Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751017AbVK3V7Q (ORCPT ); Wed, 30 Nov 2005 16:59:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751036AbVK3V7Q (ORCPT ); Wed, 30 Nov 2005 16:59:16 -0500 Received: from streetfiresound.liquidweb.com ([64.91.233.29]:60830 "EHLO host.streetfiresound.liquidweb.com") by vger.kernel.org with ESMTP id S1750995AbVK3V7P (ORCPT ); Wed, 30 Nov 2005 16:59:15 -0500 Subject: Re: [PATCH 2.6-git] SPI core refresh From: Stephen Street Reply-To: stephen@streetfiresound.com To: David Brownell Cc: Vitaly Wool , linux-kernel@vger.kernel.org, dpervushin@gmail.com, akpm@osdl.org, greg@kroah.com, basicmark@yahoo.com, komal_shah802003@yahoo.com, spi-devel-general@lists.sourceforge.net, Joachim_Jaeger@digi.com In-Reply-To: <200511301336.38613.david-b@pacbell.net> References: <20051130195053.713ea9ef.vwool@ru.mvista.com> <200511301336.38613.david-b@pacbell.net> Content-Type: text/plain Organization: StreetFire Sound Labs Date: Wed, 30 Nov 2005 13:59:10 -0800 Message-Id: <1133387950.4528.16.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-16) Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - host.streetfiresound.liquidweb.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - streetfiresound.com X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 989 Lines: 22 On Wed, 2005-11-30 at 13:36 -0800, David Brownell wrote: > > - it is DMA-safe > > Which as I pointed out is incorrect. The core API (async) has always > been fully DMA-safe. And a **LOT** lower overhead than yours, which > allocates buffers behind the back of drivers, and encourages lots of > memcpy rather than just doing DMA directly to/from the buffers that > are provided by the SPI protocol drivers. Minimal (or no) core intervention on the DMA code path is a good thing. I need to fix some broken hardware with software and must to move 96 bytes from one SPI device to another on the same SPI bus every for 4ms. Needless memcpy's will cause substantial performance problems in my application. Thinner is definitely better. -Stephen - 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/