Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751145AbVLOWXo (ORCPT ); Thu, 15 Dec 2005 17:23:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751152AbVLOWXo (ORCPT ); Thu, 15 Dec 2005 17:23:44 -0500 Received: from rtsoft3.corbina.net ([85.21.88.6]:48251 "EHLO buildserver.ru.mvista.com") by vger.kernel.org with ESMTP id S1751145AbVLOWXn (ORCPT ); Thu, 15 Dec 2005 17:23:43 -0500 Message-ID: <43A1ECE4.6010600@ru.mvista.com> Date: Fri, 16 Dec 2005 01:23:32 +0300 From: Vitaly Wool User-Agent: Mozilla Thunderbird 0.8 (Windows/20040913) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Greg KH CC: David Brownell , linux-kernel@vger.kernel.org, dpervushin@gmail.com, akpm@osdl.org, basicmark@yahoo.com, komal_shah802003@yahoo.com, stephen@streetfiresound.com, spi-devel-general@lists.sourceforge.net, Joachim_Jaeger@digi.com Subject: Re: [PATCH/RFC] SPI: add DMAUNSAFE analog to David Brownell's core References: <20051212182026.4e393d5a.vwool@ru.mvista.com> <20051214171842.GB30546@kroah.com> <43A05C32.3070501@ru.mvista.com> <200512141102.53599.david-b@pacbell.net> <43A1118E.9040608@ru.mvista.com> <20051215164444.GA14870@kroah.com> In-Reply-To: <20051215164444.GA14870@kroah.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1414 Lines: 44 Greg KH wrote: >On Thu, Dec 15, 2005 at 09:47:42AM +0300, Vitaly Wool wrote: > > >>David Brownell wrote: >> >> >> >>>No, "stupid drivers will suffer"; nothing new. Just observe >>>how the ads7846 touchscreen driver does small async transfers. >>> >>> >>> >>> >>One cannot allocate memory in interrupt context, so the way to go is >>allocating it on stack, thus the buffer is not DMA-safe. >>Making it DMA-safe in thread that does the very message processing is a >>good way of overcoming this. >>Using preallocated buffer is not a good way, since it may well be >>already used by another interrupt or not yet processed by the worker >>thread (or tasklet, or whatever). >> >> > >Yes it is a good way. That's the way USB currently works in the kernel, >and it works just fine. It keeps the rules simple and everyone knows >what needs to be done. > > Looking at my usbnet stuff, I can't share that opinion :-/ Are you really ready to lower the performance and quality of service just for approach uniformity? And, can you please point me out the examples of devices behind USB bus that need to write registers from an interrupt context? Vitaly - 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/