From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Subject: Re: [PATCH 3.9] Driver for 7-segment displays connected over GPIOs Date: Mon, 7 Jan 2013 18:40:22 +0100 Message-ID: <20130107184022.72b23aa9@skate> References: <1357576928-29133-1-git-send-email-thomas.petazzoni@free-electrons.com> <20130107164845.GA2911@kroah.com> <20130107180708.2ffc1540@skate> <20130107172340.GA32401@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130107172340.GA32401-U8xfFu+wG4EAvxtiuMwx3w@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: Greg Kroah-Hartman Cc: Lior Amsalem , Andrew Lunn , Jason Cooper , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org Dear Greg Kroah-Hartman, On Mon, 7 Jan 2013 09:23:40 -0800, Greg Kroah-Hartman wrote: > > Indeed, it can be done from userspace since we're just controlling > > GPIOs. Having a kernel driver allows to describe this device in the > > Device Tree, like all other devices, and have it "magically" appear, > > with a convenient user-space interface. > > Ok, that means you want to use the kernel-standard userspace interface > for displays, right? If so, why not use it? I thought we already > supported LCD displays already, isn't there an interface for it? Don't > create random magic sysfs files without really thinking about it. Well, the LCD interface is about outputting pixel into a video memory. Quite different from: echo 6 > /sys/[...]/gpio-7seg.1/value No? > > Not having a kernel driver means that gazillions of applications > > re-invent the same piece of code over and over again, have to hardcode > > the GPIO numbers for a given piece of hardware, while the kernel > > abstract all of this very nicely. > > That sounds like a wonderful use of a userspace library to do this > properly. Much like libusb does, right? > > I still think as this can be done in userspace, it probably should be. Understood. Patches discarded. Thanks, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com