From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Walleij Subject: Re: Active low GPIOs (was [PATCH v1 1/4] i2c: mux: Add i2c-arbitrator 'mux' driver) Date: Fri, 15 Feb 2013 21:58:13 +0100 Message-ID: References: <511D7EF7.9000803@wwwdotorg.org> <511E9DA8.70207@wwwdotorg.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <511E9DA8.70207-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Stephen Warren Cc: linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Daniel Kurtz , Wolfram Sang , "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Lee Jones , Guenter Roeck , Stephen Warren , Ben Dooks , u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, Chris Ball , Grant Grundler , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Rob Herring , Jean Delvare , Alexandre Courbot , "Ben Dooks (embedded platforms)" , Girish Shivananjappa , "bhushan.r" , Naveen Krishna Chatradhi , "sreekumar.c" , Mark Brown , linux-kernel-u79uwXL29Tb/PtFMR13I2A@public.gmane.org List-Id: devicetree@vger.kernel.org On Fri, Feb 15, 2013 at 9:42 PM, Stephen Warren wrote: > On 02/15/2013 01:34 PM, Linus Walleij wrote: >> 0xca000000 + 4 is just the second 32bit word in the system >> controller. This address range and that very word is used >> for various stuff, so it's not like a general-purpose GPIO >> or anything, it's just that one pin being readable throgh that >> very bit. > > Surely a GPIO is exactly what that is... > > It might be annoying to create a GPIO controller driver for just that, > but that seems like the simplest way to implement that HW from a device > tree perspective. With DT, it'd be painful to plug in that board > callback into the platform data there. Yeah well, I'll get to it sooner or later. I have seen cases of cherry-picked registers being routed to one driver etc (like an MFD device) but this is the first instance where we need to cherry-pick individual bits over to a separate driver. This will be a 1-bit, input-only gpio pin, npins = 1.... But hey, they buils spaceships for just one person so why not :-) Yours, Linus Walleij