From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean Delvare Subject: Re: Dependency chain of new thermal driver Date: Tue, 18 Mar 2008 10:11:33 +0100 Message-ID: <20080318101133.525ecca0@hyperion.delvare> References: <20080316155659.7ab2446d@hyperion.delvare> <200803180131.30662.lenb@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from smtp-102-tuesday.nerim.net ([62.4.16.102]:54635 "EHLO kraid.nerim.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751530AbYCRJLg (ORCPT ); Tue, 18 Mar 2008 05:11:36 -0400 In-Reply-To: <200803180131.30662.lenb@kernel.org> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Len Brown Cc: "Zhang, Rui" , LM Sensors , linux-acpi@vger.kernel.org Hi Len, On Tue, 18 Mar 2008 01:31:30 -0400, Len Brown wrote: > On Sunday 16 March 2008, Jean Delvare wrote: > > Hi Rui, > > > > I am testing your new thermal driver and I am not very happy with the > > dependencies introduced by this driver. The ACPI thermal driver selects > > the generic thermal driver, which in turn selects the hwmon base > > module. As the generic thermal driver's configuration option is a > > boolean, this means that as soon as one selects the ACPI thermal driver > > (built-in or modular), the hwmon thermal driver has to be built into > > the kernel. This is a problem especially when both the ACPI_THERMAL and > > THERMAL options default to y. > > > > I fail to see why we are using select at all. The ACPI thermal driver > > clearly works without the generic thermal driver (even though the > > generic interface is preferred now.) Likewise, the generic thermal > > interface driver doesn't need the hwmon base module to work; the hwmon > > interface is only an extension, so it should be possible to build the > > generic thermal driver without hwmon support. On top of that, I really > > would like to be able to build the generic thermal driver as a module. > > > > One of the reasons why I would like this to change is this bug: > > https://bugzilla.redhat.com/show_bug.cgi?id=437637 > > http://bugzilla.kernel.org/show_bug.cgi?id=10259 > > (At the moment I think both reports are the exact same bug.) > > > > We will have to fix this bug of course (not sure how...) but the fact > > that the users can't temporarily remove the generic thermal driver is a > > problem both for bug investigation and for working around the bug until > > it's fixed. I really would like to be able to tell the user "rmmod this > > module until we come up with a fix", but right now I can't. > > > > A more modular setup would give us much more flexibility both at build > > time and when bugs are reported. Please think about it. > > You are absolutely right -- this is gone from 2.6.25, > lets get it right in 2.6.26. Great, thanks. > BTW. speaking of 2.6.26.... > the patch below might become helpful. For it would > be nice if at build-time we could just have hwmon_device_register() > fail, rather than put a bunch of #ifdef HWMON in our code. > > thanks, > -Len > > Signed-off-by: Len Brown > > diff --git a/include/linux/hwmon.h b/include/linux/hwmon.h > index 6b6ee70..68968cc 100644 > --- a/include/linux/hwmon.h > +++ b/include/linux/hwmon.h > @@ -16,9 +16,13 @@ > > #include > > +#ifdef CONFIG_HWMON > struct device *hwmon_device_register(struct device *dev); > - > void hwmon_device_unregister(struct device *dev); > +#else > +static struct device *hwmon_device_register(struct device *dev) { return ERR_PTR(-ENODEV); }; > +static void hwmon_device_unregister(struct device *dev) { return; }; > +#endif > > /* Scale user input to sensible values */ > static inline int SENSORS_LIMIT(long value, long low, long high) I'm not sure it's such a good idea. Registering a hwmon device is not only about calling hwmon_device_register(), it's also about creating all the sysfs attribute files and initializing everything that's needed for these files. There's already one driver which optionally registers a hwmon device (drivers/input/touchscreen/ads7846.c) and looking at the code, the patch above wouldn't really help. I think it only makes sense to handle the conditional in if (almost) everything can be handled there and it is transparent to the drivers. Otherwise I'd say it's not worth it, as we will still need #ifdefs in the driver code. -- Jean Delvare