From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailhost.informatik.uni-hamburg.de ([134.100.9.70]:50080 "EHLO mailhost.informatik.uni-hamburg.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753431AbaBFVf4 (ORCPT ); Thu, 6 Feb 2014 16:35:56 -0500 Message-ID: <52F400D7.7050204@metafoo.de> Date: Thu, 06 Feb 2014 22:38:31 +0100 From: Lars-Peter Clausen MIME-Version: 1.0 To: Alessandro Rubini CC: john3909@gmail.com, linux-iio@vger.kernel.org, broonie@kernel.org, flatmax@flatmax.org Subject: Re: DMA sampling and IIO References: <52F3F84F.5040001@metafoo.de> <52F35C5B.7080409@metafoo.de> <20140206205327.GA11958@mail.gnudd.com> <20140206211637.GA14525@mail.gnudd.com> In-Reply-To: <20140206211637.GA14525@mail.gnudd.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 02/06/2014 10:16 PM, Alessandro Rubini wrote: >>> ZIO already supports dma. And mmaping the buffer from user space. It >>> is in the design since inception, and in the code since Feb 2012 (git >>> log says). >> >> I know. And I did study the ZIO DMA code (among other things), >> before I implemented the IIO DMA code. As you might remember from >> our last discussion, my preference is to add the features that are >> in ZIO but not in IIO to IIO and then ditch ZIO instead of having >> two frameworks for the class of devices. > > I remember. And we both know that the class of devices that ZIO already > supports cannot be supported by IIO, unless many incompatible changes > are made (sub-nanosecond timestamps, symmetric input and output, > hot-swap of buffer and trigger type, ...). > I still don't see why it is necessary to make incompatible changes to IIO to support this. There is nothing wrong with extending the API, while staying backwards compatible. > I'm happy all accelerometers have the same interface to user space, > this is definitely useful. But that's clearly not the same class of > devices. > >> and then ditch ZIO > > How can you "ditch" something you don't use? Or is your employer > currently using zio while helping iio catch up? I meant in general. > > Our users will not stop using it, despite your desire, because it > already serves them pretty well: 100MS ADC, with DMA and mmap, all > sysfs-based, completely run-time configurable, and v2.6.24..v3.12 (13 > untested yet). I have no desire to stop anybody from stopping using ZIO. But my recommendation is to work towards a unified framework. The sooner the switch is made the easier the migration path will be. I think we have systems with 4x 250MS ADCs also doing DMA and mmap and streaming over the network[1]. All with IIO, so again, there _is_ a huge overlap of the classes of devices supported by both IIO and ZIO. -Lars [1] https://wiki.analog.com/resources/fpga/xilinx/fmc/ad-fmcjesdadc1-ebz