Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932751AbaLBA2J (ORCPT ); Mon, 1 Dec 2014 19:28:09 -0500 Received: from arroyo.ext.ti.com ([192.94.94.40]:45957 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752934AbaLBA2G (ORCPT ); Mon, 1 Dec 2014 19:28:06 -0500 Date: Mon, 1 Dec 2014 18:27:59 -0600 From: Benoit Parrot To: Maxime Ripard CC: Alexandre Courbot , Pantelis Antoniou , Jiri Prchal , Linus Walleij , "linux-gpio@vger.kernel.org" , Linux Kernel Mailing List , "devicetree@vger.kernel.org" Subject: Re: [Patch v2 1/2] gpio: add GPIO hogging mechanism Message-ID: <20141202002758.GC24551@ti.com> References: <1416527684-19017-1-git-send-email-bparrot@ti.com> <1416527684-19017-2-git-send-email-bparrot@ti.com> <20141201163639.GI25249@lukather> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20141201163639.GI25249@lukather> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Maxime Ripard wrote on Mon [2014-Dec-01 17:36:39 +0100]: > Hi, > > On Fri, Nov 28, 2014 at 04:30:01PM +0900, Alexandre Courbot wrote: > > > +/** > > > + * do_gpio_hog - Given node is a GPIO hog configuration, handle it > > > + * @np: device node to get GPIO from > > > + * > > > + * This is only used by of_gpiochip_add to request/set GPIO initial > > > + * configuration. > > > + */ > > > +static int do_gpio_hog(struct device_node *np) > > > +{ > > > + struct gpio_desc *desc = NULL; > > > + int err; > > > + const char *name; > > > + enum gpio_lookup_flags lflags; > > > + enum gpiod_flags dflags; > > > + > > > + desc = of_get_gpio_hog(np, &name, &lflags, &dflags); > > > + if (!desc) > > > + return -ENOTSUPP; > > > + else if (IS_ERR(desc)) > > > + return PTR_ERR(desc); > > > + > > > + err = gpiod_request(desc, name); > > > > Using this function means that a GPIO chip module cannot be unloaded > > if it uses GPIO hogs. Is it the intended behavior? If not, please use > > gpiochip_request_own_desc() instead, and make sure to call > > gpiochip_free_own_desc() for each hog when the driver is unloaded. > > The only thing I'd like to have would be that the request here would > be non-exclusive, so that a later driver would still be allowed later > on to request that GPIO later on and manage it itself (ideally using > the usual gpiod_request function). I'll let Linus chime in on this. But the premise for the hogging mechanism is to have a mechanism to set GPIOs which do not need to be requested by any other entity. If a driver needs access to a specific GPIO then it should use the existing gpiolib API to request it and set it up. > > Maxime > > -- > Maxime Ripard, Free Electrons > Embedded Linux, Kernel and Android engineering > http://free-electrons.com Regards, Benoit -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/