linux-kernel - Re: [PATCH 2/2] hwmon: Allow to compile dell-smm-hwmon driver without /proc/i8k

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Date:	Sat, 28 Mar 2015 23:00:48 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Steven Honeyman <stevenhoneyman@...il.com>
Cc:	Paul Bolle <pebolle@...cali.nl>,
	Guenter Roeck <linux@...ck-us.net>,
	Arnd Bergmann <arnd@...db.de>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	Jean Delvare <jdelvare@...e.de>,
	Valdis Kletnieks <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: [PATCH 2/2] hwmon: Allow to compile dell-smm-hwmon driver without /proc/i8k

On Saturday 28 March 2015 13:54:51 Steven Honeyman wrote:
> On 28 March 2015 at 11:04, Paul Bolle <pebolle@...cali.nl> 
wrote:
> > On Sat, 2015-03-28 at 11:24 +0100, Pali Rohár wrote:
> >> --- a/drivers/hwmon/Kconfig
> >> +++ b/drivers/hwmon/Kconfig
> >> @@ -1703,6 +1703,17 @@ config SENSORS_ULTRA45
> >> 
> >>         This driver provides support for the Ultra45
> >>         workstation environmental sensors.
> >> 
> >> +config SENSORS_DELL_SMM
> >> +     tristate "Dell laptop SMM BIOS hwmon driver"
> >> +     depends ON X86
> > 
> > How did this past your testing?
> > 
> >> +     ---help---
> >> +       This hwmon driver adds support for reporting
> >> temperature of different +       sensors and controls the
> >> fans on Dell laptops via System Management +       Mode
> >> provided by Dell BIOS.
> >> +
> >> +       When option I8K is also enabled this driver
> >> provides legacy /proc/i8k +       userspace interface for
> >> i8kutils package.
> >> +
> 
> It's working OK for me (after fixing the mistake pointed out
> above).
> 
> [Latitude e6540]
> -----
> coretemp-isa-0000
> Adapter: ISA adapter
> Physical id 0:  +53.0°C  (high = +84.0°C, crit = +100.0°C)
> Core 0:         +51.0°C  (high = +84.0°C, crit = +100.0°C)
> Core 1:         +53.0°C  (high = +84.0°C, crit = +100.0°C)
> 
> i8k-virtual-0
> Adapter: Virtual device
> Processor Fan: 3171 RPM
> CPU:            +52.0°C
> Ambient:        +46.0°C
> SODIMM:         +40.0°C
> -----
> 
> Ambient and SODIMM look swapped - but it's probably just
> another Dell error. I really need to look at getting coreboot
> on this thing.
> 

Both patches do not change any code. So there should not be any 
type swapped with or without my patch.

Cpu type is requested via SMM in same way as it is doing old DOS 
executable. So there can be maybe problem in DELL SMM handler too 
or maybe just I did not understand correctly assembler dump of 
DOS executable...

> On 28 March 2015 at 10:24, Pali Rohár <pali.rohar@...il.com>
> wrote: ...
> 
> >  config I8K
> > 
> > -       tristate "Dell laptop support"
> > -       select HWMON
> > +       bool "Dell i8k legacy laptop support"
> > +       select SENSORS_DELL_SMM
> 
> ...
> 
> > +config SENSORS_DELL_SMM
> > +       tristate "Dell laptop SMM BIOS hwmon driver"
> 
> The only change I'd suggest is not to change the tristate to
> bool for I8K. Forcing that to bool means that
> SENSORS_DELL_SMM can't be compiled as a module if the user
> wishes to keep i8k hanging around "just in case". It'll
> probably annoy distro kernel packagers too.
> 
> 
> Thanks,
> Steven

My idea was:

SENSORS_DELL_SMM enable/disable compilation of kernel driver 
(ether statically link into kernel image or as external module)

CONFIG_I8K just enable /proc/i8k code in SENSORS_DELL_SMM -- no 
additional driver, just boolean switch which has effect only iff 
SENSORS_DELL_SMM is Y or M

-- 
Pali Rohár
pali.rohar@...il.com

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