From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: jgarzik and max-sectors: out of memory Date: Sat, 27 May 2006 15:49:31 -0400 Message-ID: <4478AD4B.5090404@rtr.ca> References: <4478AA6C.5070305@garzik.org> 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]:39302 "EHLO mail.rtr.ca") by vger.kernel.org with ESMTP id S1751580AbWE0Ttd (ORCPT ); Sat, 27 May 2006 15:49:33 -0400 In-Reply-To: <4478AA6C.5070305@garzik.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: "linux-ide@vger.kernel.org" , Tejun Heo , Alan Cox , Jens Axboe , Hannes Reinecke Jeff Garzik wrote: .. > Further -- someone with a long ATA memory correct me -- I think that we > can increase ATA_MAX_PRD beyond 256. Most DMA engines should just keep > chugging along, provided that we continue to respect the 64k IDE DMA > boundaries. MAX_PRD used to be equal to MAX_SECTORS, as that's the worst case scenario. The only real gotcha I remember from the original IDE driver, was that some (very few) controllers were buggy with handing of a sector_count of zero (256), so setting the limit to a slightly lower value prevented that from ever being a problem. That was in the days before the block layer could limit the segment count. I don't remember which chipsets had the bug; TRM290 was one, but that never really worked well anyway, and nobody other than myself seemed to have one of those cards. Mmm.. Possibly the Pacific Digital ADMA-100 here as well.. I can look that one up if I can find the old box full of cards/docs.. Cheers