From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754821Ab2LKUtO (ORCPT ); Tue, 11 Dec 2012 15:49:14 -0500 Received: from avon.wwwdotorg.org ([70.85.31.133]:33597 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753389Ab2LKUtN (ORCPT ); Tue, 11 Dec 2012 15:49:13 -0500 Message-ID: <50C79C41.8070305@wwwdotorg.org> Date: Tue, 11 Dec 2012 13:49:05 -0700 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Linus Walleij CC: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Stephen Warren , Anmar Oueja , Linus Walleij Subject: Re: [PATCH 2/2] pinctrl: skip deferral of hogs References: <1355232965-16596-1-git-send-email-linus.walleij@stericsson.com> In-Reply-To: <1355232965-16596-1-git-send-email-linus.walleij@stericsson.com> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/11/2012 06:36 AM, Linus Walleij wrote: > From: Linus Walleij > > Up until now, as hogs were always taken at the end of the > pin control device registration, it didn't cause any problem. > But when starting to hog pins from the device core it will > cause deferral of the pin controller device itself since the > default pin fetch is done *before* the device probes, so > let's fix this annoyance (which is also aesthetically ugly). I guess this is OK, although I can't quite get over the feeling of it being a bit of a hack. The issue is IIUC that the driver core is going to call pinctrl_get() for any device before it's probed, and if it succeeds it will select the default state, but this patch deliberately fails the pinctrl_get() for a pin controller, and hence relies on pinctrl_register() making a second attempt at pinctrl_get(), and also activating the default state there. That's a bit of duplication and rather asymmetric. That all said, I don't really see what we can do better, so I won't object! Oh, one comment on the patch. It returns -ENODEV as soon as any hog is seen. Just in case someone does something wierd, shouldn't it accumulate the "worst-case" return value and not return early? Consider a pin controller whose mapping table entries contain both hogs, /and/ entries that use a different pin controller. That's a little contrived, but trivial to actually do. As such, I think we want something more like: ret = 0 for every mapping table entry: if can't find pinctrl device: if map entry is a hog: # Requiring defer is a worst case, so defer the return! ret = -ENODEV else: # This is worst-case, so can return now return -EPROBE_DEFER if ret: cleanup return ret That way, if a mapping table entry requiring defer comes after a hog, we'll still return the correct value.