Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263979AbUFSPBC (ORCPT ); Sat, 19 Jun 2004 11:01:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263972AbUFSPBC (ORCPT ); Sat, 19 Jun 2004 11:01:02 -0400 Received: from stat1.steeleye.com ([65.114.3.130]:17792 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S263944AbUFSPA7 (ORCPT ); Sat, 19 Jun 2004 11:00:59 -0400 Subject: Re: Proposal for new generic device API: dma_get_required_mask() From: James Bottomley To: Krzysztof Halasa Cc: Linux Kernel , SCSI Mailing List In-Reply-To: References: <1087481331.2210.27.camel@mulgrave> <1087523134.2210.97.camel@mulgrave> Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Mailer: Ximian Evolution 1.0.8 (1.0.8-9) Date: 19 Jun 2004 10:00:50 -0500 Message-Id: <1087657251.2162.49.camel@mulgrave> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1206 Lines: 27 On Fri, 2004-06-18 at 18:07, Krzysztof Halasa wrote: > James Bottomley writes: > I don't think so. We already have separate masks for coherent > and non-coherent mappings (in PCI API, and I'm told it's to be extended > to DMA API as well). And we need them. > > The problem is we're missing DMA masks for non-alloc calls (depending > on the platform) and thus that it isn't very reliable. Drivers which > need this are forced to bounce buffers themselves, and many of them > will not work on 64-bit platforms (as of ~ 2.6.0, I don't check that > regularly). And yes, we really need reliable masks for non-alloc > mappings. Could you elaborate on this? In the current scheme the coherent mask is for descriptor allocation (i.e. dma_alloc_coherent()) and the dma_mask represents the bus physical addresses to which the device can DMA directly; there's not much more the DMA API really does, what do you think is missing? James - 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/