RE: [PATCH] hwmon/sensors: fix SENSORS_LM75 dependencies

Zhang, Rui
2014-01-07T14:05:08Z

> -----Original Message-----
> From: Eduardo Valentin [mailto:eduardo.valentin@ti.com]
> Sent: Tuesday, January 07, 2014 8:24 PM
> To: Jean Delvare
> Cc: Guenter Roeck; Randy Dunlap; Stephen Rothwell; linux-
> next@vger.kernel.org; linux-kernel@vger.kernel.org; Frodo Looijaard;
> lm-sensors@lm-sensors.org; Zhang, Rui; Eduardo Valentin; linux-
> pm@vger.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@infradead.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@infradead.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@ti.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@intel.com>
> Cc: linux-pm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.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