From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ahmed S. Darwish" Subject: Re: [PATCH try #3] Input/Joystick Driver: add support AD7142 joystick driver Date: Mon, 15 Oct 2007 20:27:43 +0200 Message-ID: <20071015182743.GA2529@Ahmed> References: <1192459625.6215.17.camel@roc-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: owner-linux-input@atrey.karlin.mff.cuni.cz List-Help: List-Owner: List-Post: List-Unsubscribe: To: Dmitry Torokhov Cc: bryan.wu@analog.com, Andrey Panin , Roel Kluin <12o3l@tiscali.nl>, linux-input@atrey.karlin.mff.cuni.cz, linux-joystick@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Jean Delvare List-Id: linux-input@vger.kernel.org On Mon, Oct 15, 2007 at 11:48:17AM -0400, Dmitry Torokhov wrote: > Hi Bryan, > > On 10/15/07, Bryan Wu wrote: > > + > > +static int ad7142_thread(void *nothing) > > +{ > > + do { > > + wait_for_completion(&ad7142_completion); > > + ad7142_decode(); > > + enable_irq(CONFIG_BFIN_JOYSTICK_IRQ_PFX); > > + } while (!kthread_should_stop()); > > + > > No, this is not going to work well: > - you at least need to reinitialize the completion before enabling > IRQ, otherwise you will spin in a very tight loop > - if noone would touch the joystick ad7142_clsoe would() block > infinitely because noone would signal the completion and > ad7142_thread() would never stop. > > Completion is just not a good abstraction here... Please use work > abstraction and possibly a separate workqueue. > Bryan, I'm very interested in the technical advantage of using a completion here. In my _not-experienced_ opinion, I remember completions was created mainly for "create_task, wait till task got finished, go on" case. Why using it in a different context while workqueues was created for a similar situation to ad7142 one (non-irq context bottom-half) ? Regards, -- Ahmed S. Darwish HomePage: http://darwish.07.googlepages.com Blog: http://darwish-07.blogspot.com