linux-kernel - RE: [PATCH 09/12] platform/x86: wmi: create character devices when requested by drivers

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Date:   Thu, 21 Sep 2017 19:21:12 +0000
From:   <Mario.Limonciello@...l.com>
To:     <andy.shevchenko@...il.com>
CC:     <dvhart@...radead.org>, <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <quasisec@...gle.com>,
        <pali.rohar@...il.com>
Subject: RE: [PATCH 09/12] platform/x86: wmi: create character devices when
 requested by drivers

> -----Original Message-----
> From: Andy Shevchenko [mailto:andy.shevchenko@...il.com]
> Sent: Thursday, September 21, 2017 11:47 AM
> To: Limonciello, Mario <Mario_Limonciello@...l.com>
> Cc: dvhart@...radead.org; LKML <linux-kernel@...r.kernel.org>; Platform Driver
> <platform-driver-x86@...r.kernel.org>; quasisec@...gle.com; Pali Rohár
> <pali.rohar@...il.com>
> Subject: Re: [PATCH 09/12] platform/x86: wmi: create character devices when
> requested by drivers
> 
> On Thu, Sep 21, 2017 at 4:57 PM, Mario Limonciello
> <mario.limonciello@...l.com> wrote:
> > For WMI operations that are only Set or Query read or write sysfs
> > attributes created by WMI vendor drivers make sense.
> >
> > For other WMI operations that are run on Method, there needs to be a
> > way to guarantee to userspace that the results from the method call
> > belong to the data request to the method call.  Sysfs attributes don't
> > work well in this scenario because two userspace processes may be
> > competing at reading/writing an attribute and step on each other's
> > data.
> >
> > When a WMI vendor driver declares a set of functions in a
> > file_operations object the WMI bus driver will create a character
> > device that maps to those file operations.
> >
> > The WMI vendor drivers will be responsible for managing access to
> > this character device and proper locking on it.
> >
> > When a WMI vendor driver is unloaded the WMI bus driver will clean
> > up the character device.
> >
> 
> > @@ -44,12 +44,17 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/wmi.h>
> >  #include <linux/uuid.h>
> > +#include <linux/cdev.h>
> > +#include <linux/idr.h>
> 
> Keep alphabetical ordering.
> 

The existing list wasn't in alphabetical order.  I'll submit a patch in v2 earlier
in the series to sort and then put them in the right place for my patch.