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

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Message-ID: <CAHp75VcD+SK2sMMzx8VKed2vVtGJzdwTcM-a5FZyRidZL6jGYw@mail.gmail.com>
Date:   Thu, 21 Sep 2017 19:46:32 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Mario Limonciello <mario.limonciello@...l.com>
Cc:     "dvhart@...radead.org" <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.


-- 
With Best Regards,
Andy Shevchenko