From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755329AbbAWOvh (ORCPT ); Fri, 23 Jan 2015 09:51:37 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:52767 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752488AbbAWOve (ORCPT ); Fri, 23 Jan 2015 09:51:34 -0500 From: "Rafael J. Wysocki" To: Heikki Krogerus Cc: Alexandre Courbot , Linus Walleij , "Rafael J. Wysocki" , Darren Hart , Arnd Bergmann , Andy Shevchenko , Mika Westerberg , "linux-gpio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , ACPI Devel Maling List Subject: Re: [RFC PATCH] gpio: support for GPIO forwarding Date: Fri, 23 Jan 2015 16:14:13 +0100 Message-ID: <4300012.3cqZ9mP0gj@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.16.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20150123112122.GD30522@kuha.fi.intel.com> References: <1418890998-23811-1-git-send-email-heikki.krogerus@linux.intel.com> <1564228.rcRekIyDUd@vostro.rjw.lan> <20150123112122.GD30522@kuha.fi.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, January 23, 2015 01:21:22 PM Heikki Krogerus wrote: > > --Nq2Wo0NMKNjxTN9z > Content-Type: text/plain; charset=iso-8859-1 > Content-Disposition: inline > Content-Transfer-Encoding: 8bit > > Hi guys, > > On Thu, Jan 22, 2015 at 05:14:22PM +0100, Rafael J. Wysocki wrote: > > On Thursday, January 22, 2015 11:57:55 AM Alexandre Courbot wrote: > > > If we decide to go ahead with the solution proposed by this patch for > > > practical reasons (which are good reasons indeed), I still have one > > > problem with its current form. > > > > > > As the discussion highlighted, this is an ACPI problem, so I'd very > > > much like it to be confined to the ACPI GPIO code, to be enabled only > > > when ACPI is, and to use function names that start with acpi_gpio. > > > > I can agree with that. > > > > > The current implementation leverages platform lookup, making said lookup > > > less efficient in the process and bringing confusion about its > > > purpose. Although the two processes are indeed similar, they are > > > separate things: one is a legitimate way to map GPIOs, the other is a > > > fixup for broken firmware. > > > > > > I suppose we all agree this is a hackish fix, so let's confine it as > > > much as we can. > > > > OK > > > > Heikki, any comments? > > I'm fine with that. > > That actually makes me think that we could then drop the lookup tables > completely and use device properties instead with the help of "generic > property" (attached): Which reminds me that I've lost track of this one. Can you please resend it and CC something like linux-acpi? Also I'm not sure what you mean by "drop the lookup tables completely". > We would just need to agree on the format how to describe a gpio > property, document it and of course convert the current users as > usual. The format could be something like this as an example (I'm > writing this out of my head so don't shoot me if you can see it would > not work. Just an example): > > static const u32 example_gpio[] = { , , }; > > static struct dev_gen_prop example_prop[] = > { > .type = DEV_PROP_U32, > .name = "gpio,", > .nval = 2, > .num = &example_gpio, > }, > { }, > }; > > static struct platform_device example_pdev = { > ... > .dev = { > .gen_prop = &example_prop, > }, > } > > > In gpiolib.c we would then, instead of going through the lookups, > simply ask for that property: > > ... > sprintf(propname, "gpio,%s", con_id); > device_property_read_u32_array(dev, propname, &val, 2); > ... > desc = gpio_to_desc(val[0]); > flags = val[1]; > ... > > > So this is just and idea. I think it would be relatively easy to > implement. What do you guys think? Well, I need some time to think about that. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.