linux-kernel - RE: [PATCH] hwmon/sensors: fix SENSORS

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Date:	Tue, 7 Jan 2014 14:05:04 +0000
From:	"Zhang, Rui" <rui.zhang@...el.com>
To:	Eduardo Valentin <eduardo.valentin@...com>,
	Jean Delvare <khali@...ux-fr.org>
CC:	Guenter Roeck <linux@...ck-us.net>,
	Randy Dunlap <rdunlap@...radead.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Frodo Looijaard <frodol@....nl>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: RE: [PATCH] hwmon/sensors: fix SENSORS_LM75 dependencies



> -----Original Message-----
> From: Eduardo Valentin [mailto:eduardo.valentin@...com]
> Sent: Tuesday, January 07, 2014 8:24 PM
> To: Jean Delvare
> Cc: Guenter Roeck; Randy Dunlap; Stephen Rothwell; linux-
> next@...r.kernel.org; linux-kernel@...r.kernel.org; Frodo Looijaard;
> lm-sensors@...sensors.org; Zhang, Rui; Eduardo Valentin; linux-
> pm@...r.kernel.org
> Subject: Re: [PATCH] hwmon/sensors: fix SENSORS_LM75 dependencies
> Importance: High
> 
> On 07-01-2014 08:04, Jean Delvare wrote:
> > Hi Guenter, Randy,
> >
> > On Mon, 06 Jan 2014 18:26:34 -0800, Guenter Roeck wrote:
> >> On 01/06/2014 05:09 PM, Randy Dunlap wrote:
> >>> From: Randy Dunlap <rdunlap@...radead.org>
> >>>
> >>> 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_OF since that is what provides the
> >>> register/unregister functions above.
> >>>
> >>> Add depends on THERMAL since THERMAL is a tristate (while
> THERMAL_OF
> >>> is a bool) and SENSORS_LM75 (tristate) needs to be limited to
> >>> modular builds when THERMAL=m.
> >>>
> >>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> >>> ---
> >>>   drivers/hwmon/Kconfig |    2 ++
> >>>   1 file changed, 2 insertions(+)
> >>>
> >>> --- linux-next-20140106.orig/drivers/hwmon/Kconfig
> >>> +++ linux-next-20140106/drivers/hwmon/Kconfig
> >>> @@ -650,6 +650,8 @@ config SENSORS_LM73
> >>>   config SENSORS_LM75
> >>>   	tristate "National Semiconductor LM75 and compatibles"
> >>>   	depends on I2C
> >>> +	depends on THERMAL
> >>> +	depends on THERMAL_OF
> >>>   	help
> >>>   	  If you say yes here you get support for one common type
> of
> >>>   	  temperature sensor chip, with models including:
> >>>
> >>>
> >> NACK. The driver does not and must not depend on THERMAL.
> >
> > Correct.
> >
> >> 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. 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 <eduardo.valentin@...com>
> 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 <rui.zhang@...el.com>
> Cc: linux-pm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Eduardo Valentin <eduardo.valentin@...com>
> ---
>  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.
> +
> --
> 1.8.2.1.342.gfa7285d
> 
> Randy, can you please confirm if this fix the issue for you?
> 
The patch looks good to me, will apply it after it has been verified to fix the problem.
BTW, I've been thinking of make CONFIG_THERMAL a bool since long time ago, the only thing that blocks me is that Thermal subsystem needs to register a hwmon device for each thermal zone and CONFIG_HWMON is a tristate.

Thanks,
rui
> --
> You have got to be excited about what you are doing. (L. Lamport)
> 
> Eduardo Valentin

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