linux-kernel - Re: i8k: move driver from char to hwmon

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Date:	Wed, 22 Apr 2015 10:42:39 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Jean Delvare <jdelvare@...e.de>
Cc:	Guenter Roeck <linux@...ck-us.net>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Steven Honeyman <stevenhoneyman@...il.com>,
	Valdis.Kletnieks@...edu,
	Jochen Eisinger <jochen@...guin-breeder.org>,
	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org
Subject: Re: i8k: move driver from char to hwmon

On Wednesday 22 April 2015 10:23:04 Jean Delvare wrote:
> On Sun, 22 Feb 2015 10:11:16 -0800, Guenter Roeck wrote:
> > On 02/22/2015 09:44 AM, Pali Rohár wrote:
> > > What about CONFIG_DELLDIAG (or DELLSMM or CONFIG_SENSORS_*) for
> > > mandatory core & hwmon code and (keep existing) CONFIG_I8K for
> > > /proc/i8k?
> > 
> > One option might be to leave CONFIG_I8K more or less alone
> > (it is in arch/x86/Kconfig anyway, which is odd by itself),
> > but add something like
> > 	select SENSORS_DELL
> > 	select I8K_PROC
> > to it. Then add new config options SENSORS_DELL and
> > I8K_PROC to drivers/hwmon/Kconfig.
> 
> On a related note...
> 
> Changing Kconfig symbol names is allowed, it has happened a lot in the
> past, although we should make it the least painful possible for the
> users.
> 
> I thought about it earlier as I considered several times the
> possibility to rename all CONFIG_SENSORS_* symbols to CONFIG_HWMON_*
> for consistency. I never actually took the time to do it, but here's
> how I would do it, taking the lm75 driver as an example.
> 
> As a first step, I would introduce a hidden symbol that would be
> selected automatically by the existing symbol:
> 
>  drivers/hwmon/Kconfig  |    4 ++++
>  drivers/hwmon/Makefile |    2 +-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> --- linux-4.1-rc0.orig/drivers/hwmon/Kconfig	2015-04-22 09:54:21.965974944 +0200
> +++ linux-4.1-rc0/drivers/hwmon/Kconfig	2015-04-22 10:10:16.974551936 +0200
> @@ -909,10 +909,14 @@ config SENSORS_LM73
>  	  This driver can also be built as a module.  If so, the module
>  	  will be called lm73.
>  
> +config HWMON_LM75
> +	tristate
> +
>  config SENSORS_LM75
>  	tristate "National Semiconductor LM75 and compatibles"
>  	depends on I2C
>  	depends on THERMAL || !THERMAL_OF
> +	select HWMON_LM75
>  	help
>  	  If you say yes here you get support for one common type of
>  	  temperature sensor chip, with models including:
> --- linux-4.1-rc0.orig/drivers/hwmon/Makefile	2015-04-22 09:54:21.965974944 +0200
> +++ linux-4.1-rc0/drivers/hwmon/Makefile	2015-04-22 10:09:03.712048849 +0200
> @@ -85,7 +85,7 @@ obj-$(CONFIG_SENSORS_LINEAGE)	+= lineage
>  obj-$(CONFIG_SENSORS_LM63)	+= lm63.o
>  obj-$(CONFIG_SENSORS_LM70)	+= lm70.o
>  obj-$(CONFIG_SENSORS_LM73)	+= lm73.o
> -obj-$(CONFIG_SENSORS_LM75)	+= lm75.o
> +obj-$(CONFIG_HWMON_LM75)	+= lm75.o
>  obj-$(CONFIG_SENSORS_LM77)	+= lm77.o
>  obj-$(CONFIG_SENSORS_LM78)	+= lm78.o
>  obj-$(CONFIG_SENSORS_LM80)	+= lm80.o
> 
> Running "make oldconfig" after that silently selects the new symbol as
> needed:
> 
> --- .config.old	2015-04-20 10:16:42.645359313 +0200
> +++ .config	2015-04-22 10:09:09.358164599 +0200
> @@ -2805,6 +2805,7 @@
>  CONFIG_SENSORS_LM63=m
>  # CONFIG_SENSORS_LM70 is not set
>  CONFIG_SENSORS_LM73=m
> +CONFIG_HWMON_LM75=m
>  CONFIG_SENSORS_LM75=m
>  CONFIG_SENSORS_LM77=m
>  CONFIG_SENSORS_LM78=m
> 
> Then I would let several kernel versions pass. After a year maybe, or 5
> kernel versions, we could get rid of the original symbol:
> 
>  drivers/hwmon/Kconfig |    4 ----
>  1 file changed, 4 deletions(-)
> 
> --- linux-4.1-rc0.orig/drivers/hwmon/Kconfig	2015-04-22 10:08:39.017542771 +0200
> +++ linux-4.1-rc0/drivers/hwmon/Kconfig	2015-04-22 10:09:57.376149603 +0200
> @@ -910,13 +910,9 @@ config SENSORS_LM73
>  	  will be called lm73.
>  
>  config HWMON_LM75
> -	tristate
> -
> -config SENSORS_LM75
>  	tristate "National Semiconductor LM75 and compatibles"
>  	depends on I2C
>  	depends on THERMAL || !THERMAL_OF
> -	select HWMON_LM75
>  	help
>  	  If you say yes here you get support for one common type of
>  	  temperature sensor chip, with models including:
> 
> Again running "make oldconfig" will do the right thing silently:
> 
> --- .config.old	2015-04-22 10:09:09.358164599 +0200
> +++ .config	2015-04-22 10:10:02.942263851 +0200
> @@ -2806,7 +2806,6 @@
>  # CONFIG_SENSORS_LM70 is not set
>  CONFIG_SENSORS_LM73=m
>  CONFIG_HWMON_LM75=m
> -CONFIG_SENSORS_LM75=m
>  CONFIG_SENSORS_LM77=m
>  CONFIG_SENSORS_LM78=m
>  CONFIG_SENSORS_LM80=m
> 
> This allows for a transparent migration to the new names from a user's
> perspective, as long as they do not jump directly from the original
> state to the final state. Maybe something like that can be done for
> CONFIG_I8K if you want to rename it.
> 

Hi, I already sent rename patch series, see [1]. And Greg will merge it
into 4.1-rc2, see [2].

[1] - https://lkml.org/lkml/2015/3/29/35
[2] - https://lkml.org/lkml/2015/4/21/429

-- 
Pali Rohár
pali.rohar@...il.com
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