linux-kernel - Re: [PATCH] Make all it87 drivers SMP safe.

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Message-ID: <BANLkTimeAh3pm=Z73hYPPfAJfu8J5=tPpw@mail.gmail.com>
Date:	Wed, 6 Apr 2011 17:35:07 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	Natarajan Gurumoorthy <natg@...gle.com>
Cc:	Guenter Roeck <guenter.roeck@...csson.com>,
	Jean Delvare <khali@...ux-fr.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Mike Waychison <mikew@...gle.com>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>
Subject: Re: [PATCH] Make all it87 drivers SMP safe.

On Wed, Apr 6, 2011 at 3:04 AM, Natarajan Gurumoorthy <natg@...gle.com> wrote:
> Guenter,
>      Thank you for your feedback. I found an easier way to deal with
> the it87_lock.c file. I do not need to move it to the driver/misc
> directory. The easier thing to do was to move the IT87_LOCK entry to
> the beginning of the drivers/watchdog/Kconfig file. This moves the
> entry before the "menuconfig WATCHDOG" entry. They use the exact same
> trick in drivers/misc/Kconfig file. The very first lines of
> drivers/watchdog/Kconfig file will look something like this:

Is the Kconfig even warranted?  I mean, if there is a shared resource
and it needs locking, then just apply the locking.   Where is the value
in adding another Kconfig?

Also the it87_lock.h file -- maybe you want to just call it it87.h -- then
if someone in the future cleans up the drivers and makes some macros
that can be shared across all the drivers, there is already a proper home
for such macros.  No point painting yourself in a corner and making the
file lock specific right from the beginning.

Paul.

>
> #
> # Watchdog device configuration
> #
>
> # This one has to live outside of the WATCHDOG conditional,
> # because it may be selected by drivers/hwmon/it87.c.
> config IT87_LOCK
>        bool
>        default n
>        ---help---
>          This defines the global lock needed by all IT87 drivers that
>          touch the Super I/0 chipset used on many motherboards. This
>          is needed to serialize access to the registers in SMP
>          systems. All it87 drivers will select this Kconfig option to compile
>          the lock into the kernel.
>
> menuconfig WATCHDOG
>        bool "Watchdog Timer Support"
>        ---help---
>          If you say Y here (and to one of the following options) and create a
>
> Regards
> Nat
>
> On Tue, Apr 5, 2011 at 8:02 PM, Guenter Roeck
> <guenter.roeck@...csson.com> wrote:
>> On Tue, Apr 05, 2011 at 10:50:47PM -0400, Natarajan Gurumoorthy wrote:
>>> Guenter,
>>>       Thank you for spotting the fact the everything goes south if you
>>> disable "watchdog". I am working on a solution. Looks like the ideal
>>> place to store it87_io_lock.c will be drivers/misc and the IT87_LOCK
>>> config will be placed before the MISC_DEVICES entry in
>>> drivers/misc/Kconfig file. This will be similar to the
>>> SENSORS_LIS3LV02D entry in that Kconfig file.
>>>
>> Almost, only afaik that is only used inside the misc directory, or at least
>> has some other components there. I don't really know how to handle this
>> situation correctly, except you could of course write a mfd driver to handle
>> the generic parts.
>>
>>>       Now going back to the partitioning do I send this change out as
>>> a multi patch set consisting of 4 parts something as below:
>>>
>>> patch 0 has a description
>>>
>>> patch 1 has only the lock and related files
>>>         drivers/misc/Kconfig
>>>         drivers/misc/Makefile
>>>         include/linux/it87_lock.h
>>>         drivers/misc/it87_lock.c
>>>
>>> patch 2 has drivers/watchdog changes
>>>         drivers/watchdog/Kconfig
>>>         drivers/watchdog/it8712f_wdt.c
>>>         drivers/watchdog/it87_wdt.c
>>>
>>> patch 3 has drives/hwmon changes
>>>         drivers/hwmon/Kconfig
>>>         drivers/hwmon/it87.c
>>>
>> Something like that. I have some doubts about using drivers/misc,
>> but I guess you'll get feedback on that after you submit the patch set.
>>
>> Thanks,
>> Guenter
>>
>
>
>
> --
> Regards
> Nat Gurumoorthy AB6SJ
> --
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