linux-kernel - Re: [PATCH 00/10] fujitsu-laptop: use device-specific data instead of module-wide globals

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Message-ID: <20170501130536.GA25546@marvin.atrad.com.au>
Date:   Mon, 1 May 2017 22:35:36 +0930
From:   Jonathan Woithe <jwoithe@...t42.net>
To:     Micha?? K??pie?? <kernel@...pniu.pl>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/10] fujitsu-laptop: use device-specific data instead
 of module-wide globals

Hi Michael

On Mon, Apr 24, 2017 at 03:33:24PM +0200, Micha?? K??pie?? wrote:
> fujitsu-laptop registers two ACPI drivers.  Whenever an ACPI device with
> a matching identifier is found by the ACPI bus, a new instance of the
> relevant driver is bound to that ACPI device.  However, both ACPI
> drivers registered by fujitsu-laptop access module-wide global data
> structures, assuming neither ACPI driver will ever be instantiated more
> than once.  While there are currently no indications of such issues
> happening in the wild, it is theoretically possible for multiple
> FUJ02B1/FUJ02E3 ACPI devices to be present in the firmware, which would
> cause two instances of the relevant driver to simultaneously access
> module-wide globals without any locking in place.  Also, modern Fujitsu
> laptops ship without the FUJ02B1 ACPI device present in firmware,
> causing memory to be needlessly allocated inside fujitsu_init().
> 
> To future-proof the module and lay the groundwork for separating the two
> aforementioned ACPI drivers into separate modules, move away from
> module-wide global data structures by using device-specific data
> instead.

Apologies for the delay in getting this first set of feedback to you.  It's
a combination of the extent of the patch set and a very busy week.

This patch set represents another worthwhile clean up of the fujitsu-laptop
driver.  While I sincerely doubt any laptop vendor will place more than one
FUJ02B1 (or FUJ02E3) in a single machine, removing the dependency on global
variables makes the driver self contained and more consistent.  I have some
points of clarification which I will post as follow ups to the respective
patchs.

Regards
  jonathan