From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mauro Carvalho Chehab Subject: Re: [RFC] What are the goals for the architecture of an in-kernel IR system? Date: Tue, 08 Dec 2009 13:49:01 -0200 Message-ID: <4B1E756D.2090908@redhat.com> References: <20091204220708.GD25669@core.coreip.homeip.net> <9e4733910912041628g5bedc9d2jbee3b0861aeb5511@mail.gmail.com> <1260070593.3236.6.camel@pc07.localdom.local> <20091206065512.GA14651@core.coreip.homeip.net> <4B1B99A5.2080903@redhat.com> <9e4733910912060952h4aad49dake8e8486acb6566bc@mail.gmail.com> <9e4733910912061323x22c618ccyf6edcee5b021cbe3@mail.gmail.com> <4B1D934E.7030103@redhat.com> <4B1E5DA3.7000206@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-media-owner@vger.kernel.org To: Krzysztof Halasa Cc: Jon Smirl , Dmitry Torokhov , hermann pitton , Christoph Bartelmus , awalls@radix.net, j@jannau.net, jarod@redhat.com, jarod@wilsonet.com, kraxel@redhat.com, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, superm1@ubuntu.com List-Id: linux-input@vger.kernel.org Krzysztof Halasa wrote: > Mauro Carvalho Chehab writes: > >> If you use a kfifo to store the event (space_or_mark, timestamp), >> the IRQ handler can return immediately, and a separate kernel thread >> can do the decode without needing to touch at the IRQ. > > But the decoding itself is a really simple thing, why complicate it? > There is no need for the kernel thread if the handler is fast (and it > is). The decoding of just one protocol may be fast, but having several decoders serialized (without kthreads, you're serializing the decoders) will possibly not be that fast. Also, you don't need wake the decoders kthreads for every event, but wait for some number of events to happen before waking it. For example, 16 pulse/space events correspond to 8 bits of data on most protocols, so you can wake the kthread only after 16 events for really simple decoders, or if a timeout event is detected. The number of events to wake may be customized per decoder. Cheers, Mauro.