Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753317AbaAZUoj (ORCPT ); Sun, 26 Jan 2014 15:44:39 -0500 Received: from mail.active-venture.com ([67.228.131.205]:56570 "EHLO mail.active-venture.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753215AbaAZUoi (ORCPT ); Sun, 26 Jan 2014 15:44:38 -0500 X-Originating-IP: 108.223.40.66 Message-ID: <52E573B6.9040903@roeck-us.net> Date: Sun, 26 Jan 2014 12:44:38 -0800 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Jean Delvare CC: LM Sensors , linux-kernel@vger.kernel.org, Mark Brown , Liam Girdwood , Wei Ni Subject: Re: lm90 driver no longer working on PCs in 3.13 References: <52E561D0.4040308@roeck-us.net> <20140126211357.6fa68909@endymion.delvare> In-Reply-To: <20140126211357.6fa68909@endymion.delvare> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jean, On 01/26/2014 12:13 PM, Jean Delvare wrote: > Hi Guenter, > > Adding Wei Ni to Cc, as he provided the commit which causes problem. > > On Sun, 26 Jan 2014 11:28:16 -0800, Guenter Roeck wrote: >> Hi, >> >> the lm90 driver is no longer working on PCs with the 3.13 kernel ... or at least not without >> special configuration. >> >> This is what I get if I try to instantiate a device on it (max6695): >> >> i2c 1-0018: Driver lm90 requests probe deferral >> i2c i2c-1: new_device: Instantiated device max6695 at 0x18 >> >> The regulator core always returns -EPROBE_DEFER if the platform does not support devicetree >> and if the regulator it is looking for does not exist. Since the driver now requires a mandatory >> regulator (commit 3e0f964f2ad - hwmon: (lm90) Add power control), and the regulator it requests >> does not exist on a PC, the result is not really surprising. I thought the regulator core would >> realize that it has to return a dummy regulator, but apparently that is not the case, or I don't >> know how to configure it. >> >> Any idea what I might need to do to get it working ? > > Me, I really don't know. I seem to remember I tested Wei's patch set on > an emulated ADM1032 chip and it was working fine. So maybe it depends > on the kernel configuration, or something changed on the regulator side > meanwhile. > The regulator code changed with 3.13; the dummy regulator no longer exists, and the functionality it provided is supposed to be handled automatically. But that only really works on devicetree based systems and otherwise returns -EPROBE_DEFER as mentioned above. Maybe there is some configuration option, or maybe something needs to be configured from user space. I found neither. In the first case, we should create a dependency for the LM90 driver; in the latter case, we would have to make sure that it is well documented (I'd grumble on that, though - it would result in never ending trouble for us, having to repeatedly explain how this is now supposed to work). Another possible fix would be to have the regulator core return -ENODEV instead of -EPROBE_DEFER on non-dt systems. No idea if this would be acceptable or even feasible. Guenter -- 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/