linux-kernel - Re: [PATCH v2 12/14] platform/x86: dell-wmi-smbios: introduce character device for userspace

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Date:   Tue, 26 Sep 2017 22:10:11 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Mario Limonciello <mario.limonciello@...l.com>
Cc:     dvhart@...radead.org, Andy Shevchenko <andy.shevchenko@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org, quasisec@...gle.com
Subject: Re: [PATCH v2 12/14] platform/x86: dell-wmi-smbios: introduce character device for userspace

On Tuesday 26 September 2017 20:50:10 Mario Limonciello wrote:
> This userspace character device will be used to perform SMBIOS calls
> from any applications.
> 
> It contains 3 operating IOCTL's
> 1) sending a properly formatted 4k calling interface buffer.
> 2) Querying number of tokens in the given system
> 3) Copying the status of all these tokens to a properly formatted
>    userspace buffer.
> 
> This character device is intended to deprecate the dcdbas kernel
> module and the interface that it provides to userspace.
> 
> It's important for the driver to provide a R/W ioctl to ensure that
> two competing userspace processes don't race to provide or read each
> others data.
> 
> The character device will only be created if the WMI interface was
> found.
> 
> The API for interacting with this interface is defined in
> documentation as well as a uapi header provides the format of the
> structures.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@...l.com>
> ---
>  Documentation/ABI/testing/dell-wmi-smbios |  10 +++
>  drivers/platform/x86/dell-wmi-smbios.c    | 110
> +++++++++++++++++++++++++++---
> drivers/platform/x86/dell-wmi-smbios.h    |  28 +-------
>  include/uapi/linux/dell-wmi-smbios.h      |  55 +++++++++++++++
>  4 files changed, 165 insertions(+), 38 deletions(-)
>  create mode 100644 Documentation/ABI/testing/dell-wmi-smbios
>  create mode 100644 include/uapi/linux/dell-wmi-smbios.h
> 
> diff --git a/Documentation/ABI/testing/dell-wmi-smbios
> b/Documentation/ABI/testing/dell-wmi-smbios new file mode 100644
> index 000000000000..8ec98e9b7b34
> --- /dev/null
> +++ b/Documentation/ABI/testing/dell-wmi-smbios
> @@ -0,0 +1,10 @@
> +What:		/dev/wmi-dell-wmi-smbios
> +Date:		October 2017
> +KernelVersion:	4.15
> +Contact:	"Mario Limonciello" <mario.limonciello@...l.com>
> +Description:
> +		Perform SMBIOS calls on supported Dell machines.
> +		through the Dell ACPI-WMI interface.
> +
> +		IOCTL's and buffer formats are defined in:
> +		<uapi/linux/dell-wmi-smbios.h>

Should be "wmi" part of device name, even if whole driver work without 
WMI?

I think that "wmi" should be part of device name only if it is related 
to WMI bus functions, and not in case when it exports some vendor (Dell) 
specific API which may be implemented via WMI.

E.g. we have /dev/i2c-* for raw access to i2c devices. But we do not 
have /dev/i2c-something for e.g. RTC device connected via i2c...

-- 
Pali Rohár
pali.rohar@...il.com

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