From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Walleij Subject: Re: [PATCH 3/3] gpio: mcp23s08: Add option to configure IRQ as active high Date: Fri, 28 Nov 2014 16:39:31 +0100 Message-ID: References: <1416213491-9775-1-git-send-email-alexander.stein@systec-electronic.com> <1416213491-9775-3-git-send-email-alexander.stein@systec-electronic.com> <3020714.NCVpEFcdBT@ws-stein> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <3020714.NCVpEFcdBT@ws-stein> Sender: linux-gpio-owner@vger.kernel.org To: Alexander Stein Cc: Rob Herring , Pawel Moll , "devicetree@vger.kernel.org" , "linux-gpio@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Thu, Nov 27, 2014 at 3:36 PM, Alexander Stein wrote: > On Thursday 27 November 2014 14:58:39, Linus Walleij wrote: >> Sorry too confused by this, can you explain? > > Sure. Until now ODR is cleared as reset default while INTPOL explicitly gets cleared. > So the INT output pin on the MCP23S17 is an active-low output pin which will trigger > an active-low interrupt. OK... I thought it was some kind of input line to the device. Now I get it, it is what is generated *out* of this device. Please state this in the bindings. > While this is useually great, as most interrupt pins are active low, our board design > requires an active-high output. OK I get it :) > You might wonder why I then also changed IRQF_TRIGGER_LOW to > IRQF_TRIGGER_HIGH for my board the interrupt line is actually active low. > This is due the fact that GIC only supports active high-interrupts (any other flag > results in request fail) but the microcontroller has a feature to inverse these interrupt triggers. Very convoluted, but common in electronics, OK, no problem. Yours, Linus Walleij