From mboxrd@z Thu Jan 1 00:00:00 1970 From: jassi brar Subject: Re: [PATCH] Add support for slave controllers plus sysfs entries for power management Date: Wed, 17 Feb 2010 10:43:12 +0900 Message-ID: <1b68c6791002161743w52da3a4h128b59c42e0602dc@mail.gmail.com> References: <1261170416.10785.5.camel@ubuntu-vmware> <63386a3d1002141520p7cf33256vd8d6f7c23f61b0fe@mail.gmail.com> <1b68c6791002141737l6211c88dy79c762a3761cc93c@mail.gmail.com> <63386a3d1002161133k501e51f4xf4e94a307cb4fcf5@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: spi mailing list , Ken Mills To: Linus Walleij Return-path: In-Reply-To: <63386a3d1002161133k501e51f4xf4e94a307cb4fcf5-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org On Wed, Feb 17, 2010 at 4:33 AM, Linus Walleij wrote: > 2010/2/15 jassi brar : > >> I don't think adding SPI_SLAVE support is just a matter of providing >> additional callbacks and structures, as is pointed out in this thread.... >> http://www.mail-archive.com/spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org/msg00368.html > > You mean that the responsiveness / control of latencies is the other thing > that's needed? Yep so it is. But getting the infrastructure in place doesn't > hurt because this is something many people (including self) need and Ken > over at Intel is the only one actually doing something about it. > > Getting SPI slaves to actually work by spawning their worker threads as > realtime under that patchset is of course a larger issue. One does not > exclude the other tho. I tend to resonate with Ned Forrester's concerns and Grant Likely already has clarified my point. As a further note, it *seems* someone just needs a way to test his SPI controller's SLAVE mode(I used to do that with much lesser changes to the SPI stack). Or I will be interested to know (to the extent your privilege to disclose extends) which device running a full fledged non-real time OS(Linux) needs to work as a SPI slave? I have been supporting Samsung's SPI drivers internally for quite some time now and am yet to come across one usage of it's SLAVE mode. Also, it's only intuitive that 'chips'(with minimal f/w, fixed functionality and bounded delays) run as SPI SLAVE and devices(with multiple processes and indeterminate latencies) as MASTER. So, I am not excited about (*coughs*) seeing SPI SLAVE support implemented without (a) real need for it (b) properly thought out architecture and not just a workaround. regards. ------------------------------------------------------------------------------ SOLARIS 10 is the OS for Data Centers - provides features such as DTrace, Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW http://p.sf.net/sfu/solaris-dev2dev