrote: >>> Allow >>> >>> libata.pata_dma=0 >>> >>> to disable DMA (default is 1) >>> >>> SATA is unaffected as disabling DMA for SATA makes no sense at all. >>> >>> Signed-off-by: Alan Cox >> Alan, >> >> Should we really be piling up like this on global boot/module options >> rather than run-time flags on individual channels/devices ? >> >> I can imagine systems with internal notebook drives that want dma=1, >> plus Cardbus CF devices that require dma=0. >> >> With a single global flag, how does one do that? > > We need proper tuning as well but there is huge value (with distro hat > on especially) in a single "try this to get it installed and then we can > debug it" button. Same with the old IDE. Trying to guide users through > selecting specific channels/devices is going to be painful. I want > something that I can tell people to get them 'off the ground' and work > with them to sort the rest. Oh for sure. I'm just thinking that some form of on-the-fly tunable would be of even greater value here, in addition to the boot/load default flag. I think a /sys/ "dma" attribute (pick a name) might be most appropriate, or we just just implement HDIO_[GS]ET_DMA as a simpler/lazier mechanism. Cheers