Subject: Re: [PATCH] hwmon/sensors: fix SENSORS_LM75 dependencies

From: Zhang Rui <[email-masked]>
Date: Wed, 08 Jan 2014 10:02:53 +0800

On Tue, 2014-01-07 at 15:21 +0100, Jean Delvare wrote:
> Hi Eduardo,
> 
> On Tue, 7 Jan 2014 08:23:43 -0400, Eduardo Valentin wrote:
> > On 07-01-2014 08:04, Jean Delvare wrote:
> > > On Mon, 06 Jan 2014 18:26:34 -0800, Guenter Roeck wrote:
> > >> This needs to be addressed
> > >> in the thermal code, for example with dummy declarations if THERMAL=m but
> > >> SENSORS_LM75=y. The functions are already declared as dummies if THERMAL_OF=n.
> > > 
> > > This won't fly I'm afraid, the number of hwmon drivers affected will
> > > grow in the future and you certainly don't want to have to change the
> > > generic thermal code every time a new driver is added/converted.
> > 
> > Agreed
> > 
> > > 
> > > I've looked at the problem this morning and I will admit I do not even
> > > understand what the problem is. In Randy's config, CONFIG_THERMAL_OF=y
> > > so both thermal_zone_of_sensor_unregister and
> > > thermal_zone_of_sensor_register are built-in. SENSORS_LM75=y so the
> > > calls to these functions are built-in too. I just can't see how this
> > > can be a problem at link time. Can anyone enlighten me?
> > 
> > I believe the problem is more in the fact that THERMAL_OF is a bool, but
> > the way it is in thermal Kconfig, it will link to the thermal module, in
> > case CONFIG_THERMAL=m.
> 
> Doh. I've been looking at this for an hour and managed to miss
> that :( Thanks for explaining.
> 
> > Thus I am proposing the following,
> > which limits the user to have THERMAL_OF only as builtin and whenever
> > is selected, it will select THERMAL too. That is:
> > 
> > 
> > From b643aa260ed4f3514d1ca51b1ecbe4be7652a8d0 Mon Sep 17 00:00:00 2001
> > From: Eduardo Valentin <[email-masked]>
> > Date: Tue, 7 Jan 2014 08:04:02 -0400
> > Subject: [PATCH 1/1] thermal: fix compilation issue on CONFIG_THERMAL_OF
> >  dependencies
> > 
> > Users of API provided by THERMAL_OF config may suffer when
> > CONFIG_THERMAL=y, causing linking issues, such as:
> > 
> > drivers/built-in.o: In function `lm75_remove':
> > lm75.c:(.text+0x12bd8c): undefined reference to
> > `thermal_zone_of_sensor_unregister'
> > drivers/built-in.o: In function `lm75_probe':
> > lm75.c:(.text+0x12c123): undefined reference to
> > `thermal_zone_of_sensor_register'
> > 
> > Therefore, this patch limits the compilation build to always
> > have THERMAL=y, whenever THERMAL_OF=y. In this way, whenever
> > the API user is built, if THERMAL_OF=y, the build shall have
> > the full thermal support, otherwise, the thermal API will provide
> > stubs.
> > 
> > Cc: Zhang Rui <[email-masked]>
> > Cc: [email-masked]
> > Cc: [email-masked]
> > Signed-off-by: Eduardo Valentin <[email-masked]>
> > ---
> >  drivers/thermal/Kconfig | 29 ++++++++++++++++-------------
> >  1 file changed, 16 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> > index 58f98bd..dc315e9 100644
> > --- a/drivers/thermal/Kconfig
> > +++ b/drivers/thermal/Kconfig
> > @@ -29,19 +29,6 @@ config THERMAL_HWMON
> >  	  Say 'Y' here if you want all thermal sensors to
> >  	  have hwmon sysfs interface too.
> > 
> > -config THERMAL_OF
> > -	bool
> > -	prompt "APIs to parse thermal data out of device tree"
> > -	depends on OF
> > -	default y
> > -	help
> > -	  This options provides helpers to add the support to
> > -	  read and parse thermal data definitions out of the
> > -	  device tree blob.
> > -
> > -	  Say 'Y' here if you need to build thermal infrastructure
> > -	  based on device tree.
> > -
> >  choice
> >  	prompt "Default Thermal governor"
> >  	default THERMAL_DEFAULT_GOV_STEP_WISE
> > @@ -235,3 +222,19 @@ source "drivers/thermal/samsung/Kconfig"
> >  endmenu
> > 
> >  endif
> > +
> > +menuconfig THERMAL_OF
> > +	bool
> > +	prompt "APIs to parse thermal data out of device tree"
> > +	depends on OF
> > +	select THERMAL
> > +	default y
> > +	help
> > +	  This options enables DT thermal API which adds support to
> > +	  read and parse thermal data definitions out of the
> > +	  device tree blob. This option is mostly used by embedded
> > +	  thermal drivers.
> > +
> > +	  Say 'Y' here if you need to build thermal infrastructure
> > +	  based on device tree.
> > +
> 
> I suppose this works, however I believe there is value in allowing for
> modular building of as much code as possible.
> 
> I have an alternative proposal, which lets thermal be built as module,
> and hopefully also addresses the issue (I can't test...) The only
> drawback is that the same dependency must be added for every other
> hwmon driver which optionally uses THERMAL_OF.
> 
> From: Jean Delvare <[email-masked]>
> 
> Based on an earlier attempt by Randy Dunlap.
> 
> Fix SENSORS_LM75 dependencies to eliminate build errors:
> 
> drivers/built-in.o: In function `lm75_remove':
> lm75.c:(.text+0x12bd8c): undefined reference to `thermal_zone_of_sensor_unregister'
> drivers/built-in.o: In function `lm75_probe':
> lm75.c:(.text+0x12c123): undefined reference to `thermal_zone_of_sensor_register'
> 
> Add depends on THERMAL since that is what provides the
> register/unregister functions above, but only if THERMAL_OF was
> selected as this is an optional feature of the driver.
> 
> Signed-off-by: Jean Delvare <[email-masked]>
> Cc: Randy Dunlap <[email-masked]>
> Cc: Eduardo Valentin <[email-masked]>

Acked-by: Zhang Rui <[email-masked]>

thanks,
rui
> ---
>  drivers/hwmon/Kconfig |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- linux-3.13-rc7.orig/drivers/hwmon/Kconfig	2014-01-07 09:01:24.812848091 +0100
> +++ linux-3.13-rc7/drivers/hwmon/Kconfig	2014-01-07 15:19:11.039472329 +0100
> @@ -650,6 +650,7 @@ config SENSORS_LM73
>  config SENSORS_LM75
>  	tristate "National Semiconductor LM75 and compatibles"
>  	depends on I2C
> +	depends on THERMAL || !THERMAL_OF
>  	help
>  	  If you say yes here you get support for one common type of
>  	  temperature sensor chip, with models including:
> 
>