From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Likely Subject: Re: [PATCH] Add support for slave controllers plus sysfs entries for power management Date: Tue, 16 Feb 2010 15:07:28 -0700 Message-ID: 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 Tue, Feb 16, 2010 at 12:33 PM, 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. No, the model needs to be in place first. That means describing the model for spi_slave transfers. Does the driver need to turn around and respond mid-transfer? Does there need to be latency controls? How are protocol drivers interfaced with spi slave controllers (1 to 1, or 1 to many, how is the protocol selected)? I appreciate the work Ken is doing, but the patches posted so far abuse the spi_master model in a way I'm not willing to merge. I think spi_slave is a different enough thing that it warrants an entirely different core infrastructure (but I do reserve the right to have my mind changed). > 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. Your right, the realtime issues are separate, but I still need to see how spi_slave devices are intended to work, and what the strengths/limitations of the model are. g. ------------------------------------------------------------------------------ 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